I apologize to Michael that I made light of your first
information "option DEBUG."

>   I can think of a couple of things contributing to this.  The first one is
> that the NetBSD driver currently allocates a "DMA buffer" for the IOASIC
> SCSI.  All data transfers have to be copied to/from this buffer.  The IOASIC
> SCSI is capable of doing DMA directly to memory, but the NetBSD driver does
> not currently utilize this capability.  The second reason is related to
> copying data to/from the DMA buffer memory:  the DMA buffer memory is in
> uncached memory space.  Utilizing cached memory for the DMA buffer seems
> to help the iozone reading rate a bit, presumably because the data copies
> are a little quicker.  I've been running my kernels with cached memory
> with no apparent ill effects for a while now.  [I had done this while getting
> the R4000 mods working].  If anyone wants to test this, just make the
> following change in sys/dev/tc/asc_ioasic.c:

According to your information, I changed asc_ioasic.c and
machdep.c. The new kernel gives following wonderful result.

        1327791 bytes/second for writing the file
        1784159 bytes/second for reading the file

The changes in machdep.c are only the mystery...

Thanks,

Takuya.
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