[abc80] Super Smartaid Cartridge

[H. Peter Anvin]

On 4/24/19 12:01 PM, Anders Sandahl wrote:
> Well,
> 
> For all curious people:
> https://www.abc80.net/archive/luxor/Prom/fw/super-smart-aid/
> 
> The 82s131 is dumped as well! It was a little project to unsolder the PROM
> but everything went well. No smartaid was injured during the process!
> 
> /Anders
> 

The 82S131 is definitely being used as an address decoder, and it looks
like only half of it (256 words) is actually used.  Without tracing the
wiring it is probably hard to know what the various values mean, though.

The data in the EPROMs makes no sense whatsoever. If I were to guess I
would say that the data and/or address lines are connected in a
nonstandard manner thus resulting in the dumped data getting scrambled.
 Just brute-forcing it would be ... difficult ... since there are 40,320
ways to permute the data lines and 6,227,020,800 to permute the address
lines on the 8K EPROM, for a total of 251,073,478,656,000 combinations.
 Since the data bus buffer sits on one side away from the rest of the
logic, I'm going to bravely assume that they didn't put in any kind of
intentional scrambling.

	-hpa