pfales@ttrde.UUCP (Peter Fales) (12/16/88)
Here's one for you hardware experts. I have been trying to upgrade my 3B1 from 1MB on the system board to 2MB. I have a copy of the schematics and I thought it would be fairly easy. I have done the following. 1) Installed 4 Motorala 74F258 Multiplexers 2) Installed 36 Sockets, and 256KB DRAMS 3) Installed 27 0.1 uF bypass capacitors 4) Installed 16 33 ohm resistors (rather than the resistors packs, the parts were backordered and I was impatient) The system now boots and runs fine, but it doesn't recognize the extra memory. Is there anything more I have to do? Assuming I have done all that is required, how can I go about testing the thing? As far as I can tell, the diagnostic disk can not test any memory not recognized at boot time. As they say, thanks in advance, -- Peter Fales AT&T, Room 2F-217 200 Park Plaza UUCP: ...att!ttrde!pfales Naperville, IL 60566 Domain: pfales@ttrde.att.com work: (312) 416-5357
mvadh@cbnews.ATT.COM (andrew.d.hay) (12/16/88)
In article <803@ttrde.UUCP> pfales@ttrde.UUCP (Peter Fales) writes: >Here's one for you hardware experts. I have been trying to upgrade my 3B1 >from 1MB on the system board to 2MB. [] >The system now boots and runs fine, but it doesn't recognize the extra >memory. Is there anything more I have to do? Assuming I have done >all that is required, how can I go about testing the thing? As far >as I can tell, the diagnostic disk can not test any memory not >recognized at boot time. i did this last summer, with the same results. as far as i can tell, it looks like the motherboard needs some jumper wires added to steer signals to their new destinations. i haven't had time to try to match the schematics (which don't seem to correspond with the latest motherboard revisions) to my computer. i did try switching the 64k-256k chip jumper, and my machine dropped to 512k ram. we have 2Mb 3b1s at work, and i've gotten a good look at the 2Mb motherboard, without enlightenment, though i didn't have my motherboard side-by-side for comparison. btw, it looks (from the schematics) like you could piggyback the second 2mb on top of the first without much wiring. piggyback sockets needed, of course (anyone still make them?). >As they say, thanks in advance, Ditto (i mean, 'ditto', not 'Ditto', mike) -- Andrew Hay +------------------------------------------------------+ Holistic Specialist | I will design a computer for you, so powerful that | AT&T-BL Ward Hill MA | organic life will form part of its operational matrix| mvuxq.att.com!adh +------------------------------------------------------+
mike@mfgfoc.uucp (Mike Thompson) (12/17/88)
From article <2653@cbnews.ATT.COM>, by mvadh@cbnews.ATT.COM (andrew.d.hay): > > btw, it looks (from the schematics) like you could piggyback the > second 2mb on top of the first without much wiring. > piggyback sockets needed, of course (anyone still make them?). > > -- > Andrew Hay +------------------------------------------------------+ > Holistic Specialist | I will design a computer for you, so powerful that | > AT&T-BL Ward Hill MA | organic life will form part of its operational matrix| > mvuxq.att.com!adh +------------------------------------------------------+ I have been thinking the same thing, but I don't have schematics to fill in the details. A long time ago, I piggy backed 16k RAM chips ( it was a very long time ago :-) to bring a 16k TRS-80 color computer to 32k. Of course I had to redirect an address line to each chip with a jumper, but would a simular technique work to bring a 2MB 3B1 to 4MB. If anyone has done this before with a 3B1, I am sure the rest of us would like to hear about this. Mike Thompson --------------------------------------------------------------------------- Michael P. Thompson FOCUS Semiconductor Systems, Inc. net: (sun!daver!mfgfoc!mike) 570 Maude Court att: (408) 738-0600 ext 370 Sunnyvale, CA 94086 USA ---------------------------------------------------------------------------