Messages in this thread | | | From | Albert Cahalan <> | Subject | Re: older gcc and pentium | Date | Tue, 5 Mar 1996 15:46:55 -0500 (EST) |
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> On Mon, 4 Mar 1996, Mike Castle wrote: >> Amazingly enough Kai Schulte said: >> >>> Really 486? Don't the -m486 alignments bloat the code unnecessarily? >> >> Well, if using more memory results in faster memory accesses, is >> it unnecessary? The alignments result in faster code accesses. >> But if you have limited core, perhaps the compact code is more >> appropriate. > > It results in more speed for 486-specific accesses, but not for a 386, > and not necessarily for a 586, either. Can somebody with "real" hardware > knowledge help out on this? I really don't know enough about the > architectures, but i'll take a closer look at the new gcc as soon as I > have the time, promised ;)
Actual test results for non-kernel code indicate that 386 optimized code runs about 5% faster than 486 optimized code. This may vary depending on your cache performance.
Recent kernels can use 486+ opcodes, so there is a tradeoff here that has not been tested. For the very fastest code (assuming you do not upgrade your compiler) I'd guess that you should _compile_ for a 386 but set the #define for 486.
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