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IBM 5170 512kb board ram upgrade?

robbo007

Experienced Member
Joined
Jan 7, 2012
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287
Location
Iberian Peninsula
Hi guys,
Is it possible to upgrade the onboard ram on the IBM 5170 512kb board to 640kb? At present I have a 128KB ISA card filling the rest of the base memory but need a spare ISA slot.
Thanks,
 
I am unaware of any published instructions. If any, there would be one set of instructions for the type 1 motherboard, and a different set of instructions for the type 2 and type 3 motherboards. It's not as simple as changing RAM chip type. For example a motherboard modification would need to be done so that the motherboard decodes the 512K to 640K address space.
 
There are boards which provide both the 512k-640k "conventional" memory, as well as expanded and/or extended memory, as well as boards which do those things plus provide serial and parallel ports (the Intel AboveBoard Plus I/O, for example). Perhaps you could gain a slot or two by consolidating.
 
ok great thanks for the points. Yeah I think my only way will be a multi board that has the additional base ram on it. Many thanks.
 
It probably wouldn't be possible to modify type 2 or 3 boards for 640kb, because there is only one bank of memory, and it already has the 256kb chips fitted.
It might be possible to coax a type 1 board to accept 256kb chips, but no hobbyist has ever done it as far as I know. I think it would be pretty cool to have 1MB on the board.
Supposedly there were 10MHz AT prototypes using type 1 motherboards that had been modified to take 640kb, but the former IBM employee who had them is now deceased.
 
So I found a Quadram-Quadboard which could be a candidate. A couple of things, it's got a battery on it for the RTC. I gather these can be replaced? My AT has a external battery pack for the RTC. Will this conflict? Can the RAM on these boards be used as "base" memory to fill my 512kb to 640kb or is this expanded/extended RAM?

Thanks.
 
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