Re: 8250LP - fault, how to fix?

From: Nicolas Welte (
Date: 2002-02-14 10:25:34

Adrian Vickers wrote:
> 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... :)

There are two different versions of the 8250LP mainboard: One takes the usual
24pin ROMs from the 8250, the other one has 28pin sockets for 2564 EPROMs. I
tried to put ROMs into the EPROM sockets, it doesn't work. The EPROMs should
contain the same code, but I never checked it. I hope I still have a drive at
home with EPROMs installed.

> 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?

The 6530 contains ROM, RAM, I/O and timer. Somehow Commodore didn't want to
make a new 6530 versions with a ROM for the SFD1001 and 8250LP, so they used
adaptor boards that disable the ROM in the 6530 and replace it with the
contents of a 2716 or 2732 EPROM. But IIRC, only 1kB is used and mapped in
(at $FC00).

You can safely replace the 6530 on the adaptor board with the 6530 from the
8250, or you can even replace the whole adaptor board with a 6530. The latter
is only useful to diagnose problems with the adaptor board itself, the
internal ROM of the 6530 will probably not allow you to control the drive
mech. But the blinking code should go away. Oh, the 6530s are not labeled
6530, they contain a long Commodore part number. It's the only 40pin chip
with such a number :-)


       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail 2.1.1.