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2022-11-15, 07:37 PM (ISO 8601)Ogre in the Playground
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- Jul 2010
Did any "classic" 8-bit CPUs have an integer multiply instruction?
Did any of the "classic" 8-bit processors have an instruction to do 8-bit integer multiplication?
Originally Posted by Harnel
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2022-11-15, 09:34 PM (ISO 8601)Bugbear in the Playground
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- Feb 2015
Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
I don't see it in the instruction sets for the 8080, the Z80, or the 6502. The manual for at least one of those describes how to do integer multiplication using bit tests, shifts, and adds.
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2022-11-15, 10:53 PM (ISO 8601)Ogre in the Playground
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- Jul 2010
Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
So far, the earliest "popular" CPUs used in consumer products to have an unsigned integer multiplication instruction I've found are the 16-bit 8086 and the 16/32-bit 68000. I've just been blindly looking at individual processor specs, though. I don't have any particular expertise to help me find a good answer quickly.
Last edited by gomipile; 2022-11-15 at 10:57 PM.
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2022-11-16, 03:24 AM (ISO 8601)Ettin in the Playground
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- May 2009
Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
An 8-bit instruction set is inherently very limited, and so is the hardware it runs on. I think there's a good chance that what you're looking for doesn't exist.
(I learned machine code programming on a Z80. It's been a while since I've given the subject much thought, but I can still say with confidence that if you wanted to multiply something on that platform, you had to go a long way around.)"None of us likes to be hated, none of us likes to be shunned. A natural result of these conditions is, that we consciously or unconsciously pay more attention to tuning our opinions to our neighbor’s pitch and preserving his approval than we do to examining the opinions searchingly and seeing to it that they are right and sound." - Mark Twain
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2022-11-16, 11:58 AM (ISO 8601)Troll in the Playground
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- Nov 2006
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- England. Ish.
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Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
Unless, of course, you wanted to multiply by two, in which case you had lots of instructions to do it... Originally Posted by veti
(The shift instructions do just that - otherwise there's two pages of routines in the Z80 handbook I just checked, and I can't get to the other Z80 handbook as its on a lower shelf behind the TV and assorted junk from my in-law's place)Warning: This posting may contain wit, wisdom, pathos, irony, satire, sarcasm and puns. And traces of nut.
"The main skill of a good ruler seems to be not preventing the conflagrations but rather keeping them contained enough they rate more as campfires." Rogar Demonblud
"Hold on just a d*** second. UK has spam callers that try to get you to buy conservatories?!? Even y'alls spammers are higher class than ours!" Peelee
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2022-11-16, 03:01 PM (ISO 8601)Ettin in the Playground
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- Jun 2013
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- Bristol, UK
Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
I asked here:
http://www.yakyak.org/viewtopic.php?f=20&t=89152
The answer seems to be a pretty near definitive "No".
The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.
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2022-11-29, 02:00 PM (ISO 8601)Ettin in the Playground
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- Jun 2013
- Location
- Bristol, UK
Re: Did any "classic" 8-bit CPUs have an integer multiply instruction?
Later in the same thread, we got:
Originally Posted by gravy
Which is a Yes. So that's a 180 degree turn.Last edited by halfeye; 2022-11-29 at 02:01 PM.
The end of what Son? The story? There is no end. There's just the point where the storytellers stop talking.
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