"Frankenputer" - a computer made from parts, often from other, dead computers...

Here are two pix of my "TRSborne" computer, that I built in the very early 1980s. It is based on the TRS-80 Model I, level II - it even includes original Radio Shock ROMs, salvaged from a dead TRS-80!

The case is made of 1/4" acrylic - I had originally made a nice case of galvanized steel, but the floppy disks refused to work in it! I scratched my head and other (computer) parts, until I found the reason: The 5" monitor, saved from a trashed Motorola 6800 evaluation kit, generated a lot of magnetic noise, which the case conducted to the disk drives! So, I scrapped the tinplate, and had to use acrylic instead. The case has a hinge so the keybord flips up and becomes a cover.

The disk drives are a strange 3" breed (but the disks are sturdy, with an internal shutter - much better than the 3 1/2" disks that appeared at the same time) - you can see one of the 3" disks in front of the keyboard - which is an original Radio Shock spare board. Everything else is homebrew or salvaged from other computers.

The two 4" x 6" pieces of veroboard, onto which I wrapped/soldered all the electronics can be seen below the disk dirves. Thanks to an electronic wizard friend of mine, we shrunk the 60 or so ICs in the original TRS to only about 30 or so - thanks to higher integration of the 74 series TTL we used... And we used HUGE RAM chips: 64 Kbit in a single chip! I used 8 of them - had to map out 16 K, to allow for the 12K ROMs and the 4K memory map for the keyboard, I/O, printer and floppy controller...

In this top view, behind the drives you can see the green "Percom" floppy disk controller board. Originally, I had planned to use one 5" floppy drive - even had a drive installed, but changed to two 3" instead, and got some storage space for disks, to boot - pun intended.

The KGB-stamped aluminum shield prevents electronic & magnetic interference from the monitor - still a problem even in the plastic case.

To the right, the power circuitry - toroidal transformer, rectifier, chopper board, big filter caps (30.000 uF, still too little - the video jumps every time the disk drives step a track...) and room for the heavy (some 4 pounds) 12 V, 6 Ah, lead-acid gel battery...

I lugged this with me back & forth every weekend, going to Hango. Nice to have a computer at the summer place, too!

This unit was a small sensation among friends - and it even got featured in a Finnish computer magazine of those past, easy, days. I mean, you didn't get very far or very fast with only a 2 MHz clock... Today, my 2-year-old $ 4.800 (ouch!) G3 PowerBook is considered slow at 333 MHz.

But somehow, we all managed. And it's actually quite revealing to again use the "Electric Pencil" software (huge, requiring at least 16K RAM!) and note that you can actually boot the computer, write a letter and print it much faster on a TRS 80 at 2 MHz as you can do in MS Word on a superfast PPC or Pentium at around 850 MHz! Heck, that's microwave frequency already - has anybody nuked any CDs lately - in a computer, not oven, that is? ;-)

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