On Fri, 9 Feb 2001, Jun Sun wrote: > Do you like run-time detection better because it allows a kernel to run on > CPUs both with a FPU and without a FPU? Or there is something else to it? Nope. There are certain explicit actions that are to be performed by the kernel if a real FPU is present, such as saving and restoring its registers or setting the control register. Therefore the kernel has to know if a real part is present and act accordingly. Maintaining a table of all CPU ids ever manufactured and manually setting the FPU presence bit is unreliable, especially as there are chips which cannot be classified this way, e.g. knowing your CPU is an R3000A you don't know if an R3010A FPU is soldered as well or not. > Another question. I know with mips32 and mips64 we can do run-time detection > reliably. What about other existing processors? I've sent a quote from an IDT manual recently. It recommended to use the FPU implementation ID to check if an FP hw is present. I believe it should work for any sane implementation of a MIPS CPU. See the mail for details. Maciej -- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
