[s-cars] ECU specs anyone?

[Dave Ellis]

I'm hoping someone on this list has the operating specs for the factory 
ECU EPROMs.

For my own information I decided I might toy around with the ECU code 
and see what I can learn.  I have no real intention of changing 
anything in the code (which could be BAD(tm) if done incorrectly), and 
have already decided to purchase one of Mihnea's programs once all the 
other more pressing mechanical issues are sorted.  I'd just like to see 
what's going on in there and for now to read out the EPROM code to play 
with on my workstation, and make a backup set of EPROMs while I'm at 
it.

So far I've learned the following:

Form Factor: 28 pin DIP TOP EPROM or EEPROM
Socketing Form Factor: 28 pin 600mil DIL
Fuel and timing control IC is a 27c512 (64k x 8)
Boost control IC is an 87c257 (layout?)

Does anyone know the following for our S-cars?:
  -recommended thermal operating range required?
  -operating speed tolerances (somewhere between 35ns - 170ns)?
  -operating voltage tolerance?
  -layout for the 87c257 IC?

I've been looking at data sheets trying to find a supplier that offers 
the correct EPROMs in a package designed for automotive tolerances.  Do 
any listers who've worked with the EPROMs happen to have any favorite 
brand/models they've had good success with?  Any to avoid?

I haven't pulled my ECU yet, but may do that next weekend and solder in 
a couple of sockets if needed.  I understand that on some of the 
earlier S-cars the ECU boards came pre-socketed rather than soldered, 
does anyone have any details about that?

Thanks for your help!

-Dave
'93 S4
'99.5 A4 1.8t