Creating ROM chips

[psyolent]

Hey

So this is WAY off topic from automotive, but computer related. Mr Eccentric is at it again.

I have a love for all things old (Commodore computer / c64/128, Amiga etc) - these machines had proprietary ROM chips in them for different purposes graphics, IO, etc etc.

These are no longer available - sure theres some NOS buried away but alot of 'newer' machines are made up components pulled from old machines.

How hard would it be to re-create these ROMs? How could you re-create the logic the ROM has inside it and write it to something newer? Or is there something so specific in the ROM which may make it not feasible ?

[antus]

Well theyre not rom - read only memory - they're particular circuits with particular functions. Essentially you'd need to reverse engineer anything where official docs dont exist (pretty much done, the emulators have software implementations) and then engineer electrically compatible ICs in the same physical package. Doable? Yes. Worth it? Probably not ahead of other options.

[psyolent]

thanks antus for clarifying. they were called ROMs, gary, paula, denise, agnus, fat agnus and obese agnus. i should probably study engineering of some descript but alas i am old and it would take years for me to catch up with a level of experience required to be actually useful.

the emulators though get the functions wrong sometimes.
so the emulation is 'pretty' good, but not completely right = slight flaws in the reverse engineering OR the code to support same (in software) is not quite right.

what other options would be worthwhile antus? to reverse engineer the existing chips - how do you extract the logic from the chip? i know with something i'm collecting bits for there are a set of 'jed' files for minor ICs on the board which need to be programmed, however the real custard is in the custom ICs that are harvested from old c64's/amigas etc. it just seems a waste to destroy old hardware for something which could be re-created in a similar package with or without adapter....

[antus]

How deep are your pockets? There are companies that do it for fee but its out of reach for normal people. Its essentially done by striping back the chip layer by layer both physically and chemically, and usong high power microscopes to peer in and software like this http://www.degate.org/ to convert to something usable. Thats digital but of that era I imagine its likely there is analog stuff there too.

Some of the newer emulators are accurate, and fixing them or using them as a base to reconstruct a new implementation would save heaps of time and money.

[antus]

See these guys, serious business... But they often find some interesting stuff in there! http://www.chipworks.com/about-chipwork ... ense-humor

[psyolent]

it seems that way. they have to be VERY deep. yeah i was just reading chipworks LOL. that said it seems like its already being done antus

http://amiga-dev.wikidot.com/information:hardware

[ralcool]

http://blog.tynemouthsoftware.co.uk/201 ... eview.html

I came across this a few months ago, it might go towards helping your quest. I thought it rather clever.

I used to hang out heaps on an Atari ST forum and went to some length to learn its secrets, and create hardware for it.

Alas, Anything that you might create tends to be for a limited market. A bit like this forum really, but no less interesting.

We do it for the love of the machine.

[j_ds_au]

Well, the name Fat Agnus rings a bell, because the name is, well, memorable (no pun intended).

However, as Antus said, these are not ROM's. What they are, are ASIC's. A much more exotic and specialized animal. The only thing that might, with a very deep pocket, be able to emulate such a beastie, is an FPGA/CPLD, or perhaps in some unlikely cases, a high speed MCU. Serious amount of engineering work, including the reverse kind, would be required.

Joe.

[vlad01]

Yeah I would say PGA might be the way but you need to know the original logic.

[psyolent]

nailed it ralcool. this is exactly where i was heading :

but a similiar size of device to replicate the custom ASICs (thanks joe)

yep. fat agnus, agnus, obese agnus (8375A, 2MB chip)

i wonder if the original logic is out there or captured in patents somewhere?

or could you 'stack' the original chip, with something like that picture in the middle to capture all operations , then, run the machine and capture? does that make sense?
as you've likely deduced i know little to nothing about electronics other than how to solder