Simon Burge wrote:
> Hi folks,
>=20
> I went to upgrade my pc532 from 8x 1MB SIMMs to 4x 4MB SIMMs, and didn't
> get any joy.  From what I could tell from the schematics, I should
> jumper J1 to 1-2 connected for 4MB SIMMs (it's currently 2-3 with 1MB
> SIMMs).  I tried all four combinations of J1 & J2, before giving up and
> going back to 8MB total.  It may be bad RAM, or it could be just as
> simple as not having the right jumpers set up...

I think you just jumper both of them from 2-3 to 1-2. Do you have three
chip 4mb SIMMs? In that case you need to patch your hardware:

	From pcsbst.pcs.com!mips.com!daver!owner-pc532 Sat May 23 03:37:06 1992
	From: "Mark J. Munkacsy" <m2m@sgfb.ssd.ray.com>
	To: pc532@bungi.com
	Subject: Re: PC532 won't work with Samsung memory
	Date: Fri, 22 May 92 08:27:07 -0400
	Message-Id: <9205221227.AA27580@sgfb.ssd.ray.com>

	Here's the additional memory info I promised . . .
	    I'm using 1Mx9 Samsung KMM591000AN-8 SIMMs.  Although the data
	sheets shed no light on the subject, I determined through
	experimentation that they will not tolerate /WE activity during a
	refresh cycle; however, the pc532 DRAM controller allows /WE to change
	as soon as the CPU tries to begin a bus cycle, even if the DRAM is in
	the middle of a refresh cycle.	The symptom I observed is that
	following one of these "illegal" /WE refreshes, all DRAM read cycles
	generate different data than what was put in to the DRAM on a write
	cycle -- until a "normal" refresh (with no /WE activity) kicks the
	SIMM back to normal operation.
	    The "cure" is to gate /WE with /RFCYC.  This keeps /WE disabled
	during refresh cycles while permitting normal operation on normal bus
	cycles.
	    To do this I added a new IC, call it U99, in the spare slot next
	to U20 on the pc532 board.  A 74AS10 is perfect for U99.  U99 will
	perform the generation of /WE that is currently performed by part of
	U30.  I tried really hard not to make any cuts to the beautiful PCB,
	and by bending leads over on one of the ICs I was successful.  Here's
	what I did:

	    1. Disable U30-11,12,13 by bending these 3 leads over and
	reinserting U30 into its socket so that these leads are effectively
	not connected.	I know there are Good Reasons not to leave a gate
	floating, but it hasn't caused a problem [yet].
	    2. Jumper U99-7 to a convenient ground. U99-14 should already have
	Vcc present (thanks to George).  If you haven't already done so, give
	U99 a Vcc-to-ground bypass capacitor.
	    3. Jumper from U19-14 to U99-1  (/DDIN)
	    4. Jumper from U19-23 to U99-2  (/DDINL)
	    5. Jumper from U19-5  to U99-13 (/RFCYC)
	    6. Jumper from U18-9  to U99-12 (/WE)
	    7. Tie unused U99 inputs (pins 3,4,5,9, 10, and 11) to +V (e.g.,
	U26-1 or U31-1, or any other convenient point).

	    That's it!	I've had no problems at all running this at full speed
	(50MHz for U25).
	    I can't tell for sure if this is the problem that Stuart and
	Julian are having, but it sure sounds similar.	Good luck!
	-----------
	Mark J. Munkacsy, AJ1B	  m2m@sgfb.ssd.ray.com

> Unfortunately, I this info isn't in the pc532 FAQ on our webpages, and
> I can't find my 10-year-oldish pc532 booklet.  Is there anyone who
> can send me all the jumper (and I guess SIMM) configurations (for all
> jumpers, and not just the RAM setups) so I can add them to our FAQ?

I'll have a look at the stuff I have at home.

> Related to this, I believe it's simply a case of dropping in a 60MHz
> crystal in place of the 50MHz one to run your CPU at 30MHz, and a CPU
> fan is recommended.  Is this true?  I'll add some details of that to the
> FAQ as well...

My pc532 probably was the first to run at 30MHz and I just replaced the
crystal and put a i486 fan onto the CPU. At the moment it has an uptime
of 25 days. I'm running it in that configuration for at least the last
five years. You should specify "options CPU30MHZ" in your kernel
configuration.

Regards, Matthias
--=20
Matthias Pfaller                            Software Entwicklung
marco Systemanalyse und Entwicklung GmbH    Tel   +49 8131 5161-41
Hans-B=F6ckler-Str. 2, D 85221 Dachau         Fax   +49 8131 5161-66
http://www.marco.de/                        Email leo@marco.de