Anonymous Coward wrote on 2020-08-17, 07:52:
The 80286 isn’t *that* advanced. It’s main claim to fame is that it has a seldom used protected mode. Most of the extra speed comes from the 16-bit memory. An 8086 should be 80% as fast as a 286 at the same clock speed.
"The 80286's performance was more than twice that of its predecessors (the Intel 8086 and Intel 8088) per clock cycle. In fact, the performance increase per clock cycle of the 80286 over its immediate predecessor may be the largest among the generations of x86 processors. Calculation of the more complex addressing modes (such as base+index) had less clock penalty because it was performed by a special circuit in the 286; the 8086, its predecessor, had to perform effective address calculation in the general ALU, taking many cycles. Also, complex mathematical operations (such as MUL/DIV) took fewer clock cycles compared to the 8086."
Source : http://www.computinghistory.org.uk/det/6187/I … 00-transistors/
Edit: Comparing is difficult here. It's like comparing a 6502 and an 68010.? 😁
The 80186 and V30 are closer to the 286, I believe. The V20/30 is a real CPU, also.
It reminds me a lot of the Z80, which used hard-wired instructions instead of microcode,
and was more advanced than the 808x, also, despite being from a previous generation.
Ironically, the Z80 could work with 16-Bit values, despite having an 8-Bit adress-space (64KB) only.
In some way or another, this is like the old i8080 vs Z80 rivalry.
Anyway, I try my best to be open-minded in this case.
Would be interesting to find out the"truth".
Maybe that's a case for the Mythbusters? 😉
Edit: There's something else that comes to mind: BIOS performance.
The original IBM AT had a very limited BIOS, which wasn't optimized really and lacked a ROM Setup.
Back in the 80s it was not uncommon to use an alternate BIOS, like the one from Quadtel.
This makes me wonder how much performance was bottlenecked because of the BIOS in general. We're the ROM chips interleaved? Was access time 70ns or 250ns?
Did the Turbo XTs use Shadow Memory (BIOS copied to RAM)? Did Turbo XTs use waistates?
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
//My video channel//