PA> The L1 cache is used for instructions. The more you have, the more
PA> instructions you can cache. The more instructions you can cache, the more
PA> you can do.
PA>
You are wrong (not you really but text above is wrong -- I am pretty sure that
you are undestood all this stuff right :-) L1 cache is used not only for
instructions cacheing but also for data cacheing (that's why there are 2x8K:
8K for instructions and 8K for data :-)... In this test case all instructions
and all data MUST be cached! If I am remeber right all modern processors are
4-way (at least) associative caches so even usage of library will not hurt
this...
PA> However, you run into the issue with cache block sizes. If you have 64K in
PA> 4 16K blocks, it will seem like you have 32K, because the latency will
PA> increase from having to address each cache block to get the instructions
PA> out of it. If you have a 64K cache in 32K blocks, you won't really notice
PA> any decrease. If you have 64K cache unified, it's a lot faster. Block
PA> sizes also count when you're doing LONG instructions. If you've got 8K
PA> blocks, and you've got a 24K instruction, it has to span three blocks,
PA> which gives you a MAJOR performance hit right there, because it has to
PA> waste cycles addressing and retrieving from each block, and then
PA> combining.
PA>
PA> So, in short; not only does cache size count, but cache addressing and
PA> block sizes.
PA>
PA> Oh, BTW, has anybody gotten their hands on the new Cyrix mII-300 yet? I
PA> don't want to order mine till I know how Linux likes 'em so far. I haven't
PA> had time to check the datasheets, much less print them, but as far as I
PA> can guess, with the kind of FPU performance I've been seeing from my
PA> 6x86MX's, they're using a dual-line FPU, which makes me wonder if that's
PA> going to raise any issues in the kernel. (No, mII-300 isn't Cayenne core
PA> yet. They're talking December or 1st Quarter 99 for the Cayennes, with the
PA> quad-line FPU. (Intel, eat your heart out.;))
PA>
PA> -Phil R. Jaenke (kernel@nls.net / prj@nls.net)
PA> TheGuyInCharge(tm), Ketyra Designs - We get paid to break stuff :)
PA> Linux pkrea.ketyra.INT 2.0.33 #15 Sat Apr 18 00:40:21 EDT 1998 i586
PA> Linux eiterra.nls.net 2.0.33 #15 Fri Apr 17 00:22:13 EDT 1998 i586
PA> - Linus says for 'brave people only.' I say 'keep a backup.' - :)
PA>
PA>
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