kentd@FtCollins.NCR.com (Kent.Dalton) (11/08/90)
Hi All,
Since a lot of netters seem interested in RAM upgrades, I thought I'd
share my RAM upgrade horror stories with you all (as well as a plea for
advice/comments). If you're an accomplished ST technician/ hardware hacker
please share some insight with me on this one.
Here's the deal- Machine: 520STfm, Board: Zubair Z-RAM
First, I get the board, plug 2Mb of 80nS DRAMs into it, and do the
installation, pretty easy, so far. I boot the machine and notice that as it
comes up when the disk drives are active the screen gets darker, but no
big deal. I run both of the supplied RAM tests and it passes without a hitch.
I'm the proud owner of a 2.5Mb machine. Wrong. After having the thing
installed for a while my disk files start to mysteriously become corrupted.
Everytime I write something to disk there's a 50% chance that the file I
just wrote has been munged. Looking at an ASCII file reveals many of the
characters have been incremented by one- i.e. a space turns into a !, a *
turns into a +, etc. I check the board for shorts, opens, good connections,
etc. Everything looks OK.
So, I call up Zubair with the above story, it sounds like he's seen this
problem before. He asks what brand of RAM I'm using.
"OKI", I say.
"There's the problem", he says, "get some low drain DRAMs, like Samsung."
He cheerfully sells me 2Mb of 80nS Samsung chips. I put them in my machine
expecting all my troubles to disappear. Nope. Now the thing won't even pass
the memory tests. Using one of my OKI chips, I check all the Samsungs to make
sure one of them isn't bad. Nope, that's not it.
I call Zubair again: "Try shortening the cable between the MMU and the
board". I do this. The board now passes all tests. Great, the ordeal is
over. Wrong again. After a couple of minutes of C programming my text
files are being trashed again (in exactly the same way they were w/ the OKI
chips!)
Yet another call to Zubair... this time they can't come up with any useful
suggestions.
What I now have: 4Mb of DRAM, a pcboard, a 512K ST, A lot less money :^{
So, if anyone has suggestions on what can be done, what the problem may
be, etc., I'd love to hear them. The only other symptom aside from the
disk drive's inability to write are "lines" of pixels that are darker
than the others running vertically up and down the mono screen. My current
theory is that my power supply is too weak... but I'm not going to try a new
one until I can determine if this is truly the problem.
--
/**************************************************************************/
/* Kent Dalton * EMail: Kent.Dalton@FtCollins.NCR.COM */
/* NCR Microelectronics * CIS: 72320,3306 */
/* 2001 Danfield Ct. MS470A * */
/* Fort Collins, Colorado 80525 * "This mind intentionally left blank" */
/* (303)223-5100 X-319 * All standard disclaimers apply */
/**************************************************************************/domen@hutch.crin.fr (Eric Domenjoud) (11/12/90)
Your problem makes me think of the one I currently have with my computer. Some time ago, it also started to corrupt my files, and I finally noticed that the bit 6 of odd (or was it even) adresses was systematically turned to 1. Perhaps you have the same problem with bit 0. My probelm is not related with a memory upgrade: it happened by itself. Unfortunately, I still not have my computer back, so I can't say you what the trouble is. Eric Domenjoud
ljdickey@aftermath.waterloo.edu (L.J.Dickey) (11/14/90)
In article <DOMEN.90Nov12101929@hutch.crin.fr> domen@hutch.crin.fr (Eric Domenjoud) writes: >Your problem makes me think of the one I currently have with my >computer. And it reminds me of the problems one of the fellows here in my town had. He tried two different places before he found someone who succeeded in installing his ram expansion. The first guy just failed. The second had to put in three different boards before he found one that worked.