Re: eb164 63 MB limit?

Robert Allen Barker (
Tue, 12 Nov 1996 08:57:23 +0800 (SST)

> At 11:21 AM 11-11-96 -0800, you wrote:
> >Hi again,
> >
> > after weekend of experimenting
> <snip>
> >I read elsewhere on this list that this might be
> >related to the version of a particular eeprom on the mother
> >board. I thought U12 was mentioned. My U12 has a version number
> >of DAF2. The chip is a Xilinx 17128dpc.
> >
> >Does anybody have any definitive information regarding this?

Yes, we have had similar experiences to Maurice (below) and we also have the
DAF2 version serial rom. Our memory modules came without the small surface
mount resistors that set the PD code to tell a system how much memory is on
the module. In our system only memory slot 1 is read by the hardware so we
soldered resistors on that module. Only three of the 5 resistor positions
are related to memory size, the other two don't seem to matter, we
experimented with various combinations until MILO or the ARC reported the
correct memory size. We have used 64MB, 128MB, and 256MB configurations.

> Nothing definitive, but I have used boards with the U12 chip labelled the
> same, that is to say DAF12, and they sometimes worked, sometimes not. DEC
> sent me some replacements labelled "3EEF" that cured problem once. I
> received these replacements from Vince Yannett, E&RT Hardware Engineering,
> (508) 841-2920
> They also sent me a program that would purportedly rewrite these PROMs, but
> of course, with this PROM on the board the machine wouldn't successfully
> load the PROM. I understand that if I had the PD code on my RAM suitable for
> the older chip coding this might be made to work. Even having the right PD
> jumpering on only SIMM 1 and 5 is good enopugh, because they only read the
> first SIMM of each bank for PD codes.
> >
> >At least my machine is running now.
> >

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