On Tue, 13 Jan 2004, Ralf Baechle wrote: > > You cannot modify the size of the primary caches -- the values are > > hardwired to the amount of cache available in the processor (8kB+8kB for > > the original R4000). However, if you take appropriate precautions, you > > can alter the line sizes of the caches by modifying appropriate bits of > > cp0.config. > > On some systems that's a dangerous and won't work due to some issue with > the memory controller. That's why Linux supports all possible combinations > instead of reconfiguring caches. Of course there's also the hope that > developers of a system did configure the cache for the optimal performance. Plus there are processor errata related to certain values of line sizes. > If reconfiguring is possible 32-byte D-cache and I-Cache lines are probably > the optimum for non-tiny systems. For the L2 cache I'd guess 64 or 128 > byte lines. Well, reconfiguring the line size of the L2 cache is system-specific and the size is most likely hardwired. BTW, the DECstation uses 16-byte lines for the D-cache and the I-Cache and 32-byte lines for the S-cache. With the S-cache size at 1MB and up to 480MB of RAM does it qualify as a tiny system? ;-) Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
