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View Full Version : Is Anybody Using The SD Systems Expandoram II With 4164 Chips For 256K On Board?



MicrocomputerSolutions
March 11th, 2016, 03:11 PM
I've been using a SD Systems Expandoram II since they came out in around 1980.

I've always used it as a 64K board utilizing 4116 dynamic rams. Recently I was looking at the technical manual available on S100 Computers and noticed that it talks about using 4164 ram chips to get 256K on the Expandoram II. There is a detailed list of modifications, and I'm playing with the idea of trying it, since I already have the 4164 chips, and would like to try running SDOS/CPM 3.0 in Banked Memory Mode with the SBC-200.

So, I'm looking for people who have a Expandoram II and are using 4164 memory chips to verify that this works, before cutting up my perfectly good Expandoram II.

spiette
December 25th, 2017, 09:39 AM
Did you ever move forward with this?

I've got a small pile of Expandoram II boards and I dimly remember doing this ages ago but can't find that board or the PROM for mapping it.

MicrocomputerSolutions
December 28th, 2017, 12:13 AM
No, I never modified my original Expandoram II board.

I was thinking that I'd buy another one, and experiment on it after getting it running, but never got that far.

spiette
January 11th, 2018, 10:27 PM
I'll update this if I get anywhere. I seem to have misplaced the tubes of 4164s downstairs. Can't remember when I last saw them, could be years or decades. :)

bcc
January 14th, 2018, 09:53 PM
What revision of the board was that mod for?
I do have a few of these and other SD Systems boards. They are on my list of to-do's for restoration. Some ended up as the base of mud dobber nests and will require at least a few sockets be replaced and a few corroded chip pins as well. I need to identify how many complete sets I have ( SBC-100, expandoram II revE, VDB-8024 and Versafloppy I). If I have an extra, will let you know. I see these often on eBay as well.

spiette
January 18th, 2018, 02:29 PM
The upgrade docs I have say it's for the Rev D boards but the earliest manual I have talks about jumpers for 4164's and it's for a rev B board. My rev A card has the jumpers used but I can't find the manual for it.

There are engineering changes for rev A, B, and C cards for general operation but there are more changes between them and the rev D & E cards. If you have a Expandoram II rev E could you take good pictures of it. Rev D is the last I have.

bcc
January 21st, 2018, 06:32 PM
The upgrade docs I have say it's for the Rev D boards but the earliest manual I have talks about jumpers for 4164's and it's for a rev B board. My rev A card has the jumpers used but I can't find the manual for it.

There are engineering changes for rev A, B, and C cards for general operation but there are more changes between them and the rev D & E cards. If you have a Expandoram II rev E could you take good pictures of it. Rev D is the last I have.
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Have you referenced the documentation on the S100computers dot com web site under S100 boards, SD Systems? They have a picture of a Rev E Expandoram II board and manuals of each revision (I, II and III) with schematics. Note the Update Manual for Rev II. Other than these technical bulletins in the Rev II update manual, I have seen no others on the web, but Rev III schematics may help.

spiette
January 25th, 2018, 10:34 AM
The ExpandoRAM I, II, and III are three different cards. There are revisions of each card and in this case we're talking about ExpandoRAM II board revision levels.

The picture I think you're referring to is a an ExpandoRAM I revision E which is an earlier/simpler design for 8k or 16k DRAMs.

I didn't look much at the ExpandoRAM III board since I remembered it being a IEEE696 board but I should have since the manual is a little more fleshed out along with the design.

I have revision A-D of the the ER2 but I'd love to see a revision E, if such was ever released, to match against the schematic and my rev D board to identify the last changes.