Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!mcsun!hp4nl!telmail!neabbs!joost
From: joost@neabbs.UUCP (JOOST BOERHOUT)
Newsgroups: comp.sys.amiga.hardware
Subject: RE: FRANCES problems
Message-ID: <528208@neabbs.UUCP>
Date: 5 Jan 91 16:14:35 GMT
Organization: NEABBS multi-line BBS +31-20-5733533 (13x), Amsterdam, Holland.
Lines: 41

In message 526139 News.Amigahard, 04-01-91 10:55:07  Rob Hounsell wrote: 

>  I've got an Amiga 1000 that I've upgraded using the LUCAS accelerator and
>the FRANCES 32-bit memory expander with 1 Meg installed. The memory tests out
>fine using the diagnostics that came with the FRANCES board, but when I add the
>memory to the system (i.e. it doesn't autoconfigure) the system recognizes the
>extra ram, but locks up within 1-5 minutes. 
>
>  Before it locks up, if I insert a disk, I often get a system requestor with a
>message like:
>
>   Validation Error
>   Key 880 checksum error
>
>  This key value of 880 is very consistent. What is it telling me, and what
>could cause this problem just by adding extra memory (i.e. why key 880??).

Hmmm, sounds like power line noise. The problem is that testing the memory
using the software tool supplied with FRANCES is NOT sufficient. If there
is anything actually running in FRANCES memory (e.g. exec) there is a lot
more power line noise due to more (/different) access cycles to the board.
This will happen the moment you tell exec to use FRANCES. A side effect of
this is that in some cases disk access is not possible (i.e. Exec reads
garbage from the drive and concludes it's a bad disk).

Normally one should not notice these noise problems of course. However, the
A1000 and FRANCES have noisy busses. An important thing to battle noise is 
to use MULTILAYER CERAMIC capasitors only.
Use a multimeter to check ground/power line voltage differences. Check the
gnd/pwr terminals of the LS245 chips on FRANCES. If the meter reads more
than 10mV run a wire to the expansion bus (or piggy back board).

>unless the system recognizes the extra memory. I'm sure I've got a short or a
>loose connection somewhere, but it would help to know where to look.

No I don't think it's a short. (PS: have you tried a 74HC74 for U9 ??, it
may sound strange but it's the ONLY chip which works in my system.)

>Thanks,
>Rob

- joost -