27 Jun
1998
27 Jun
'98
5:32 a.m.
'The DMA address extension register is a 4*4
register file
chip (74LS670) at location <U whatever>. It supplies the top 4 bits
of the system 20 bit address during DMA cycles. Unlike the
segmentation scheme used by the CPU, the extensions address is not a
16 bit segment address which is added to the address from the DMA
controller. Therefore, DMA operations cannot cross 64K boundaries',
I can half-understand that, but if you read those urban legends about a
guy calling tech support because the power went out in his block (I've
had personal experience - my mom thinks there is a significant
difference between a TV and monitor as far as cleaning solution is
concerned), I sometimes wonder how these people learn to walk :)
Now remember the PERQ again, and think back to the start of this (long)
thread. The PERQ happens to be the first commercial machine that would
now be classed as a workstation. For that reason alone it should not be
forgotten. But few people have ever heard of it (OK, not on this list
since I do go on about it :-)), or seen one. Which comes back to the
original point. Where should the average man in the street go to see
the
machines that led up to the PC he's now using
(I'll assume Windows, if
only because it's the most common OS).
The average man in England might get your book, the average man in the
US doesn't have time. Most people just _don't have time_ to learn about
curiosities, especially when such complex, multidimensional concepts are
involved. And so many people already have learned to use their computers
mechanically (I just turned it on and it always loaded WordPerfect...)
that such knowledge would have nowhere to go. I've seen some of my
classmate have trouble understanding how muscles work, because they
_just do_. Also, the economic forces that partly drove this stuff could
never be understood by the naive American. To bring this long rambling
to a close, I don't think many people would understand such a history,
though that does not mean that we shouldn't try to make them ;)
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