Add RAM to 5170 motherboard?

[platatomi]

Is it possible to add more than 512KB of RAM to an AT motherboard? I know the RAM chips can be stacked in a PC, how about an AT?

If a second layer could be added, would that give me a full 1MB?

And if so, are the memory chips compatible between different AT motherboard versions? (looking to upgrade a third-version mobo, have a junk 1st version to rob parts from)

 

[modem7]

Is it possible to add more than 512KB of RAM to an AT motherboard?

Yes.
The first upgrade would be an expansion card that provides 128K beginning at the 512K mark, so that you end up with 640K of base RAM.
Beyond that would be the use of expansion card/s that provide extended RAM (RAM past the 1M mark).
IBM provided cards for the 5170 that to do that. They are shown at http://www.minuszerodegrees.net/5170/cards/5170_cards.htm
Of course, there were other companies that provided compatible cards.

I know the RAM chips can be stacked in a PC, how about an AT?

Where you see stacked (piggybacked) RAM chips, the chip on top is different to the chip underneath.

If a second layer could be added, would that give me a full 1MB?

No, you can't do that.

And if so, are the memory chips compatible between different AT motherboard versions? (looking to upgrade a third-version mobo, have a junk 1st version to rob parts from)

The type 1 motherboard requires 128Kbit chips, whereas the types 2 and 3 motherboards require 256Kbit chips.

You should have a read of the VcWiki page we have here for the IBM 5170. It contains lots of information.
http://www.vintage-computer.com/vcforum/showwiki.php?title=Systems:IBM+PC+AT+5170

Also, at my web site (http://www.minuszerodegrees.net) is other information on the 5170, including the IBM manuals.

 

[deathshadow]

I think modem 7 missed a detail; as you were asking about "to the motherboard"... in which case on a real 5170 board... no.

But as mentioned, that's what RAM cards are for... one of the best being the Intel Above Board... if you can find one.

 

[modem7]

I think modem 7 missed a detail;

Yep. Missed it by a mile.

 

[platatomi]

I have a couple of expansion cards, as AST Six Pack Plus and an EV138. Although these cards contain 384K and 512K of memory respectively, adding them to my 512K motherboard still only gives me 640K. Is there any way to use all the memory on these cards?

 

[modem7]

I have a couple of expansion cards, as AST Six Pack Plus and an EV138. Although these cards contain 384K and 512K of memory respectively, adding them to my 512K motherboard still only gives me 640K. Is there any way to use all the memory on these cards?

No. They provide conventional (base) RAM only.

Both models of the AST SixPakPlus are designed for the PC and XT, not the AT (info source: user manuals).
You may experience problems caused by possible incompatibility.

The EV138 is sure to be in the same boat.

RAM cards designed for the AT will have faster RAM chips, and be 16-bit, to provide comparable speed with the RAM on the motherboard.
eBay item 170737527935 is an example of a third party card for the AT that provides RAM from the 512K mark to the 640K mark.

 

[vwestlife]

There was also the Boca Research "TophAT", a small ISA card whose sole purpose was to expand an IBM AT from 512K to 640K.

 

[siliconsy]

An old thread I know but I have an tophAT ISA card if your still after one?