How CPU's work (was Re: Hi, I'm new...)
THX1138 at dakotacom.net
Sun Aug 6 14:52:00 CDT 2006
Chuck Guzis wrote:
> On 8/6/2006 at 10:39 AM Don wrote:
>> The "problem" with the MPU was putting it in a "computer".
> ...and that's really the nub of my argument. I have no quibble with the
> application of an MPU to play MP3s, run a scanner or traffic signal, but
> the huge mistake IMOHO, was trying to turn them into "Gemeral Purpose
Exactly. And the "PC" has now become little more than an
"Internet Workstation" for The Masses (I wonder to what extent
this is also true in Business?)
If the Google vision materializes, we'll be back to the
"mainframe with terminals" architecture -- though those
"terminals" will be considerably more graphical and
empowered AND the "mainframe" will undoubtedly be a cluster
of boxes instead of a single chassis.
> Computers". I'm not proposing that large-scale integration was wrong--it
> alone would reduce the size of your "washing machine" to a deskop box.
> Heck, my mouse has a PIC in it--but I'm not about to try to put a word
> processor or a DBMS on it. We're still living with the legacy of the 8080
> and CP/M in Windows.
Yes. Amusing that we don't have "USER0" and "USER7" areas on
C:, D:, .... :-(
> Not your post, but Dave's. While it's true that there were a significant
> number of major differences between the 8008 and the 8080, the architecture
> from a software point of view was set in the 8008. Accumulator, B,C,D,E
> registers; H,L handled as a pair to address memory; basic instruction
> layout, etc. The addion of SP and 16-bit addressing was a welcome
> addition, as were 16 bit adds and loads and 256 I/O ports, but to my eye,
> the 8080 looked like a tarted-up 8008. One valuable aspect of the 8008
> lost was the treatment of 00 and FF as HALT instructions.
Well, put a 0x76 at 0x0038 and 0xFF is effectively handled.
I particularly *like* the fact that 0x00 is NOP -- it lets
you scribble over portions of PROMs that you no longer want
without having to scrap the device entirely.
> Also, I'm not saying that the CP1600 was a speed demon--AFAIK, aside fromt
> he Activision games, it found no general application. Yet, from a
> programming standpoint, the closest thing to it prior to the 68000 was the
> LSI-11 (not a speed demon either).
> Sometimes, the actions of the people inside the micro business made me
> wonder. When I put my first hard disk (a 14-inch Shugart) on an 8085, I
> noticed that there was no one offering disk backup utilities for micros. I
> still have the rejection letter (along with the 8" floppy) from Lifeboat
> saying that they didn't think there was any market for a hard disk backup
> package. What I found incredible was the reinvention of mistakes. How
> long was it before the micro database people realized that atomic logging
> of database operations was worse than useless--that one had to log entire
> transactions? Mainframe people knew that before there were even micros.
This is largely a consequence of the fact that the MPU-based
world essentially "started over". E.g., why do we have limits
on the sizes of disk volumes (even in the *Sun* world?).
Why do we have Y2K problems? I mean, can't people *see*
that disks WILL get bigger, that the calendar *will*
continue beyond Dec 31, 1999, etc.?
Sure, some of it is resource-bound (e.g., who would need
anything bigger than FAT12 for a ~1MB floppy?). But, other
things are false economies brought about by lack of vision
and laziness on the part of implementers. (are Suns *that*
squeezed for resources that they have to save a few *bits*
to force the IPL to reside in the first 2GB of a drive??)
I don't think the problem is the MPU as much as it is the
fact that "competition" has disappeared from *that*
(desktop) marketplace. It's just one or two architectures
that are being rehashed over and over and over and...
Some of the earlier architectures were much more innovative
and expressive... but they just went away. As did many of
the OS's and applications. The same is true of even newer
"inventions". They get driven to "marketable" products
at the expense of good features, reliability, etc.
(e.g., Inferno is a neat idea that is quickly being
subverted by market pressures).
<shrug> Maybe we should al have become PLUMBERS! After
all, WC's haven't changed *that* much in the past 100 years... :>
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