Re: 8250LP - fault, how to fix?

From: Adrian Vickers (
Date: 2002-02-14 00:23:53

At 21:49 13/02/2002, you wrote:

>Adrian Vickers wrote:
>>Also, there are several "unique" chips on this 8250LP (i.e. which don't 
>>appear on the straight 8250). These are marked:
>>251166-01 (UV erasable eprom)
>>251165-01 (UV erasable eprom)
>>251167-01 (EEPROM? No UV window, but similar package to above two)
>>There's also one on the 6530 daughterboard marked 251474-01B (also EEPROM?).
>Sometimes Commodore has used several part numbers for essentially the same 
>chip.  An example is the Commodore 64 PLA: there are at least two 
>different part numbers for it, maybe three, although the logic is always 
>programmed in the same way.
>It would be very useful if you read the contents of those chips, so that 
>they can be archived on FUNET, just like all other Commodore firmware. You 
>don't necessarily need an EPROM burner for the task; all other ROMs except 
>the GCR table can be read out by software commands.

I would love to - but I haven't got the faintest idea how. Also, since the 
drive is totally unresponsive to computer commands (i.e. it hangs the 
computer until the drive is unplugged/switched off), I can't see any way of 
getting at them in software.

If anyone reading this is based in or near London, I'd be happy to loan the 
unit out for the purposes of getting images of these chips. Especially if 
they could have a stab at fixing it :)

Unlike the big 8250s, this block is potentially luggable on public 
transport, given a sufficiently strong plastic bag or three.

>If the main logic board is very similar to the high-profile 8250, you 
>could perhaps plug those chips in the equivalent sockets in the 8250. If 
>the 8250 boots up without problems, then you at least know that the 
>firmware is very similar if not identical, and that the problem is not in 
>the firmware.

Unfortunately, the boards are entirely different. Excluding the 'LPs 
daughterboard, there are the same number of what I assume are firmware 
chips (identified as 901887-01, 901888-01 and 091467-01), but I wouldn't 
like to try to swap them. They have a different number of pins, for 
starters... :)

>>Does anyone know what these are, and whether a failure in one of those 
>>might cause the zero page fault?
>I'd say that it is unlikely.  I assume that one of those three chips is 
>the GCR table ROM, and two of them are the $c000-$dfff and $e000-$ffff 
>firmware for the DOS CPU.

The 211165-01 and 211166-01 chips are together, so I guess they'd be 
$C000-$FFFF. Which means the GCR table is probably the 211167-01.

>  The fourth chip on the 6530 daughterboard could make the drive 
> controller CPU halt, which the DOS CPU could identify with that blinking 
> pattern.

I wonder, is it a kludge to make the 6530 behave differently? There's a 
tiddler chip next to it which might be a small amount of RAM, so 
conceivably the 251474-01B contains further firmware, maybe at a memory 
location below $C000?

Cheers, Ade.
Be where it's at, B-Racing!

Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (
Version: 6.0.314 / Virus Database: 175 - Release Date: 11/01/2002

       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail 2.1.1.