Re: 7200 RPM udma33 same speed as 5400 PIO mode 4
On Fri, Feb 11, 2000 at 01:53:43PM -0700, Rick Macdonald generated a stream of 1s and 0s:
> On Thu, 10 Feb 2000, Dan Melomedman wrote:
>
> >
> > Check out my interesting timings:
> > using_dma = 0 (off)
>
> If I turn off "using_dma", my 9.4 drops down to 5.2. None of the other
> switches make much difference except this one.
>
> ...RickM...
>
Even if your drive can do UDMA33, it is only useful for transfers from the drive's cache, since only they can reach that high transfer speed, so that's where speed-ups come from, also this puts less strain on your CPU. And remember IDE is 16 bit, really archaic. I bet if your machine was a bit faster, say 400 MHz with 100 MHz bus, you could reach ~12 MB/s with those drives. If you want my opinion, IDE SUCKS, but hey it's cheap! In my opinion IDE is only ok for a low-end workstation, if it's a busy server don't even bother with IDE. Also note that different IDE chipsets have different performance, but they all use up to 10% (or more on slow machines) of your precious CPU time. It's a pity that Ali Alladin 5 chipset is quite good, but support is not included in 2.2.x kernels :(. SCSI does it's own processing, and can do things in parallel, much better. Also most users don't tweak their set-up with hdparm and suffer unnecessary performance losses.
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