Integral RAM upgrade
ard at p850ug1.demon.co.uk
Fri Feb 29 18:24:41 CST 2008
> > 7) If it works, set all the links as for a 1M board, trst again
> Which, of course, leads to the question : what are the linksettings
> for the 1M board ?
The Integral RAM expansion board seems to have been able to be popluated
with either 64K*1 or 256K*1 DRAMs, either 1 bank (16 chips) or 2 banks
(32 chips). All RAMs must be the same type. If 256K chips are fitted,
then U45 (74ALS157) is also fitted (to provide the extra address line to
the RAMs), it is not fitted on PCBs with 64K RAMs
The links have the following functions :
W1 : Bank select -> A17
W2 : Bank seelct grounded
W3 : Bank select -> A19
W4 : A17 not part of card select address
W5 : A18 ditto
W6 : A19 ditto
W7 : A17 is part of card select address
W8 : A18 ditto
W9 : A19 ditto
W10 : Connect CAS/ to RAMs if U45 not fitted (must be cut if U45 present)
W11 : Card ID vbit 2 = 1
W12 : ID bit 1 = 1
W13 : ID bit 0 = 1
W14 : ID bit 2 = 0
W15 : ID bit 1 = 0
W16 : ID bit 0 = 0
128K (Conjectured, I have no evidence that HP ever shipped this board) :
W2, W, W8, W9, W10, W11, W12, W16. 16 off 4164 RAMs.
256K (82925, taken from photo on hpmuseum.net)
W1, W4, W8, W9, W10, W11, W15, W13. 32 of 4164 RAMs
512K (82927. taken from the board I upgraded)
W2, W4, W5, W9, U45 (/ASL157), W11, W15, W16. 16 off 41256 RAMs
1M (82916, settings after I upgraded my 512K board)
W3, W4, W5, W6, U45 ('ALS157), W14, W12, W13. 32 off 41256 RAMs.
> Jos, busy finding the DRAM's in my "archive"
A it of advice if you're doing the upgrade. If, as I did, you decide to
socket the new RAMs, you can used turned-pin sockets, but it's tight.
It's based to put all 8 sockets of a row in position, then 'tack solder'
one pin of each socket to keep them in place, check they're all fitted
properly and solder the remaing pins. If you fit the sockets one at the
time you may have problems getting the last one in!.
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