M. Warner Losh wrote: >Actually, ioport reads can be faster than the 1us that's widely >quoted. ioport reads can be as fast as ~125ns (2 cycles at 16MHz). >However, experience has shown that they are rarely this fast. I've >seen 8MB/s pio over the pci bus on some custom hardware we have, which >2Mreads/sec which is about 500ns per read. I think that the pci >hardware that I was reading had a few extra wait states... > >The 1us/read is for devices on the ISA bus or for hardware that >emulates this timing. > >Warner > > > > The ioport speed is also unstable, on my IBM T43 thinkpad notebook, if I load wireless driver, the gettimeofday syscall will be 4 times slower than no wireless driver loaded, though I am not using the wireless network. David XuReceived on Sun Oct 30 2005 - 23:37:06 UTC
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