Author: Bo Persson
Date: 15:41:42 07/06/03
Go up one level in this thread
On July 06, 2003 at 17:41:19, Tom Kerrigan wrote:
>On July 06, 2003 at 13:29:55, Robert Hyatt wrote:
>
>>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.
>
>Read my other post to this thread, about the BMW 3-series.
>
>>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.
>
>Well, shit, my chess program compiles and runs on an Alpha with no adjustments
>at all. That must mean the Alpha is an x86 and it's architecturally compatible
>with the Pentium. ("Architecturally compatible"?? What kind of nonsense is that?
>Did you mean pin compatible?)
>
>>_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.)
>
>Reading two bytes over a one byte bus?
Except that it was actually a wider bus, but the full width wasn't used for
data, just for addresses.
The 20 bit address bus was multiplexed with an 8 bit data bus on the same pins.
Elegant - no. Super kludge - yes!
I still remember my amazement when I once realized that a slow multiply
instruction was faster than shift and add, because a MUL took long enough that
the poor 8088 had time to fill its 4(!) byte instruction queue with the next
sequence. My "optimized" shift and add sequence used instructions that executed
faster than they could be fetched, and left the processor starved. A definite
Super kludge.
Bo Persson
bop2@telia.com
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