repairing early HP calcs

[woodelf]

Chris M wrote:

>I dont own any. But according to a recent Circuit
>Cellar article, early ics can be easy to implement in
>a FPGA. Dont have the issue in front of me, but the
>guy needed to mimic if you will a crt controller.
>Therefore could the chips used in the early HPs (maybe
>up to and including the 41 series?) be readily
>emulated by an FPGA?
>
>  
>
CPLD's are a better part as most FPGA's require pre-load from rom.
Still you need the original hardware and docs to create a FPGA design.
Some designers played often some nasty tricks with hardware.
I think for example in the TRS 80 /I  a 7400 with a defective unused
gate was used because it was cheaper than a working 7400.

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