Integral RAM upgrade

Tony Duell ard at p850ug1.demon.co.uk
Thu Feb 28 13:51:10 CST 2008


I recently bought another HP Integral on E-bay, and after the normal 
cleanup on the floppy drive it works fine. The expansion slots both 
cotnained boards, one was a 512K RAM board, the other an RS232 oard 
(which is the main reason I watned this machine!).

Anyway, the RAM board was clearly identical to the 1M board, just with 
only have the RAM chips fitted and the links set differently. Having got 
a lot of 41256 chips on old PC memory boards, I spent the afternoon 
upgrading it to 1M.

BAsically :

1) Remove the bracket and cover from the PCB (torx screws)

2) Clean out the holes fro the RAM and their decoupling capacitors using 
a soldering iron and solder sucker. Test the board at this point, if it 
doesn't work, find the solder bridge between traces in the RAM area...

3) Fit 16 off 16 pin turned-pin sockets to the RAM space. Test again

4) Fit 16 off 0.1uF capacitors. I found the exact part at Farnell. 
They've been discontinued (They're not lead-free...) but they still had 
stock. Test again

5) Plug in the RAMs and test again

6) Removce the link 'W2' on the board (this is the bank select line to 
the RAM controller), link the end that's common with W1 and W3 to +5V 
(e.g. the end of the decoupling capacitor right next to that point). Test 
again. You're now using the new RAM chips only, as a 512K oard.

7) If it works, set all the links as for a 1M board, trst again

8) Finally put the cover and bracket back on.

Now for the curiousity. One one of the standard disks supplied with the 
Inegral is a program called 'status'. And one of the things it displays 
is the amount of free memory.

In my machine, wioth no RAM boards fitted. there's 264K free. With the 
512K board, it reports 764K free. And with the 1M board, 1264K free.

My question is what's happening to the other 12K of each half-meg? Or 
deos 'status' have an odd definition of a kilobyte?

-tony




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