strangest systems I've sent email from

Fred Cisin cisin at xenosoft.com
Tue May 24 16:10:53 CDT 2016


On 22 May 2016 at 04:52, Guy Sotomayor Jr <ggs at shiresoft.com> wrote:
> Because the 808x was a 16-bit processor with 1MB physical addressing.  I
> would argue that for the time 808x was brilliant in that most other 16-bit
> micros only allowed for 64KB physical.

Whether 8088 was an "8 bit" or "16 bit" processor depends heavily on how 
you define those.
Or, you could phrase it, that the 8 bit processors at the time handled 
64KiB of RAM.  The 808x still could see only 64KiB at a time, but let you 
place that 64kiB almost anywhere that you wanted in a total RAM space of 
1MiB, and let you set 4 "preset" locations (CS, DS, SS, ES).  There were 
some instructions, such as MOV, that could sometimes operate with 2 of 
those presets.
Thus, they expanded a 64KiB RAM processor to 1MiB, with minimal internal 
changes.


As opposed to starting over from scratch, ala Motorola.

Starting over from scratch made it possible to build an arguably better 
processor, whereas doing minimal changes reduced (and sometimes even 
eliminated) the need to rewrite existing code.
Which is more important - theoretically better processor, or availability 
of existing software?   Not everybody would choose the same.

It was claimed that in porting Wordstar to PC, Micropro took longer to 
change the manual than to get the software working.
Accordingly, software availability for the PC was more "immediate" than 
for the Mac.   Both had extensive software availability by the end of the 
1980s, but how about during the first 6 months after release of the 
machine?

Since "Nobody programs in assembly any more, nor ever will again" 
(-Clancy/Harvey), that isn't as big a deal as it once was.



(OB_Picky:  Due to the overlap of segment and offset, on machines that had 
21 address bits, real mode actually had a maximum of 1114096 (10FFF0h) 
bytes, instead of 1048576 (100000h).  That was accessed by HIMEM.SYS at a 
time when memory space was scarce enough that another 64K could make a 
big difference.)



More information about the cctalk mailing list