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This month I want to cover a topic that some of us have came across from time to time.

You get an old Atari 8-bit computer and you find little switches that are not part of the original system and you wonder what they do.

On the Atari 400 some of the more common upgrades were the replacement keyboard from membrane to regular style keys and memory enhancement beyond the 16 KB. On the Atari 800 you had multiple OS ROMs that could be piggy backed, memory upgrades beyond the standard 48 KB. There have been many add-on devices like SCSI and IDE hard drives as well as true hardware reset switches.

The 800XL and the 130XE had all of the above and more. You could get a 80 column display and a 256 KB RAM disk with some of the various upgrade as well as a dual or triple OS ROM installed via a toggle switch.

[Photo: Atari 800XL]
Atari 800XL

Let's look at a typical 800XL with these enhancements. A few months back I added another 800XL to my collection. I noticed two additional switches and decided to go inside to see what they were for. The unit would power up but not give a display. I thought there might be loose chips in the mainboard so I had more than one reason for wanting to go inside.

[Photo: 800XL with front cover removed]

After removing the screws I opened up my Atari 800XL and unplugged the keyboard cable. I immediately saw the add-on cable on the right side running from the back of the case and going under the RF shield and mainboard.

[Photo: 800XL wires for hardware reset switch]

[Photo: 800XL solder joints for hardware reset]

On the back side of the board the cable was soldered and I discovered this was a true hardware reset switch, unlike the standard soft reset on the Atari 8-bit systems.

[Photo: 800XL toggle switch for dual OS]

[Photo: 800XL dual OS piggy backed]

The other was a toggle switch that went down through the RF shield and was tied into a dual OS chip. Since the factory chip was on top, I was not sure as to what the second chip might be. Since there were several chips made in this manner I could not begin to guess which one this was.

While looking at the mainboard I discovered additional rework that appeared to be a "home brew" 256 KB memory upgrade from the stock 64 KB.

[Photo: 800XL home brew 256KB upgrade top side]

[Photo: 800XL 256KB upgrade continued]

[Photo: 800XL 256KB upgrade bottom of motherboard]

I looked at various old upgrade articles I had and was not sure which one this might be, so I sent a photo to my friend Rick Detlefsen to get his opinion. Rick felt it was just the standard home made 256 KB upgrade. While I was in there I reseated several chips (this mainboard was an older one with most of the chips in sockets instead of being soldered to the board).

I reassembled the computer and powered it up.

[Photo: 800XL screen showing Omniview 256 OS]

The system came on just fine and the second operating system turned out to be the Omniview 256 by David Young. This OS allowed not only an 80 column display, but the ability to have a 256 KB RAM disk (providing your computer had the memory upgrade as well).

So the mystery had been solved. This old Atari 800XL had a 256 KB memory upgrade, a dual OS upgrade and the hardware rest switch added on by a previous owner.

Atari 800
When I finished the 800XL, I did the same thing to my older 800, and found a toggle switch to turn off the speaker, a memory upgrade, a switch to disable the left cartridge slot, dual OS and a hardware reset. There was also the add-on
Busi-Key by CT systems which connected to the keyboard connection inside.

[Photo: 800 OS board with dual OS]

[Photo: 800 with left cartidge rework]

[Photo: 800 memory board with RAM upgrade]

[Photo: 800 hard reset switch wired to board]

[Photo: 800 hard reset switch wired]

[Photo: 800 keyboard connection to add-on Busi-Key]

[Photo: 800 system after reassemble]

I'll see you next month at Atari in the USA 2002.

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MyAtari magazine - Feature #9, August 2002

Copyright 2002 MyAtari magazine