> And here it is - the first one with the current configuration of 12.5Mhz,
> and the second one forcing the PMAZ-A driver to configure as a 25Mhz clock.
> Note that it does indeed take twice as long to probe the devices.  The
> times also match what I would expect:  250ms * 2 probes * 7 devices =
> 3.5 seconds.

Things are getting clearer to me.  Does your NEWASC kernel have any
SCSI devices on PMAZ-A option card?  (People, we are discussing NEWASC
driver, not NetBSD/pmax old ASC driver)

> Data sent from the 53C94 would be sent at
> 1/2 the expected rate.  Most, if not all, targets devices shouldn't
> be bothered by that - it just means the data would be transferred
> half as fast.

I have two NEWASC kernels with differenct sc_freq values;

o With "12.5MHz" PMAZ-A;

asc1 at tc0 slot 0 offset 0x0: NCR53C94, 12MHz, SCSI ID 7
scsibus1 at asc1: 8 targets
probe(asc1:3:0): max sync rate 3.01Mb/s
sd2 at scsibus1 targ 3 lun 0: <QUANTUM, EMPIRE_1400S, 1022> SCSI2 0/direct fixed
sd2: 1335MB, 3053 cyl, 8 head, 111 sec, 512 bytes/sect x 2734996 sectors

IOZONE reports;
        1233618 bytes/second for writing the file
        1086044 bytes/second for reading the file

o And with "25MHz" PMAZ-A;

asc1 at tc0 slot 0 offset 0x0: NCR53C94, 25MHz, SCSI ID 7
scsibus1 at asc1: 8 targets
probe(asc1:3:0): max sync rate 6.25Mb/s
sd2 at scsibus1 targ 3 lun 0: <QUANTUM, EMPIRE_1400S, 1022> SCSI2 0/direct fixed
sd2: 1335MB, 3053 cyl, 8 head, 111 sec, 512 bytes/sect x 2734996 sectors

In this case IOZONE reports;
        1245339 bytes/second for writing the file
        1081006 bytes/second for reading the file

There is no large difference between kernels.  Difference would be
'longer timeout', exclusively?

Tohru Nishimura
Nara Institute of Science and Technology