Re: 8250LP - fault, how to fix?

From: Marko Mäkelä (
Date: 2002-02-13 22:49:01

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 

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.

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.

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


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