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Z-RAM-3D ST ram upgrade module.


Veteran Member
Sep 28, 2012
Indiana, USA
Hi all, I bought a pig in a poke on eBay the other day. It's a RAM upgrade board that was removed form a "working" ST. It's called a "Z-RAM-3d/4Meg." by a company called Zubair Interfaces Inc. There was no documentation with this item, but I also bought the motherboard the upgrade was originally installed on. The motherboard had been scrapped out. The socketed chips were removed and the RAM looks like it was removed with a chisel, but the attachment points for the ram upgrade were visible. The problem is there are more connections coming from the upgrade module than there are attachment points on the motherboard.

So my hope is that someone here has, or has documentation, or really any information on this ram upgrade.


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Veteran Member
May 23, 2009
From an old sales GENIE sales catalog:

Z-RAM 3-D/4Meg Zubair Interfaces (213)408-6715 105.00

Z-RAM is the universal, reliable and compact 2.5 to 4Mb upgrade in 1
kit for 520ST, 520STfm, 1040ST, Mega ST 2 computers. You can use 16 x
1Mb RAM chips to upgrade to 2.5MB and add another 16 to upgrade to 4MB
total. Z-RAM is two boards each holding 2MB soldered together with a 40
pin socket going through them. A pingrid board is cabled to the main
boards. The pingrid board piggybacks over the MMU chip. Z-RAM will work
with 1MB chips 120ns or less, even 150ns speed. (Solderless).

I think the person who disassembled it destroyed it. The pictures I have seen show the cables running into a pass through socket that would plug into a motherboard socket to tie the new memory into the system.