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How do I configure this 1MB RAM card by Lo-tech
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Posted on Monday, September 18th 2023 by Averagebadtechguy to r/vintagecomputing | 18 points
I recently bought the Lo-tech 1MB RAM Board rev.2 and i am confused on how to read the dipswitch settings to set the ram amount. I intend to place it int oan ibm 5160 and it currecntly has 256KB of ram and want the max amount. Does anyone know how to set it?
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@ Tuesday, September 19th 2023 by Ice_BergSlim | 1 point | Reply
It would be nice to see the bank of switches and the capacity of the ram card itself.
@ Tuesday, September 19th 2023 by Averagebadtechguy (OP) | 1 point | Reply
I couldnt send that photo but I have the original listing to look at the data and images.
https://www.ebay.com/itm/285405268591...
@ Tuesday, September 19th 2023 by maddogg42 | 1 point | Reply
At a glance it looks as it lets you set the switches to reflect the amount of ram you need. 1024 bytes is 1 megabyte, so if you want the "max ram" on this card then you would set the switch to 2.7
@ Tuesday, September 19th 2023 by Averagebadtechguy (OP) | 1 point | Reply
I would like 384kb of ram as I learned the max my 5160 can handle is 640kb. Also i dont know how to set switches to 2.7
@ Tuesday, September 19th 2023 by gcc-O2 | 2 points | Reply
Most of this card's memory above 640K is not going to be usable. D000 and E000 should be free. C000 it depends whether you have an EGA/VGA video card or CGA/MDA. A000 and B000 should be taken up by video RAM but again it depends on the type of video card. And none of this memory above 640K will be used by DOS without a UMB provider like USE!UMBS.
@ Tuesday, September 19th 2023 by pmodizzle | 6 points | Reply
You see how there are two switch blocks on the front of the card? Each one corresponds to each column on the back of the card.
example: you said you want 384k from this card to add to your 256K on the board to get 640K:
Switch block 1 should have switches 1-6 in the on position. All other switches on block 1 and 2 should be off.
@ Tuesday, September 19th 2023 by Averagebadtechguy (OP) | 2 points | Reply
thank you
@ Tuesday, September 19th 2023 by Averagebadtechguy (OP) | 2 points | Reply
i just tried this and for some reason my ibm now just counts to 384
@ Tuesday, September 19th 2023 by pmodizzle | 7 points | Reply
Sorry that was my bad I wasn't thinking.
You need to leave the first 256K "off" to allow your computer's ram to have that place. Then open the switches on your card to the 640K limit (Switch bank 2.2).
1.5 to 2.2 should be "on". All others "off"
@ Tuesday, September 19th 2023 by Averagebadtechguy (OP) | 3 points | Reply
thank you
@ Tuesday, September 19th 2023 by Knowcrap | 2 points | Reply
Try reversing. Reading the manual, I believe each dipswitch that is on will enable that page. Ex. You want to start at 256, so leave 1.1 through 1.4 off and turn the rest on. Or at least 1.5 through 2.2 are on.
This is what their wiki says:
The board is configured via two banks of DIP switches, which control whether each physical segment (=64KB) is active on the memory board.
So I'm guessing that's what it means.
You likely won't kill anything, so maybe experiment with it. Like all off except 1.5 and note the behavior. Then turn on 1.6 and so on.
@ Tuesday, September 19th 2023 by Ice_BergSlim | 1 point | Reply
try 1-4 on on switch 1 and 1-2 on on switch 2
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