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On Monday 02 June 2008, Mikkel L. Ellertson wrote:
>Cameron Simpson wrote:
>> On 02Jun2008 02:09, Gene Heskett <[email protected]> wrote:
>> | Jump tables scattered around in your code, taking up valuable space cuz
>> | the darned thing doesn't have a conditional long branch ability, just
>> | for starters.
>>
>> Hmm. I don't seem to recall needing jump tables, but perhaps my code
>> was smaller than yours. In fact, I've got some z80 code right here [...]
>> The long jump JP command allows conditionals. The 8080 might not have;
>> I never used that, either.  I did have a Z80 macro for measuring the
>> length of the jump and using a JR instead of a JP where possible, but
>> JPs definitely allowed conditions.
>
>The 8080/8085 had jump to an absolute address, with or with out
>conditions, but did not have the jump relative that the Z80 did. So
>even for a jump of 126 bytes away, you had to use the 3 byte jump
>instructions.
>
>Mikkel

I'll have to plead that it was 27 years ago that I fought with it cuz the 
conditionals I wanted to use were all limited to signed 8 bit offsets, so to 
reach the nether regions of a lowly 2732, I had to have space for a long jump 
handily near the conditional.  I have a copy of Zack's book on the top shelf 
but that's is only 9" short of the ceiling in here, out of reach without 
something to climb on that is steadier than this office chair.  I was running 
two Z80's against each other with 17 miles of dry wire between them (FM 
transmitter ATS) & one kept crashing, turned out the $EB command (swap register 
sets) was being ignored about 5% of the time.  Loverly, and zilog told me to go 
pi** off when I asked for a good chip, and I haven't pointed a 10 foot pole at 
one of them since.  I wonder how much repeat business they ran off with that 
attitude, they sure ran me off.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Parallel lines never meet, unless you bend one or both of them.

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