Hello
Original question was whether Tru64 4.0F enables DMA mode
for IDE disks and if not can it be turned on.
I received two answers, thanks to both.
Only two so I include them here
Dr. T.Blinn says
>Use of IDE DMA is NOT a tunable option. I honestly don't recall if
>the person responsible for the IDE interface support in V4.0F ever
>got it working reliably; I suspect the answer is "no". Whether it
>works depends in part on which IDE chip is on the motherboard. The
>chances of it working in DMA mode increase with newer releases; I
>would be genuinely surprised if it's running in DMA mode in V4.0F
>on the DS10. I know who I would go ask, but I'm pretty sure that
>it doesn't do DMA.
Dirk Hufnagel suggested writing heavyly to disk and observing
cpu usage via top.
>As far as I know, the DS10 uses some Ali chip with integrated
>IDE incl. UDMA support. Since IDE disks are an official option,
>DMA should be on by default. That was different for the PWS
>(433au,500au,600au) where IDE officially was supported for the
>cdrom. Disks worked there too but it was horribly slow, eg.
>PIO mode with 100% CPU load as soon as you did anything
>with the disk.
>The difference between PIO mode and DMA mode are like night
>and day. Just run a tar job (w/o compression) or something
>similar on the IDE disk and look at the top output. It will
>be obvious if DMA is enabled.
I did write tests and cpu usage never went higher
than 14%. This suggest that at least PIO is not used, but
question still remains whether IO is interrupt driven or DMA based.
I don't know whether issue can be settled observing cpu usage.
Tapani
Received on Wed Feb 27 2002 - 09:09:28 NZDT