$#%&%%$ 286 Dos Merge

[wtr at moss.ATT.COM]

In article <250 at obie.UUCP> wes at obie.UUCP (Barnacle Wes) writes:
>In article <1893 at qetzal.UUCP>, rcw at qetzal.UUCP (Robert C. White) writes:
>> The only thing I noticed that was wierd about this machine is that
>> I had to put exactly 640k of 120-ns ram chips on the motherboard.
>> There are 512k of 256k drams and 128k of 64k drams.  All chips are
>> rated at 120ns.  When I tried to put 1 megabyte on the motherboard,
>> all kinds of memory errors would result.
>
>You need 100ns RAM to run at 10 MHz.  The probable reason for the
>memory errors when you put one meg one the board are due to the way
>most AT boards map the memory. [...]  Your extended memory board
>was probably overlapping this address space and the two were
>conflicting.

Or it could be the way that your motherboard addresses it's chips.
Check if the board supports only 640K on the motherboard.  If it
does, then there's no way you can boost this to 1 Meg.  Your board
will refuse to map that extra 384K, or do nasty things like trying
to map it over the rom and the video buffers, which are located in
that upped 384K.  Other motherboards that have specific addressing
capabilities can handle that memory by either disabling the upper
384K (ala Sperry IT), map the entire upper 512K to the region of
1M-1.5M (also Sperry IT) or split it and map the upper 384K block to
the region above 1M (Sperry IT doesnt do.)

[ in case you havent guessed, i'm running V/AT on a Sperry IT :-) ]

If you try to use 256K's when the addressing scheme's only
expecting 64K's your going to have problems. 

Finally, i have seen 10 Mhz systems (my neighbors new toy ;-)
running 10Mhz 1 wait state with 120ns drams.

hope this has helped

=====================================================================
Bill Rankin
Bell Labs, Whippany NJ
(201) 386-4154 (cornet 232)

email address:		...![ ihnp4 ulysses cbosgd allegra ]!moss!wtr
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