RE: 768k XT?

["Riley Williams" <Riley@Williams.Name>]

Hi Dan.

 > Hopefully someone knows, I have a Samsung XT clone that has
 > 3 banks of 256k chips, so that would mean a total of 768k or
 > memory. The BIOS memory check reports 640k, so I'm wondering
 > if there really is 768k available somehow, or if it was just
 > cheaper to use 256k chips and leave a few k unused.

I don't know that particular box, so can't comment there, but...

 > Has anyone ever run into this before?

I've run into similar - in my case, a Kyoshui XT with 4x256k
mapped as 640k of normal RAM and 384k of EMS RAM (permanently
in the D0000-DFFFF address range.

Technically, it's possible that one of the 256k banks has one of
the address pins permanently tied either high or low, and thus
that the extra 128k isn't mapped anywhere as a result.

 > Is anyone familiar with any other boards that allowed the use
 > of 256k parts in place of the 64k chips in order to add some
 > upper memory?

Other than the above, no.

 > Does anyone have any DOS utilities or ELKS utilities that
 > would test for upper RAM even though the BIOS says it's
 > not there?

As far as RAM above 1M is concerned, the XT processors don't
support it.

Best wishes from Riley.
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