IBM 5150 maximum memory?

Jim Leonard trixter at
Fri Apr 25 22:29:40 CDT 2008

Fred Cisin wrote:
> On Fri, 25 Apr 2008, Michael B. Brutman wrote:
>> I'm kind of surprised that this hasn't come up yet.
> It's been referenced over and over without the details.
>> 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
> THAT'S the "about but not exactly 512K" number that we've been looking
> for.
> Once you finally found out about it, it wasn't too hard to patch.

Where?  DOS?  Somewhere in the BIOS data area?

I ask because I just received an Oct 1981 BIOS 5150 and would like to 
use all of the memory :-)
Jim Leonard (trixter at  
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