Richard Fish wrote:
Colin wrote:
Maybe you can answer this question. I have an ATA/66 hard drive (66
MBps) on an ATA/133 bus. If the bus is limited to 133 MBps and the
drive cannot transfer data at more than 66 MBps, how come burst
transfers (as reported by hdparm -tT /dev/hdg) are at about 1.6 GBps?
Not that I'm complaining, of course, it just seems illogical :-)
Is it try-to-stump-Richard-day again already??? ;->
It is because of the way the -T test is implemented, which is to just
read the first block of data over and over again. Because hdparm
doesn't specify the O_DIRECT flag on open, the kernel will buffer the
data in system memory for the first read, and return the same for all
subsequent reads. So the number returned equals 1/2 of your system
memory bandwidth, since copying the buffer from one memory location to
another involves both reading and writing.
Oh OK. I thought the buffered result was kept in the drive's memory,
not the system's.
All right, since it's try-to-stump-Richard-day, let me throw out one
more question. This one should be easier. Pin 40 broke off this hard
drive's connector. The IDE specification says it's just a grounding
pin, one out of many on the connector, so it shouldn't hurt anything.
Right?
--
Colin
--
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