Why would drive run at UDMA33? (Segate 80GB)

paul beard paulbeard at mac.com
Sun Dec 7 22:20:56 PST 2003

On Dec 7, 2003, at 10:07 PM, JacobRhoden wrote:

> I typed 'man atacontrol' and it didnt seem to help! (grin). Seriously, 
> i had a
> look and worked out how to list/display the modes of drives,  and i am 
> not
> sure what commands i would type to help fix the speed?

      mode     Without the two mode arguments, the current transfer 
modes of
               both devices are printed.  If the mode arguments are 
given, the
               ATA driver is asked to change the transfer modes to those 
               The ATA driver will reject modes that are not supported 
by the
               hardware.  Modes are given like ``PIO3'', ``udma2'',
               ``udma100'', case does not matter.  If one of the devices 
               should not be changed, use a nonexisting mode as argument 
               ``XXX''), and the mode will remain unchanged.

               Currently supported modes are: BIOSDMA, PIO0 (alias 
               PIO1, PIO2, PIO3, PIO4, WDMA2, UDMA2 (alias UDMA33), UDMA4
               (alias UDMA66), UDMA5 (alias UDMA100) and UDMA6 (alias 

So you can type 'atacontrol mode <channel> <mode where mode is one of 
the options listed>' and change the speed, at some potential risk, as 
the man page warns.

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