Author: Robert Hyatt
Date: 10:29:55 07/06/03
Go up one level in this thread
On July 05, 2003 at 17:44:17, Tom Kerrigan wrote: >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? Can't read? 8080 -> 8085 -> 8086 -> 8088 and now they are almost "out" of new numbers, so 8086 -> 80186 -> etc. Same family from the start. > >>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. This is no "play land". Just research the _first_ "personal computer". Hint: MITS. Albuquerque, New Mexico. Tell me what processor "started it all". And while it may well be true that the 8080 and 8086 were not binary compatible, they were certainly _architecturally_ compatible. My electronic chess board source compiled and ran with nothing more than adjustments for the changed way the new processor did I/O as compared to the old S100 bus my 8080/z80 machines used. > >>>>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. > _clearly_ the 8088 was a kludge. If you look at the bus specifications, the nonsense about reading two bytes in two cycles was a kludge from the get-go. A necessary one if using old 8-bit memory was important, to be sure, but a kludge is a kludge. (Kludge == doing something in an ugly or inelegant way.) >>>>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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