Author: Tom Kerrigan
Date: 14:44:17 07/05/03
Go up one level in this thread
On July 04, 2003 at 23:49:25, Robert Hyatt wrote: >>>The _first_ was the 8080 and it was _not_ a 16 bit cpu. The 8086 was the >>Uhhhhhhhhhhh, Bob? Does it make a lot of sense to call the 8080 an "x86"? Hint: >>there's a reason why the 8086, 80186, 80286, 80386, and 80486 are called "x86"s. >>Can you think of what that reason is? >Yes. Do you know why the 8086 was called the 8086? Because it was a >"new and improved" 8080. Notice the number simularity? However, they >"ran out of numbers" and inserted a digit in the middle. But the 8080 Uhh, which number do you insert in the middle of 8080 to get 8086? >was the beginning of the product line. I have one sitting in my office >that still runs. Alongsize a Zilog z80 that was its direct competitor >and which drove Intel to develop the 8086. Sure, the 8086 is an improved version of the 8080, but that doesn't make the 8080 an "x86." Besides the obvious argument that "8080" doesn't end in "86," notice that all x86s are binary compatible with each other (backwards compatible, anyway) and the 8086 is NOT binary compatible with the 8080. >>>second processor and it was compatible with the 8080. Each 80X86 processor >>No, the 8086 ISA is similar to but not compatible with the 8080 ISA. And the >>8086 was not "the second processor." It was Intel's 5th processor. 4004, 8008, >>8080, 8085, 8086. >It was the _second_ processor in "the line." I had an 8008 for example, >and it was "bare bones". The 8080 was the first usable uprocessor. Otherwise >you could go back farther than the 4004. IE they had a 1, 2 and 4 bit ALU >in the 7400 series. No, you can't, because an ALU isn't a microprocessor. Intel is credited by everybody with inventing the first microprocessor with the 4004. >>>ever since has maintained that compatibility. But it _started_ at 8 bits. >>Well, if you mean Intel started at 8 bits, no. The 4004 was a 4 bit processor. >Again, the first _real_ machines were 8 bit. the personal computer took off >when the 8080 and then the z80 came along. the 8085 and 8086 followed right >behind and with the 8086/8088 IBM's "PeeCee" was born. I'm not particularly >interested in things prior to the 8080 because they were _way_ different >internally. But the 8080 stuff started a trend of "upward compatibility" Well, nobody asked what you're interested in or what you think the first "real" machines were. When talking with other people, you have to step out of your imaginary play land. >>>The 8088 was a kludge, but it wasn't where I was talking about either. I was >>Depends on what you mean by a kludge. If you think the 8086 is a kludge, then >>yes, the 8088 is also a kludge, because they're the same except for the external >>bus width. But realize that having an 8 bit bus instead of a 16 bit bus resulted >>in SIGNIFICANT motherboard cost savings at the time. Saving a lot of money by >>sacrificing some performance is not a kludge, it's a trade-off. >The main savings was not on the motherboard. It allowed 8 bit memory boards, >as used by all the 8080/z80 processors, to be used "as-is". The S-100 bus >was the standard back then, of course. And the 8088 tried to leverage >existing memory technology to control price. Fortunately that nonsense didn't >last long. Fine, I won't argue with you because I haven't looked at the PC motherboard for years, but you're still supporting my point that the 8088's 8 bit bus was NOT a kludge but a cost saving decision. I mean, saying it's a kludge is like saying the Celeron is a kludge because it has half the cache of a P3/P4. >>>talking about the _beginning_ of the product line which went back to the >>>original 8080 which the current processors will still execute assembly code >>>from. >>Right, the assembly is the same but the chips are not binary compatible. When >>people say backward compatible they usually mean binary compatibility. >OK. You may be correct there. It's too far back to remember exactly, in my Thank god for the Internet then. >>No, the 8080 was an 8 bit processor with instructions that were 8 to 32 bits. It >>had 8 bit general purpose registers. >You mean (apparently) 8 to 32 bits long? As opposed to operand size? That >is not unlike the current instructions although they can be longer still. Right. -Tom
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