ilan343@violet.berkeley.edu (02/12/90)
How many of the 386/AT motherboards out there are able to assign the top 384K of the first 1M as exTENded memory? This question was discussed a while ago in this news group, but I don't remember seeing a definite answer. I know the DTK/386 20Mhz motherboard (with a DTK BIOS) can do it. However, I haven't seen any other motherboards used by low-end clone makers that claim this capability. If you believe the sales people in the stores I went, once you disable the ROM shadowing in their machines those memory locations (the top 384K) are lost. Why is the DTK machine different? Motherboard, BIOS, memory configuration?
cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn) (02/12/90)
In article <1990Feb11.191736.7917@agate.berkeley.edu> ilan343@violet.berkeley.edu writes:
$How many of the 386/AT motherboards out there are able to assign the
$top 384K of the first 1M as exTENded memory?
$I know the DTK/386 20Mhz motherboard (with a DTK BIOS) can do it.
$However, I haven't seen any other motherboards used by low-end clone
$makers that claim this capability. If you believe the sales people in
$the stores I went, once you disable the ROM shadowing in their machines
$those memory locations (the top 384K) are lost.
The Suntac AT motherboard does this, too. You can select any memory
above 640K to be either extended or expanded ... it has no shadowing
option (at least, not the motherboard I have, which I bought about a
year and a half ago).
A friend of mine has a couple of ATs (I don't know what brand their
motherboards are) which are also capable of using memory above 640K
as extended memory.
--
Stephen M. Dunn cs4g6ag@maccs.dcss.mcmaster.ca
<std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
****************************************************************************
I Think I'm Going Bald - Caress of Steel, Rushdhinds@portia.Stanford.EDU (David Hinds) (02/12/90)
In article <1990Feb11.191736.7917@agate.berkeley.edu>, ilan343@violet.berkeley.edu writes: > How many of the 386/AT motherboards out there are able to assign the > top 384K of the first 1M as exTENded memory? My Mylex MXS386 board, with an Intel/Zymos chipset and a Phoenix BIOS, reclaims all the >640K memory that isn't used for shadowing ROM's. > Why is the DTK machine different? Motherboard, BIOS, memory > configuration? I think it depends mostly on the support chipset, which is responsible for remapping the RAM addresses to not conflict with everything else that goes above 640K. Incidentally, I've found that it is best to disable any kind of "hardware" ROM shadowing, and use QEMM to do it. For my board, shadowing can be switched on only for 128K blocks. With the Phoenix bios, only the top 32K is needed after booting - the 32K below that is only setup code. So, using QEMM saves 96K of RAM, and lets me remap other things into that space. -David Hinds dhinds@popserver.stanford.edu
tjr@cbnewsc.ATT.COM (thomas.j.roberts) (02/14/90)
From article <25D61BEE.29984@maccs.dcss.mcmaster.ca>, by cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn): > In article <1990Feb11.191736.7917@agate.berkeley.edu> ilan343@violet.berkeley.edu writes: > $How many of the 386/AT motherboards out there are able to assign the > $top 384K of the first 1M as exTENded memory? I have an AT&T 6386/SX WGS (16 MHz 80386SX box). It comes with 2 MBytes of RAM, which it calls: 640Kb basic memory 384Kb dedicated memory 1024Kb extended memory During its setup, you can enable/disable shadow RAM for both the BIOS and the EGA/VGA ROM. You can also specify that the remaining dedicated memory can be used as extended memory. I have done so, and during the bootstrap it claims that 256Kb have been moved from dedicated to extended memory. Tom Roberts AT&T Bell Laboratories att!ihlpl!tjrob
orand@kuhub.cc.ukans.edu (02/15/90)
In article <1990Feb11.191736.7917@agate.berkeley.edu>, ilan343@violet.berkeley.edu writes: > How many of the 386/AT motherboards out there are able to assign the > top 384K of the first 1M as exTENded memory? > > This question was discussed a while ago in this news group, but I don't > remember seeing a definite answer. > > I know the DTK/386 20Mhz motherboard (with a DTK BIOS) can do it. > However, I haven't seen any other motherboards used by low-end clone > makers that claim this capability. If you believe the sales people in > the stores I went, once you disable the ROM shadowing in their machines > those memory locations (the top 384K) are lost. > > Why is the DTK machine different? Motherboard, BIOS, memory > configuration? I have a nameless clone 286 motherboard that is able to assign the memory above the 640k as extended. The only problem is that when I put my 4Meg EMS board in, this memory is lost. Instead of reporting 5 Meg of memory, my system reports 4+640k (whatever that turns out to be.) Anyway, this was off the topic, but I wanted to let you know that other generic boards will use the 384 as extended. brady... =========================================================================== Brady Orand - University of Kansas Computer Center Lawrence, Ks. 66045 ORAND@kuhub.cc.ukans.edu Work: (913) 864-0490 Home: (913) 749-1341 ===========================================================================