Re: FUD or FACTS ?? but a new FLAME!

[Vojtech Pavlik]

On Mon, Jun 03, 2002 at 07:36:35AM +0200, Martin Dalecki wrote:

> I have been reading the stuff about the difference between ATA/100 and
> ATA/133 talking about clock cycles, buffer sizes, transmission directions
> and what not and were quite unable to understand what the point was until I
> looked at the public Intel ICH4 spec (the one available to us mortals
> without connections :-)
> 
> ftp://download.intel.com/design/chipsets/manuals/29860002.pdf

Thanks for the pointer, I was unable to find it when I was assing ICH4
support - and most board-maker sites at that time advertised ATA-133.

> Intel do state that the ICH4/82801DB supports only ATA/100 not ATA/133.
> Looking through some reviews on the net on the 845E/G they do say the same
> thing.

Actually, it doesn't support ATA-100 correctly either. It has a 133MHz
base clock, and for ATA-100 uses a 3 clock cycle. 133MHz/3*2byte = 88.6 MB/sec.

So the maximum documented speed on ICH chips is 88.6 write, and 100.0
read - because there the drive dictates the speed.

> In the light of that perhaps the code in drivers/ide/piix.c stating that the
> ICH4 does ATA/133 is a bit optimistic and should be moved to the "try it if
> you want to " CONFIG_BLK_DEV_PIIX_TRY133 option.

Agreed. Martin, please do that. Also, please change the Config.in
comment to something like "Enable undocumented ATA-133 on ICH chips",
or somehting alike..

> Of course Vojtek might have better info that says otherwise.

No, I don't. ICH4 was designed to have ATA-133 capability, Intel
probably downgraded that in the spec because of some problems.

-- 
Vojtech Pavlik
SuSE Labs