The T3100SX was released in 1989 – in keeping with Toshiba’s rugged luggable design & chunky laptop form factor from earlier luggables models like the T3100 (1986) and T3200 (1987), the T3100SX weighed in at 15 lb (6.8 kg) and featured two large removable NiCD batteries. These large batteries allowed Toshiba to make the jump from AC powered plasma luggables to a truly portable battery powered device. Battery life, however, was relatively short at about 1 hour per pack (with all power saving functions turned off), but still with two cells (and the option to carry more) one could use the T3100SX for a full day in the field and not be tethered to an AC outlet. In 1989, this was cutting edge tech; a battery-powered luggable computer, with a crisp, clear, plasma display that was just about light enough to be used in your lap.

Fast forward just a few years later to 1992 and you can clearly see the concerted efforts of laptop manufacturers to miniaturise components bear fruit and was being done so at remarkable pace. The T4400SX has a thinner gas panel display, as well as a much smaller hard disk and floppy disk drive. These components did not only get smaller, but they were also simultaneously optimised for reduced power consumption. The result is that the T4400SX is less than half the size and weight of the T3100SX around just 2 years earlier at just 7.2 lb / 3.3 kg, and has twice the battery life. To top it all off the T4400SX had almost 7x more computing power in terms of MIPS with its 486SX CPU compared to the 386SX CPU on the T3100SX – and the CPU of the T4400SX was socketed, which means you could pop in any 5V 486 CPU such as the 486 DX, DX2 etc., to get even more computing power.

In terms of price, these two laptops were pretty much identical, with the T3100SX cost $5999 when launched in 1989, and the T4400SX launch price was $5899 in 1991. The most notable difference is that the T4400SX was maybe 5x more powerful in terms of processing power (maybe 10x if using a 5×86 drop in upgrade CPU), and weighed half as much as the T3100SX. This really shows quick technology was advancing in the late 80s and early 90s – your state of the art luggable laptop from 1989 was all but obsolete in just two years! I personally wasn’t quite an adult yet at during this time period, but now I can relate to why my parents were always complaining that they had to throw out our expensive PC every few years. Technology was just moving so fast!

Here are their specifications:

T3100SX

• Dimensions 360 x 310 x 80 mm (W x D x H)
• Weight: 6.8 kg (15 lbs)
• CPU: 386SX, 16 Mhz
• Max RAM: 13MB (proprietary ram modules)
• Battery Tech: Two NI-CD batteries, lasts about 45 minutes each with constant use, no power saving features enabled.
• Display: VGA, 16 colors of grey / orange.
• Video Chipset: Likely a PVGA
• Video RAM: 256Kb
• Ports: Serial, Parallel, Modem & Toshiba Card
• Floppy Disk Drive: Yes
• Expansion: None – No ISA or docking station / port
• Hard Disk: 40 / 80 MB
• Notes: The 16 Mhz Intel 386SX can be de-soldered and upgraded with a 5V tolerant chip such as the TI 486 SXLC2

T4400SX

• Dimensions: W 297 x 210 x 56 mm (W x D x H)
• Weight: 3.3 kg (7.2 lbs)
• CPU: Socketed 486, upgradable to AMD 5×86 / Cyrix 5×86.
• Max RAM: 18MB – 2MB onboard, 16MB through credit card style memory.
• Battery Tech: One NI-CD battery, lasts about 1 hour with constant use, highest speed settings, brightness set to max, no power saving features enabled.
• Display: VGA, 640×480 16 colors of grey / orange. Ultra slim, low power consumption model for laptop use, similar to the display in the T6400.
• Video Chipset: Paradise PVGA1F (aka Western Digital WD90C23)
• Video RAM: 256Kb
• Ports: VGA, Parallel, Serial, Mouse PS/2
• Floppy Disk Drive: Yes
• Expansion: Expansion bus for docking to Toshiba Deskstation IV to use ISA cards.
• Hard Disk: No restrictions, will take CF / Disk on Module with most up to date BIOS. Stock is 80MB.
• Notes: Has a non-standard, pre advanced power management ‘resume’ function, only works on MS-DOS, and can be modified to work with Windows 3.1x but will not work with Win 95

In terms of retro computing – my favourite is definitely the T4400SX hands down. I would say it’s form factor still resembles that of a modern laptop. It can be upgraded to run Windows 95 (and quite snappily too through it’s 486 CPU socket, which will happily accept a low profile 5×86 CPU upgrade), uses credit card style memory cards giving up to 18MB of RAM, and can even be overclocked (more on that in a future post!)

The only thing that holds it back (a tiny bit) is that it’s auto-resume function was never updated to run with Windows 95 and it’s associated version of DOS, which is a shame, though even in DOS 6.22, the auto resume takes a while to load, sometimes longer starting from a cold boot, so it’s not all that useful. Also it’s on board video memory remains at 256K – this is fine for DOS, but in Windows 95 you can ‘trick’ games that need 256 colors to run on a gas plasma display computer if you have 512Kb of video memory – something that I discovered was possible on the Toshiba T6400DX.

I’ll circle back and add more photos here of the mods and upgrades, and some more shots of games 😀

And that’s pretty much it! Did you use either one of these computers back in the day? What kind of work did you do on it? Let us know in the comments!

The post Battery Powered Gas Plasma Laptops appeared first on Retropaq.

The T6400 still sits on my desk and is one of two Toshiba laptops that I use often (the other being my Toshiba Satelite 4005 CDT). The T6400 has a special place in my collection as it’s the one of the fastest 486 portables in my collection (currently running an AMD 5×86 133 Mhz) and it somehow has hardware contrary to what is listed in it’s specifications, most importantly, that it has 512KB of video RAM. This allows the running of 256 colors (despite the built-in plasma only offering 16 shades of grey). This unique combination means that I can get games that require 256 colors under windows 95 to run on the internal gas plasma screen and not throw up error messages. It also doesn’t hurt that it has 36 MB of RAM from the two memory cards installed.

The Gas Plasma Display & Video Chipset

Both the T6400 and the Toshiba T6400C use a Western Digital / Paradise chipset – specifically, the PVGA1F (WD90C23). There are several interesting things about the T6400’s graphics capabilities:

• The T6400 and the T6400c use the same screen connector, (and I suspect, actually identical motherboards) and the screens are interchangeable between the two different models.
• The T6400c actually has 512K of video memory, not the 256k as described in literature from Toshiba and I am pretty sure the T6400 also has an identical amount of video memory. This has some interesting consequences for the built in gas plasma screen.
• The internal gas plasma display panel can only display 16 colors (shades of grey / orange), and maxes out at a resolution of 640 x 480. However, because the amount of VRAM that the video chipset has, it is capable of displaying 256 colors at 640×480 resolution.
• The T6400 / T6400c (along with the T4400 and other similar laptops that are designed to run a greyscale LCD or gas plasma display), have a built in color grey scale controller gate array. This chip along with other chips in the video chipset ‘converts’ color values to 16 shades of grey to be displayed on the internal display, while the external video can display 256 colors (at 640 by 480).
• Since the graphics card has 512k of video memory, the computer is capable of using VESA drivers (like univbe) to run DOS and Windows software that require 256 color modes.
• Interestingly, this means that the T6400 with a 16 color / shade gas plasma display functions properly in 256 color modes. Software (including Windows 95) will run in 256 color depth, and the colors to be displayed are remapped by the hardware into the closest matching 16 shades of grey.
• As far as I am aware, this means that the T6400 is the only gas plasma laptop / portable that (without any hardware modifications) natively runs games and software needing a VESA driver – this means you can run a whole bunch of early to mid 90’s DOS and Windows 95 games that normally would require 256 color displays to run. The onboard color to ‘grey’ scale converter will translate 256 colour output into one of the 16 shades of ‘grey’ on the plasma display. Check out my screenshots below! The color-to-greyscale mapping hardware typically does a very good job at remapping the normal colour pallete used by the software into the 16 shades of grey / orange used by the gas plasma display. How cool is that?!
• Note that the T4400SX / T4400SXP (the only T4400 variant that is offered with a gas plasma display) has almost identical hardware to the T6400 (aside from the ISA slots) but with one main difference. The T4400SX only has 256KB of video memory, meaning that it is not VESA compatible, and is limited to a color depth of 16 colors in Windows 95 (unless you use scitech’s display doctor version 6, but the display will be garbled as there is not enough video memory (300KB minimum) for 256 colors. Full write up on the T4400 series coming soon.

CPU Upgrade

Upgrading the CPU is fairly easy – it’s ZIF socket 486, so most 486 CPU’s can be dropped in with ease. However, the socket voltage is 5V, meaning if you want to use later 486’s you will need drop-in upgrades that have an on-board voltage regulator. Additionally, due to the limited height clearance, only QFP style 486 upgrade CPUs will fit. Others that have a large heat-sink, or that use a ceramic 486 with a traditional interposer and voltage regulator board will be too thick and the cover won’t fit. To be on the safe side, I also added a thin copper sheet to the cover of the CPU to act as a makeshift heatsink, for the AMD 5×86 which hopefully allows for increased heat dissipation. This seems to work just fine, but be careful as bare copper can conduct electricity and create shorts if you are not careful.

The performance boost that comes from the drop-in CPU upgrade is substantial, however, the system is still held back by it’s built-in graphics chipset, and unfortunately there is no way to upgrade this as it’s on the system board and is used to drive the gas plasma screen. Oh, and for those with keen eyes, you will notice a removable CPU clock crystal daughterboard- don’t try and overclock this computer – I tried with a plethora of crystals (over 10), with resulting clock speeds from 33 Mhz up to 80 Mhz – none of them worked except the 33 Mhz one that came with the computer. Further research indicates that the onboard controller gate array chip (used in the T4400 as well) can only operate at 16, 25 or 33 Mhz, so 33 Mhz is the only way to go.

Memory

The Toshiba T6400 accepts two ‘credit card’ style RAM cards. These were manufactured in various capacities (2MB, 4MB, 8MB and 16MB), by different manufacturers (Kingston, Toshiba and perhaps others). The T6400 can operate with two 16 MB RAM cards installed for a total of 36MB (4MB onboard, plus 16MBx2), allowing the T6400 to run memory intensive applications, and Windows 95 is quite snappy and responsive. Here’s my first test with 28MB (24 on card plus 4 on the system board).

Expansion Slots

The Toshiba T6400 comes with one built in ISA expansion slot that can fit any full length ISA card. To maximise expandability, I chose to install a dual slot Vadem ISA to PCMCIA adapter, which allows me to use two PCMCIA cards simultaneously. Since the hard drive is limited to specific models and the largest is 200MB (unless you choose to use dynamic drive overlay software and go the CF / SD adapter route), and I am running Windows 95, I have a 1 GB compact flash card permanently inserted into slot 1 (the lower slot) and then in the other slot I can choose between my Panasonic CDROM / Sound Card combo or my PCMCIA network adapter.

The setup above works flawlessly in Windows 95, drivers were automatically installed for the PCMCIA slot. However, there are some quirks when using the seemingly rare dual PCMCIA adapter with the Vadem chipset in dos. For one, if you are using a PCMCIA to CF Card, it seems to only work in the lower slot (my guess this is slot 1). Inserting the card above into slot two doesn’t seem to work, no matter what settings I tried, which is a bit annoying.

Additionally, it was also quite the chore to get both the PCMCIA CD-ROM driver and the PCMCIA CF Card drivers working simultaneously in dos. If anyone out there is trying to get PCMCIA working in dos, here is the configuration that I used for here’s the software I used and my config.sys and autoexec.bat files, along with the CardWiz and CDROM files needed. In the ZIP are the individual files and the folders needed, just add this to a DOS 6.22 or Win 95 setup.

Download CardWiz, Config.sys, Autoexec.bat and CDrom Drivers for my T6400 Setup.

Floppy Drive

If you have a retro Toshiba laptop of an early to mid 90’s vintage, you might have noticed that the floppy drive does not work – many of these computers come with a Matsushita branded slim-line internal floppy drive. These unfortunately are rubber belt driven, and as time does it’s thing the rubber belts essentially disintegrate and turn into a sticky gooey mess. I was fortunate enough to have a working drive when I obtained my T6400, so I was able to install all the drivers for the PCMCIA adapter and other software before the floppy failed. I’m currently waiting for my replacement belts to arrive, hopefully they are a right fit as apparently these drives variants are commonly used across the Toshiba lineup and they are very particular about the belt size and thickness as noted here.

EDIT: the replacement belts that I ordered above worked, but I had to mix and match parts of 3 different drives to get it working reliably. These drives are somehow very sensitive to the belt’s dimensions. A belt that is too thick or thin may not properly stay looped onto the motor and disk drive. Slight differences in belt length (diameter) will affect the rotational speed of the drive. After tinkering with it however, it’s been working fine (reading, writing, formatting disks) for the last 6 months with no problem and the belt seems firmly in place.

The Result

Well – having upgraded my Toshiba T6400 with gas-plasma display to the specs below let’s see how far we can push it:

• 36 MB of RAM
• AMD 5×86 running at 133 Mhz (with improvised copper sheet heat sink to dissipate the extra heat)
• 200 MB HDD – I kept this stock as the drive seems ultra reliable and you just can’t replace those hard drive sounds 😉 – additionally, the T6400 BIOS will only accept a very limited range of hard drive models made by Conner.
• ISA to PCMCIA adapter with:
  • CDROM & Sound Card Combo (limited sound through a Panasonic external KXL-D745 SCSI PCMCIA combo CDROM & ISS sound card, music only in dos, some sounds in Windows).
  • A ‘permanent’ 2GB CF card, used to store working game & software files & backups – I only use this card to hold games, programs and backups to help ensure it does not get corrupted. The OS’s (Dos & Windows 95 are on the HDD (C:), so if I want to copy software to the T6400 I use a scratch / other CF card to copy software to the actual hard disk, then I copy the software from that onto the ‘permanent’ CF card.

What games can we get to run, and how playable are they (considering game speed and graphics legibility)? Again most of these games require 256 color modes to run, and have their 256 color palletes converted to 16 shades of grey. On top of that the screen is not 16 shades of grey, but 16 shades of not so distinct orange, so the playability / legibility of graphics is obviously not going to be as good as it would be in real 256 colors. However it is quite a novelty to see these mid-to-late 90’s games running on hardware that is really not supposed to be supported.

Windows 95

Grand Theft Auto (1997)

The original GTA does works in 8 bit color mode – as I am using the Panasonic PCMCIA sound card / CD-ROM combo, I can’t get FM Synth in dos and some windows games. However the radio / music does work just fine. The game is a bit laggy as one would expect on this hardware, but it surprisingly it runs well enough to be just about playable.

Command & Conquer RED ALERT (1996)

Red Alert runs surprisingly well, even the pre-game videos and animation play at an acceptable frame rate.

Civilization II

This is perhaps my favourite strategy game, and I think my favourite game overall from the 90s. I spent hours and hours playing this game as a kid. Not only is it highly addictive and well designed, every game plays out differently so the replay-ability factor is 10 out of 10. Despite the 256 color pallete used in the original game being quite colorful (as in almost all 256 colors are used), the remapping hardware does a great job at translating the 256 colors into 16 shades of grey.

However, most laptops / luggables with a gas plasma display are only equipped with 256K (or less) of video ram, and the remapping done by Windows 95 under 16 color mode uses alot of dithering and makes the game almost totally illegible and unplayable. Being that this is my favourite game, I have created a special set of graphics and palette files that optimises the remapping of the 256 colors used by Civilization II into more a more legible 16 shades greyscale / shades of grey / orange. I created this by editing the files in a Win 95 version of Paint Shop Pro. You can chose to run Civ 2 on a T6400 with a 16 shade gas-plasma display in 256 color mode, which remaps the pallette without dithering, or you can switch to 16 color mode and use my custom palette (more legible flag colors, better terrain visibility etc., than the default 256 to 16 shade remapping.)

Note, this palette is needed to run the game with on the Toshiba T4400SX without dithered graphics, as the T4400 can only support 16 shades of grey, with 256 color palettes being dithered to being unplayable. You can download the 16 shade gas plasma optimised palette and associated updated graphics files for Civ 2 here.

Transport Tycoon Deluxe (1995)

Settlers II SVGA in DOS (1996)

Doom Ultimate / Doom95 in 640×480 resolution (1996)

Quake / WinQuake (1997)

Simcity 2000 for DOS in VESA (1993)

Master of Orion II (Win 95)

The post Upgrading & Tweaking the Toshiba T6400 Laptop appeared first on Retropaq.

[Hero Image of Toshiba T6400, 80’s photoshoot]

Also by 1992, two years on since the release of the P75, laptops had clearly demonstrated they were the path to the future, and luggables had become viewed as unnecessarily large and cumbersome for most users. Expansion slots were pretty much the only reason one would still tote around a luggable, though the PCMCIA card has just been launched and would soon offer ISA and Microchannel cards a run for their money. All this meant that manufacturers had to develop the last generation of luggables to still be appealing and justify their heft. Benefits touted of a late-generation luggable were that it was to be your only PC, meaning that all your files and programs were on one device – eliminating the painful syncing of files through floppy disks that laptop owners typically had.

Additionally, in 1992 if you wanted a color LCD and a 486DX, you pretty much had to settle for a luggable – though the Toshiba T6400’s baby brother, the T4400SXC would demonstrate to many in ’92 that settling for an SX processor was a wise trade-off to access the tremendously lighter and compact laptop form factor, even if you were still rather limited by the paltry 2-hour battery life.

[Competing Color Laptops & luggables from 1992 – Magazine]

So enough preamble – enter the Toshiba T6400 – marketed by Toshiba to be “a mobile computer that behaves like a fully equipped high-end desktop machine”. Perhaps not a super catchy slogan, but Toshiba knew that some people would pay for the killer combo of the fastest processor combined with their favorite ISA card.

Several model variants were offered though the key differences were down to the processor (socketed 486 SX or DX) and display (active-matrix TFT LCD or gas-plasma). The color display model seems to have been far more popular than the plasma variant judging by eBay listings in 2022 – I have only come across one T6400 configured with a plasma display – this underscores the fact that plasma displays were definitely on the way out in ’92 and were yesterday’s technology. This made total sense as color displays had come a long way from their pioneering days a few years prior – just take a look at this Toshiba grand-daddy – the ultra-rare Toshiba T5200c – an STN-LCD with 16 extremely murky colors. 256 active-matrix color displays were now the norm, and gas-plasma had no real advantage other than price.

[Color T6400 & Plasma T6400 image]

Perhaps the main reason why the T6400 is my favorite plasma luggable is that for some odd reason, the Toshiba T6400’s graphics controller’s driver will report that it has 256 colors at it’s disposal under DOS Windows 95, meaning that it is perhaps the only gas plasma computer that can natively run 256 color games – take a look at these 256 color classics running in 16 shades of brilliant orange:

If anyone knows how the T6400’s graphics card can do this, please, please let me know in the comments below!

Another neat party trick the T6400 has is its removable keyboard – allowing you to have your luggable on the table and only the keyboard on your lap – essential for gaming – I mean working on excel late at night

[T6400 running Win 95 Game on coffee table with the keyboard on lap image]

More important than the removable keyboard however is the fact the T6400’s CPU is socketed, meaning, that a low profile 486 CPU upgrade can be installed, though I have modified mine a bit by adding a custom heatsink to the cover to allow for enough heat dissipation.

[T6400 open with CPU shot]

To truly transform my T6400 into a true Windows 95 retro-gaming battle station, I added a 2-slot ISA to PCMCIA adapter, which gives me a slot for a CF card (which is needed due to the slightly limiting 200 MB hard disk) and a slot for either my ethernet card or my CD-ROM / Sound Card combo (switched out depending on if I am installing files from network or playing games).

Other than these amazing features and the typical floppy drive, the T6400 sports pretty run-of-the-mill connectors, including two PS/2 ports, an external floppy connector, serial, parallel, and VGA out. It also has a proprietary external expansion adapter, as did most Toshiba laptops of the time, though I have yet to ever see what these ports were actually supposed to connect to (allegedly, they were used with an external ISA backplane-in-a-box to allow for even more expandability.) RAM was expandable from the stock 4 MB to up to 28MB through credit card style RAM cards, though I was unable to install the maximum of 32MB of RAM no matter what combination of appropriate RAM cards I tried. I suppose, however, that 28MB is more than adequate for this setup. To top it all off, the T6400 has a rather smart built-in carrying handle, similar in design to that of the Macintosh Portable, allowing for easy transporting of this beautiful luggable briefcase computer.

[T6400 being carried by handle, closed with black pant leg with background]

Overall, I think the Toshiba T6400 (and also to a lesser degree the T4400) are elegant and well-constructed. The feature set of the T6400 would still have been impressive compared to early laptops in the final days of the luggable. If you had a T6400, please leave your comments below – we would love to hear your stories on how you used this amazing computer back in the day.

Posted NYE 2022 – Happy 2023 to you all!

The post Toshiba T6400 – The Last (& Best) Gas Plasma Portable appeared first on Retropaq.

However, the usual disclaimer applies: WARNING, HIGH VOLTAGE – Plasma displays operate at voltages around 100 – 300 volts or more. Take proper precautions when handling. Capacitors may be present that can electrocute you even after mains power is unplugged. Continue at your own risk!

Now that’s out of the way, we can get down to business. Generally, gas plasma display issues can be categorized by the following faults:

1) No illumination of the panel 

This can be the result of a faulty connection, a bad (out of voltage) PSU, a PSU that is not generating the right frequency signal gas plasma displays need to operate, physical damage to the plasma display panel itself, or a bad motherboard/graphics card. If you have a computer or portable that seems to boot (either through it giving a beep indication during POST or through hooking up an external monitor) but still nothing comes up on the plasma display, I would check the signal and power cable connections and clean them with contact cleaner, then check the functionality of the graphics card (by confirming there is an image on an external monitor), then check the PSU voltages. I would then recap and check the driver board on the rear of the display. If the plasma display still fails to illuminate, then I would check for any broken glass, as there is a glass nipple on the rear of the unit that can sometimes break off. If this is the case the plasma display is irreparable and typically cannot be revived. Save time and frustration by simply obtaining a replacement panel from a donor unit. 

2) “Dead” (un-illuminated) horizontal or vertical lines and/or “Bright” (over-illuminated) horizontal or vertical lines

These two symptoms are quite typical in older gas plasma display panels. Both are caused by faults in or on the driver ICs that line the edges of the rear of the plasma display panel. In some cases when dealing with a horizontal line, you may have to “unfold” two flaps on either side of the display to get to the horizontal driver ICs. Very seldom are blank or bright lines caused by a faulty graphics card, or a faulty cable (The proper functioning of the two aforementioned items can be determined by hooking up to an external display – if there are no errors, you can be pretty certain it is the plasma display panel). To attempt a repair, first, remove the plasma display from the computer. Secondly, using isopropyl alcohol or contact cleaner, carefully clean the solder joints that attach the driver ICs to the plasma display with a cotton bud. In some cases, there may be rust or other debris that are causing shorts leading to the bright, over-illuminated lines. In other cases, bad solder connections from the ICs to its solder pad (or other breaks in continuity elsewhere) can lead to dead or blank lines. Check each IC for faults visually (and if you have the ability and patience, check for continuity if possible).

Be very careful when cleaning or attempting any soldering repair as the IC driver pins are very fine and are also sometimes soldered onto plastic flex-cable which melts very quickly when exposed to the heat of a soldering iron. All this being said, it is also likely that the defect causing the fault on-screen is within a / several IC driver chips themselves, in which case, the ICs would need to be identified and then swapped out for a replacement one. I have yet to attempt this myself as obtaining a replacement screen is generally not that difficult or cost-prohibitive.

3) Burn in or other screen defects

These are typically caused by wear and tear – can show up as ghosting, darkened patches, and other similar anomalies. Unfortunately, these cannot be repaired. If they bother you, then your best option is to replace the screen.

Overall, plasma display panels are not really serviceable components. Recapping the driver PCB typically does not resolve any issues, and trying to solder/repair driver ICs requires specialized soldering equipment and steady hands. Generally, I don’t mind a couple of lines on gas plasma displays – I feel they give the computer a little character. If the screen defects bother you, then your best option is simply to replace the display panel. If you have managed or have attempted to repair a gas plasma display, please comment and share your thoughts below!

Check out other posts related to Gas Plasma Displays:

• 
  Battery Powered Gas Plasma Laptops
• 
  Upgrading & Tweaking the Toshiba T6400 Laptop
• 
  Toshiba T6400 – The Last (& Best) Gas Plasma Portable
• 
  Repairing Gas Plasma Displays
• 
  The Chronicles of Gas-Plasma

The post Repairing Gas Plasma Displays appeared first on Retropaq.

EDIT: If you’re looking for tips on how to REPAIR gas plasma displays, check out this post.

Aside from the look, however, the gas plasma display is a miracle of creative engineering. What is so miraculous, you may ask? Well, consider these fundamentals:

1. A gas-plasma display is basically a large, flat, very sophisticated neon gas lamp. The display unit’s light is generated (discharged) by the same principle that gives neon signs their glow and distinctive orange color.
2. The glow given off by gas-plasma lamps has been used as display technology as pixels since 1927, way before digital computers were invented (more on that below).
3. The picture quality is superb, especially when considering the time period when these displays were used in portable computers and industrial equipment. Gas plasma displays were advertised as having a contrast ratio of 100:1 – outperforming LCDs from the early ’90s. Furthermore, the wide-viewing-angle and lack of blur (fast response time) made them ideal for high-end computer & GUI use.
4. Plasma displays were expensive – opting for the plasma screen option on a laptop could have added about US$500 – US$1000 to the sticker price over LCD.

What is gas-plasma and how does it work? 

The glow given off by a gas-plasma display is the same glow that is generated when a neon (gas-plasma) bulb is turned on; electricity is passed into a sealed space that contains primarily neon gas – other gases can also be used, but it is neon that gives an orange glow.

When an electric current is applied to the positive and negative terminals, sufficient energy is provided to remove an outer electron from the neon atoms (ionization). The positively charged neon atoms are then attracted to the negative terminal, and the free electrons are attracted to the positive terminal. These charged particles (ions) move and bump into other atoms and generate heat and light. Each atom bumping into an electron produces one ion and two electrons, resulting in a chain reaction (aka Townsend Avalanche).

This luminous electric ark, aka, “plasma,” is electrically conductive; as it is formed, the circuit is completed. Once plasma occurs, a lower voltage is supplied to keep the chain reaction going, and to turn off the bulb, the circuit is broken (eg., through a switch). 

How is gas plasma discharge used in a display? 

A gas plasma display can be thought of as thousands of miniaturized gas plasma lamps arranged together into a grid or a “matrix”. Each tiny “bulb” is a cell (or pixel) within the screen and is full of neon gas.

Cells are electrically connected via silkscreen electrodes that run to the edge of the glass screen. The control of these pixels is directly controlled by the driver card – a PCB that typically is attached to the plasma display unit itself.

This driver card interprets the computer’s output signals to switch on and off specific pixels on the screen and generates the high voltages needed for plasma to occur through an inverter.

Noteworthy Gas Plasma Displays

1927 Bell Labs Neon Gas Plasma Display for Mechanical Television

Some might consider it a bit of a stretch to say that a matrix of bulbs arranged in a grid can be called a screen. But, since each bulb can be controlled (it can be on or off), it acts much the same way as pixel does on a modern display. Therefore, if you have enough bulbs (pixels) in a large enough grid, you can manipulate them to generate the appearance of an image – and this is what took place in 1927. 

Bell Labs had developed a mechanical television (itself a fascinating device,) but equally important, they had also developed this rudimentary screen to display a moving image. It is not known how “clear” the image was on the screen as no photos exist of it in operation. However, descriptions indicate that the audience was able to discern individuals who were being shown on the screens. Incidentally, a similar technique of using bulbs in a grid as a display was developed in New York for “The Zipper” – a 380-foot long ribbon of 14,800 incandescent light bulbs used to display news stories as moving text. 

1967 PLATO (Programmed Logic for Automatic Teaching Operations) 

PLATO was a computer education system developed at the University of Illinois in 1960 using mainframes and CRTs. Its development heralded what was to come in multi-user computer systems: forums, message boards, online testing, e-mail, chat rooms, picture languages, instant messaging, remote screen sharing, and multiplayer video games – all can be traced back to the PLATO system. By 1967, researchers took the system a step further and had perfected the first plasma display by sandwiching a mesh of electrodes between 2 plates of glass filled with neon. The first commercial gas plasma displays (“Digivue”) were manufactured by Owens-Illinois in 1971, a prominent glass & CRT tube manufacturer for use in the PLATO system. These early gas plasma displays were A/C powered in order to take advantage of how the plasma behaved – it could be used as a type of memory for the display. This eliminated the need for expensive memory ICs (RAM) to drive the display, lowering costs, making the plasma display competitive against CRT technology. 

1975 SAI Plasmascope

As with most new technologies, the military was involved in the development of gas-plasma. In 1975, SAI Technology Company unveiled “Plasmascope” an “inherent memory display terminal” for military use. Selling points included a lack of jitter and flutter that CRTs exhibited in tough conditions, and that there was no maintenance needed on the unit. These displays were sold at “under US$20,000 each in [order] quantities of over 100 units“, and were used in numerous military applications including ground launch cruise missile control systems.

1983 IBM 3290 

Before laptops, portables, and personal computers took off, IBM had already developed and utilized plasma display technology for its mainframes and terminals. The IBM 3290 was a high-function, large capacity, plasma-panel display station attached to a 3274 Control Unit, and, like the PLATO, the plasma display was used as a type of memory for the screen. A member of the 3270 Display System family, the 3290 could display up to 9,920 alphanumeric characters in multiple-screen format options for entering data into and retrieving data from mainframe computers such as System/370 Processors, 4300 Processors, 9370 Processors, and 8100 Information Systems.

1985 Gridcase 3

Made with an indestructible magnesium-alloy case, the Gridcase 3 by GRiD Systems Corporation was a heavy-duty rugged laptop used by the military, governments, and fortune 500 companies. It featured an 8086 based CPU and a 640×400 gas plasma display. The display could support 25 lines and 80 columns of text. These bad boys were expensive – setting you back a cool US$4350 in 1985 (equivalent to over US$10,000 in 2020).

1986 Toshiba T3100 

The Toshiba T3100 was a 286-based clamshell portable and is noted as being the first IBM “AT-class” portable. It was CGA compatible with its 640×400 gas plasma screen and could also support a special T3100/AT&T 6300 640×400 high-resolution graphics mode. Reviewers at the time praised the T3100 for its exceptionally clear and legible display and relatively light weight (for a portable).

1986 Compaq Portable III (CGA)

Compaq released the Compaq Portable III to replace it’s gigantic CRT-based Compaq Portable II – and it was a great commercial success. Featuring a 640×400 gas-plasma screen that supported CGA and MDA modes, this 286 based computer was well built, and well-received by critics despite it’s premium price tag. 

1987 Compaq Portable 386 (CGA)

The Compaq Portable 386 was released a year later and was an upgrade of the Compaq Portable III (above). It featured a 386 CPU; making this little lunchbox computer the fastest portable computer when it was released. It retained the same 640×400 gas-plasma screen that supported CGA and MDA modes as the Portable III, which unfortunately hastened its obsolescence as VGA became the new standard. 

1989 Toshiba T3200SX

Toshiba’s T3200SX pushed the laptop form factor to its limits. This 17.5-lbs (8 KG) portable computer had a clamshell form-factor like a modern laptop, but it is unlikely that anyone placed one of these knee-crushers on their laps. Performance-wise, however, the Toshiba T3200SX was a heavyweight screamer, performing more like a desktop computer with it’s VGA graphics, 16 shades of “grey,” and 386SX CPU. 

1990 IBM P75

The IBM P75 and its younger brother, the IBM P70, were both gas-plasma portables that sported a 640×480 VGA gas plasma screen, which supported 16 shades of “grey”. These machines were quite advanced for the time and were referred to as “portable servers” with the IBM P75 being the first portable 486-based computer available for sale in the US. However, their size, weight, and cost prevented them from being widely adopted.

1992 Toshiba T4400SX and Toshiba T6400DX 

The Toshiba T4400SX and the Toshiba T6400DX were among the last consumer laptops/portables to be offered with a VGA gas-plasma display. The T4400SX is also noteworthy for being one of the few battery-powered laptops to use a plasma display, as typically batteries of the time could not keep a power-hungry gas-plasma display running for long.

Then, in late 1992, the IBM Thinkpad 700c was released – one of the first mass-market laptops with an active-matrix thin-film-transistor (TFT) display. Active-matrix TFTs mitigated the ghosting problems on older, passive-matrix color displays. This was the nail in the coffin for the 16-shade-of-“grey” gas-plasma as there was now no advantage – crisp, clear & portable color technology had finally arrived.

The IBM 700c and other laptops that followed got rave reviews, and understandably so – take a look below and you can see first hand how bad the ghosting and poor contrast of a passive matrix screen really was.

And that brings us to the end of our abridged history of gas-plasma screens. But wait there’s more, (of course)! Gas plasma lived on after it was phased out of laptops, as the technology went on with LCD to replace CRT televisions. CRTs just could not handle large screen sizes well; 42 inch CRTs were comically gigantic, though they arguably had better picture quality at the time.

In fact, during the heyday of Plasma TVs, Panasonic came out with a 152″ plasma TV (more like a plasma “wall”), though plasma TVs couldn’t hold out forever.

Manufacturers eventually threw in the towel, with most factories ceasing production in 2015. Plasma display technology is today considered obsolete as it has been superseded by advances made by LCD and OLED technology.

The post The Chronicles of Gas-Plasma appeared first on Retropaq.