[ltp] T21, what ide speed?

Tom Allison linux-thinkpad@www.bm-soft.com
Wed, 17 Oct 2001 22:56:03 -0400

Dr. Edmund Weitz wrote:

> Sorry, I know this comes a bit late but I stored this message for
> future reference and was on vacation in the meantime.
>>From the kernel boot messages I guess that the idebus=xx parameter
> does only affect the hard disk if it is in PIO mode. (Is that true?)
> On my (SuSE 7.3) installation, the hard disk (IBM-DJSA-232, also on a
> T21) is automatically switched to DMA mode.
> I played around with different settings and found out that PIO with
> idebus=66 seems to be slower than DMA on my machine. But I also found
> out - to my astonishment - that the output of hdaparm -tT doesn't seem
> to be a reliable means to tune your hard disk. With the _same_
> settings (DMA) I got results that varied from
>   Timing buffer-cache reads:   128 MB in  0.80 seconds =160.00 MB/sec
>   Timing buffered disk reads:  64 MB in  3.55 seconds = 18.03 MB/sec
> to
>   Timing buffer-cache reads:   128 MB in  1.25 seconds =102.40 MB/sec
>   Timing buffered disk reads:  64 MB in  7.82 seconds =  8.18 MB/sec
> Most of the time, the first value is approx. 140 while the second
> value is approx. 18, but I also had this strange 102/8 result. Let me
> add that this wasn't influenced by other processes running at the same
> time.
> Any comments?
> Thanks,
> Edi.

I have no clue what my idebus setting is at other than a dmesg that said 
is was assuming PIO/33.

about this hdparm -tT thing.
I think you will find that if you run it three times in rapid 
succession, the first number is usually junk and the second two are 
somewhat close together.
You might consider something like:
hdparm -tT /dev/hda && hdparm -tT /dev/hda && hdparm -tT /dev/hda
and see what the last two numbers are.  Mine are within +/- 1 at 118/18 

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