IBM 5150 maximum memory?

Guy Sotomayor ggs at
Sat Apr 26 16:02:22 CDT 2008

Y'all need to re-read my post a couple of days ago.  BIOS was there  
mainly for ROM/Cassette BASIC (the *only* PC to do that).  The  
original choice for OS was CPM, but that story has been well told.

Although I wonder how many people realize the inside joke of one of  
the BASIC demo programs?  And who says IBM doesn't have a sense of  

On Apr 26, 2008, at 12:55 PM, Tony Duell wrote:

>> That's not the first time you've mentioned that, so now I have to ask
>> you:  What's the #1 most glaring misdesign you can remember about the
>> 5150 or 5160?
> Oh, that's easy. The edge-triggered active high interrupts.
> And on the software side, the fact that the BIOS serial port routines
> don't use interrupts, making it necessary ot hit the hardware  
> directly if
> you wanted any decent data rate without dropping characters. You  
> know, I
> was under the impression that the whole point of device driver  
> routines
> was so you could make different physical hardware look the same to the
> applicaiton programs.
> -tony

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