Old farts and new Linux

[Gene Heskett]

On Wednesday 05 May 2004 21:54, Jeff Ratliff wrote:
>On Wed, May 05, 2004 at 11:11:05AM -0400, Gene Heskett wrote:
>> Unforch Rodney Zacks left a couple of errors in that tome that
>> you'll probably discover when you do your first or second assembly
>> or machine code routine based on looking up the hex values in that
>> book and entering them with the monitor.  Been there, done that.
>>
>> Rodney's stuff for other platforms was more accurate.
>
>I seem to remember there where some important things in there that
>didn't quite match up. Mine was actually misprinted and had one of
> the later chapters printed twice. Whatever was in the missing
> chapter must not have been that important.
>
>It taught me binary and hex and basics of CPU architecture, though.
>That Z-80 was a hot little chip. Too bad IBM went with Intel
> instead. Imagine a Zylog based IBM PC running CPM-86 in 1981!
>
>OK, I better shut up now.

It wasn't that bad if you had a good one, I fought with one for weeks 
that would only execute the $eb command on alternate thursdays when 
it was raining.  $eb is the swap register sets command.  My biggest 
disappointment in that chip was the lack of conditional long jumps, 
you had to jump +126-128 for an address range, so you always wound up 
with a long jump table someplace in a page of code that had to be 
short jumped over by the code that was actually running.  Made your 
code look like it was laid out by a drunken rattlesnake od'd on 
uppers.  Moto's 6809 was a much smarter chip, and the hitachi 
replacement 63C09 they can't talk about in fact has the microcode map 
filled up completely.  How about 16x16 bit multiplies with a 32 bit 
result in 25 clocks, or a 32/16 divide with 16 bit remainder and 
dividend in 39 clocks worst case.  Also 32 bit loads and stores.  
Bear in mind its an 8 bit data buss chip we're talking about here.  
Oh, almost forgot, it also does PIC, something that was a totally 
foreign concept over at zilog.

Really, no valid comparison can be made between the two chips that 
will make the look Z-80 superior.

-- 
Cheers, Gene
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Copyright 2004 by Maurice Eugene Heskett, all rights reserved.