ccenol@rivm.UUCP (Arnold Reinders) (09/13/88)
I would like to thank everyone for their answer upon my AT-memory split
problem. Below follows a summary of most remarks. The summary of that is
that there is no solution of the problem because it's a bug on the
motherboard. One workaround is to fill two banks with 64K bit chips and to
add memory boards. Another solution is to have just 512K byte on the
motherboard, add a Zucker extended memory board which backfills to 640 Kb.
Thanks everybody and I hope that this summary will help others with the
same problem.
Arnold
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I had the exact same problem. There is no solution except...... Go out and
buy a Dr. Dr. Zucker Extended memory board. This will let you backfill up
to 640k and use the rest of your memory as extended mem. I am doing this
right now and it works without any problem. Please note that the chips must
be rated at 120ns or better to work with the expansion board. The cost:
~$80.00.
Jonathan Joshua jjoshua@topaz.rutgers.eduThis is a common problem, and
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it is likely that there is no workaround. The reason that it is common is
because to do it "correctly" (640+320), would mean that two parts of a
single RAM chip must be addressed in two different places. (Remember that
1Meg is only 2 banks of 256K rams). It isn't IMPOSSIBLE to do this, but it
is common botched in the cheap clones. Some machines allow you to fill the
second "bank" of memory with 64K rams instead of 256K's, avoiding any
wasted RAM (but still leaving you without any extended memory on the
motherboard).
john nelson {decvax,mit-eddie}!genrad!teddy!jpn
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That is the way it is on many older design AT clones. My Unisys IT came
with 512kb main memory. To go to 640K I had to buy a full 512k and waste
384k. Such is life. On newer design boards, you only have to get the 128k
extra. There is no way to go above 1meg easily on the mother board.
Richard Marks rmarks@KSP.unisys.COM
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This seems to be a common problem. Maybe it gives a simpler design of the
mainboard. I have a Bondwell AT computer, and it behaves exactly the same
way.
Per Andersson perand@tds.kth.se
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Your dealer is probably right, in this case. If you are using 256K chips,
a complete bank is 512K (since the AT uses a 16 bit address bus). Most
manufacturers (including those who make expanision boards) do not add the
circuitry to split a single bank into separate address areas i.e. all the
chips in the bank must be set to the same memory block, either the 512K
starting address or the 1 Meg starting address.
Bradley Dyck Kliewer bkliewer@iuvax.cs.indiana.edu
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Bad news, I have such a machine too. (maybe even the same) [I've got a
Genisys Challenger, Arnold]. I've also tried various tricks, but couldn't
use the remaining 384K with 640K main memory active. I think it is more a
design descision of the manufacturer in stead of a bug.
Richard Ronteltap richard@neabbs.UUCP
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You are probably SOL. If your motherboard uses CHIPS devices which are not
of the NEAT flavor, you are definitely SOL. Look for the 82C202 chip. I
don't know about Zymos or whoever. What I do is put 64K chips in the
motherboard's second bank, as they are real cheap. Then if I had the extra
256K chips, I'd buy a expanded memory board and use it as RAM cache. Why do
Big-Endians number their bytes backwards from their bits? I speak for
myself, not the company.
Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or phil@amd.com
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The problem of 512 kb + 512 kb ext or 640 kb with 0 kb ext is a fault in
the main board. It's not a bios problem but a hardware problem. I've the
same problem and it can't be solved by my dealer. The only solution is to
put 512 kb + 128 kb on the main board and the other 512 kb on a extended
memory board +/- F 200,- with 0 kb. I have done that.
Hans Varkevisser hans@let.vu.nl or let.vu.nl!hans
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There is no way to konfigure an AT Clone with 640 k RAM and 384 K extended
! On most AT clones ther is no Hardware to support this konfiguration
(because it's too expensive). We had the same problems and didn't solve
them 'til now ! So, there is no reason to insert 1 MB RAM into such an AT
Board. Solution: Use extended memory card ....
Dirk Bolte <mcvax!exunido.irb.informatik.uni-dortmund.de!bolte>