Building RAM Expansions For The DEC Rainbow 100

Building RAM Expansions For The DEC Rainbow 100

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It’s hard enough to get your hands on a forgotten computer from yesteryear. It’s even more difficult to get accessories like RAM expansions and graphics cards, because half the time they’re just discarded as random e-waste when they’re outside of their original context. [na103] has solved this problem for the DEC Rainbow 100 to a degree, by building new RAM expansions and graphics cards from scratch.

In the case of the RAM expansion, the design [na103] built is capable of boosting a Rainbow 100 computer to a full 896KB. This is more than other contemporary IBM machines like the 8088 XT, which had an architecture-enforced limit of 640 KB.  It was rebuilt from some notes and original DEC schematics.

The GS2 graphics card was recreated in a similar fashion, also relying on some photos snagged from the internet. Its GALs and PROMs are programmed using rips from an original board. While the design is considered complete, [na103] hasn’t yet had the opportunity to build and test it yet.

The trick is, armed with the right documentation, it’s not actually that impossible to recreate old hardware yourself. If you’ve been whipping up something similar in your own workshop, don’t hesitate to drop us a line!

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