Re: VGC Chip

Henry wrote:

Since we're dealing with 20 year old IC's most basic analyzers will work just fine. Now we just need to wait about 7-10 years and pick one up one on eBay for cheap! Once that happens then most if not all the 'secrets' of the IIgs will be unlocked and anyone will be able to use the info. Sooner or later I'll probably start sending stuff off to be cracked anyway.


What you're referring to is a technique known as 'black box reverse engineering'. It involves, as you describe, hooking up test equipment to all inputs and outputs and attempting to derive the internal 'schematic' by analysing the outputs generated by a set of known inputs.

This is actually quite straightforward - for combinatorial logic. Once you introduce *states*, then complexity increases exponentially at least. And by 'states' I mean any sort of memory, such as explicit memory used in registers, scratch ram etc, or implicit, such as state variables in a state machine.

Of course, the job is easier when you know *what* the chip does, and have *some* documentation on how it works (register map, etc). But it is quite difficult to use this information effectively in an automated process.

I suspect you won't learn *anything* useful at all about the VGS with any sort of logic analyser that wouldn't be more readily apparent from studying the source code of a IIGS emulator.

The 'cracking services' are pretty high-end and AFAIK still involve some considerable human effort by experienced engineers. You have to have a good understanding of how common logic constructs are implemented at the chip level in order to recognise patterns and interpret the results. Way out of the realm of a hobbyist hacker, who may not even be capable of understanding or using the results!

If you were looking to mass-produce a clone with a market of 100K units then it may be worth your while. I also suspect the $4K starting price would be for a small support or security chip.

Regards,

--
Mark McDougall, Engineer
Virtual Logic Pty Ltd, <http://www.vl.com.au>
21-25 King St, Rockdale, 2216
Ph: +612-9599-3255 Fax: +612-9599-3266
.

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