From: Adam Quantrill (aquantrill_at_scigen.co.uk)
Date: Wed Apr 07 1999 - 09:37:34 EDT
If by that you mean http://www.pc.ibm.com:80/cgi-bin/bookmgr/BOOKS/tpvol2/5.0
then I've had a look and there are no pcb layout diagrams identifying the memory chips.
Let me know any other URLs to look under, if there is more info out there, thanks,
- Adam
______________________________ Reply Separator _________________________________
Subject: Re: [755C] Memory parity problem - some success
Author: MIME:Bill Morrow <penzance_at_icanect.net> at INTERNET
Date: 07/04/99 13:23
take a look at the hardware manuals on the IBM site.. i've seen memory maps, though not chip placements..
i have that address on another machine, busy this morning, gotta run, if you can't find it, let me know.. :-)
Adam Quantrill wrote:
> I got the data sheets on the chips and my assumption was correct - each is 512k*9bits. I have lifted the power supply pins on a number of the chips and got '1668KB OK' so I then added the expansion ram and that quite happily sits on top o
the new memory boundary. I'm not sure that I have disconnected the chip that was giving gyp (!) but it now all works albeit with slightly reduced memory. >
> The question still stands, however, what is the arrangement of memory chips in the memory map? I reckon on there being 16 bit words so I have to disconnect maximum 2 chips, leaving me with 3MB on the motherboard. However if the bus were 3
bits wide I'd have to disconnect 4 chips. But the question is which 2/which 4? I've disconnected a few chips at a time but there doesn't seem to be an unambiguous logical relationship (so far) between which chip/what memory you get.
>
> Anyone with any clues as to the placing of the memory chips on this motherboard?
>
> - Adam
>
> ______________________________ Reply Separator _________________________________
> Subject: [755C] Memory parity problem on motherboard
> Author: MIME:Adam Quantrill <aquantrill_at_scigen.co.uk> at INTERNET > Date: 30/03/99 09:54
>
> I've disassembled my 755C and there are no obvious cracks or bad soldering on what I take to be the RAM chips (HM514900ALTT7R) but nevertheless I intend to reflow them just in case. Does anyone know the correspondence of memory location t
chip? As there are 8 of them I assume it's one chip per half megabyte, each being 9 bits wide as you can have parity. I'd rather reflow and/or replace just the duff chip, and as the error is at 3.7MB it will be the last one. >
> Any advice in this area would be appreciated. >
> - Adam
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