Intel 80386, a Revolutionary CPU
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Intel 80386, a Revolutionary CPU
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Re: Intel 80386, a Revolutionary CPU
#2How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
Re: Intel 80386, a Revolutionary CPU
#3How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
In specialised applications, you'd definitely miss AVX and SSE. Beyond that, I'm not sure.
Re: Intel 80386, a Revolutionary CPU
#4They were in big trouble then. The entire company was riding on it being great.
It could have easily gone awry as it did for Data General, Honeywell, CDC, AST, Tandy, Olivetti, Xerox, DEC Rainbow, AT&T Hobbit, Wang 2200 and Unisys. Strong survivorship bias on this one. Most of the once Titans are in or near the dustbin now, such as SDS, SDC and Fairchild.
Intel's history was primarily as a memory manufacturer. They're arguably near a similar fucked position now - effectively 0% of the mobile and home appliance market and getting slaughtered in their only remaining stronghold by NVIDIA, AMD and ARM pillaging their castle. Hopefully they'll squeeze out of this one.
Re: Intel 80386, a Revolutionary CPU
#5How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
Vector instructions are the obvious thing and being massive gains to media, cryptography, math, AI, graphics, and signal processing.
Beyond that there have been a few additions like CMOV (conditional move) that would be missed, though instruction fusion in pipelines can sometimes achieve the same speed up.
Lastly you would have to add some atomic instructions to support SMP.
Re: Intel 80386, a Revolutionary CPU
#6How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
I think the early Pentiums are pretty close to the instruction set of the 80386. However there were many iterations to the Pentium that added new instruction like the MMX.
Re: Intel 80386, a Revolutionary CPU
#7How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
80486 and Pentium added relatively few instructions to the core instruction set, but there are a couple of pretty important tools which got added. The ones you'd miss the most would probably be:
* CMPXCHG (486). Central to multiprocessor synchronization and locking.
* CPUID (P6). Admittedly, if the instruction set were frozen you wouldn't need this... but if not, it's how you detect what CPU you're running on and what it supports.
* RDMSR/WRMSR (P6, kernel only). A general-purpose mechanism for adding extra special-purpose registers to the CPU without having to allocate an instruction to each one.
* INVD/WBINVD/INVLPG (486, kernel only). This was the first Intel CPU to support cache; these instructions were used to manage it.
Re: Intel 80386, a Revolutionary CPU
#8They were in big trouble then. The entire company was riding on it being great. It could have easily gone awry as it did for Data General, Honeywell, CDC, AST, Tandy, Olivetti, Xerox, DEC Rainbow, AT&T Hobbit, Wang 2200 and Unisys. Strong survivorship bias on this one. Most of the once Titans are in or near the dustbin now, such as SDS, SDC and Fairchild. Intel's history was primarily as a memory manufacturer. They'r…
What’s their hope right now? Some sort of Quark-derived desktop CPU à la Dothan?
Re: Intel 80386, a Revolutionary CPU
#9How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
The 486 added XADD, BSWAP, CMPXCHG, INVD, WBINVD, INVLPG to the instruction set.
The original Pentiums added CPUID, CMPXCHG8B, RDTSC, RDMSR, WRMSR, RSM to the instruction set.
Later Pentiums added the MMX instruction set.
Re: Intel 80386, a Revolutionary CPU
#10How different are the instruction sets of the 80486 and Pentium from the 386? Put another way, had the instruction set been frozen as of the 386 (barring any required changes for 64-bit), would we notice any difference in performance today?
80486 and Pentium added relatively few instructions to the core instruction set, but there are a couple of pretty important tools which got added. The ones you'd miss the most would probably be: * CMPXCHG (486). Central to multiprocessor synchronization and locking. * CPUID (P6). Admittedly, if the instruction set were frozen you wouldn't need this... but if not, it's how you detect what CPU you're running on and wha…
CPUID was available on late-model 486s too.