I'm kind of surprised that this hasn't come up yet.
The original BIOS and the 2nd revision BIOS (Oct 1981) both had a cute
little bug in them where they would only count up to 544K of installed
memory. You might have 640K and have all of the switches set correctly,
but the BIOS bug caused the count to stop at 544KB.
What is the casue of this bug?
-tony