IBM 5150 maximum memory?
eric at brouhaha.com
Sat Apr 26 13:01:59 CDT 2008
> I realize that IBM didn't expect the PC to have
> the life it did,
> Moore's law was at the time a well known trend, and it wouldn't take a
> genius to calculate that the 16-fold increase in memory would be outrun
> in just a few years.
Reed your first statement I quoted above again.
Anyhow, even if they had put the video at 0xE0000, Moore's law *still*
would have resulted in the machine running out of address space, and
that wouldn't have been delayed by even a year, so whether they ignored
Moore's law in picking the address of the video card is completely
And although it wasn't obvious from the original tech ref and BIOS
listing, they probably expected there to be other memory-mapped
devices above 0xA0000, and firmware extensions.
Even though we (the users and programmers) didn't like the video
being at 0xA0000 by the mid-1980s, I don't think it can really be
considered a huge mistake. They left room for more than half a
megabyte of RAM. I'm not aware of any other mainstream microcomputer
introduced in or before 1981 that could support contiguous, directly
adressable RAM configurations from 16KB to over 512KB.
[Geez, I can't believe I'm defending the engineers that developed
the PC. Now I feel like I need to take a shower.]
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