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Question on 286 memory

timmcross

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Jul 12, 2021
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I have a Packard Bell IS/VT286 motherboard. It came with 2 banks of 41256s soldered on board and 2 banks of 4164s (640k conventional). I replaced the 4164s with 41256s and now the RAM shows up as 512k conventional and 512k extended.

Any way to switch the ratio to get 640k conventional again? Think I will have trouble with DOS programs needing more than 512k of RAM. I am still getting used to 286 memory maps. I have a Laser 286 where I can change the amount of conventional memory.

Link to system board info: https://stason.org/TULARC/pc/motherboards/P/PACKARD-BELL-286-IS-VT286-VERSION-1.html
 
The Leading Edge Model D2 (10 MHz) also works this way. It can't be changed. I wouldn't hold my breath the Packard Bell is any different in that regard.
 
Some systems had the option of splitting 1024KB into 640K conventional and 384 extended. The system had to support the option. Maybe the SETUP disk for the system would permit that? I had a 10 MHz 286 with Phoenix BIOS that could do the 640/384 split.

Otherwise, you either need to drop back to the original memory configuration or find an AT memory card. There were special 128K cards that filled the 512K to 640K area and some extended memory cards would backfill the 128K and then start the extra extended memory past the 512K of extended on the motherboard.
 
Your 512 + 512 is still better than the old NCR I had, it didn’t support any remapping

Came with 1mb of ram but only 640k was addressable, the rest was upper memory blocks :(
 
Ah, ok. Good to know. Would switching to another BIOS help or is that hardwired into the system board? Perhaps the Quadtel one on -0degrees.net?
 
Ah, ok. Good to know. Would switching to another BIOS help or is that hardwired into the system board? Perhaps the Quadtel one on -0degrees.net?
A bios might add more functionality but usually how memory maps is based on the chipset and memory controller on the board, the bios just knows how much is there.


According to this you need to change a jumper for 640k + 384


It was a big deal when the neat chipsets with better memory management came out for a reason.

Also worth noting, in some rare circumstances your board might take high density dips (1m) without spelling out support, I upgraded an old Futura 100 Pc this way but it had 4 bit dipps instead of the single bit chips. (And no parity)
 
Actually, that article mentions and older version of the board which is the one I believe I have. Seems like the older one doesn't support the memory config I am looking for.
 
Actually, that article mentions and older version of the board which is the one I believe I have. Seems like the older one doesn't support the memory config I am looking for.
Yep then you need to buy a 128k AT memory upgrade or an isa memory expansion device. A few folks here claim to have dumpster loads full of 128k At upgrade cards, might reach out here for one.

If you don’t mind the 512-640k area and the hma/upper blocks being glacially slow you could even use a lowtec 1mb XT board, did I mention slow?


Sort of unfortunate lotec doesn’t make their ram card in 8 bit and 16 bit versions. It’s not like 16mb of cache is very expensive now.

A combo lotec card with both ram, 16 bit IDE, CF and rom all together would be useful for those of us with a severely limited system (many Tandy’s only have one slot), keep it physically small and those with gimped luggables would make good use of it.
 
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