Re: FW: Fastest possible UDMA - how?

Re: FW: Fastest possible UDMA - how?

[Manish Lachwani]

Take a look at the drive IDENTIFY data. From the ATA
spec, it can be seen that word# 88 in the IDENTIFY
data can help you find out the UDMA mode selected and
UDMA mode supported. 

The UDMA mode supported is the maximum supported by
the drive. 

Thanks
Manish

> Hi all,
> 
> is it somehow possible to determine what is the
> fastest UDMA-Mode my 
> IDE-Controller supports - independant of the
> chipset?
> 
> Thanks,
>   Michael
> 
> 
> 
> -
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Re: FW: Fastest possible UDMA - how?

[Valdis.Kletnieks]

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On Fri, 10 Jan 2003 11:04:03 PST, Manish Lachwani <m_lachwani@yahoo.com>  said:
> Take a look at the drive IDENTIFY data. From the ATA
> spec, it can be seen that word# 88 in the IDENTIFY
> data can help you find out the UDMA mode selected and
> UDMA mode supported. 
> 
> The UDMA mode supported is the maximum supported by
> the drive. 

Will this DTRT if the IDE *controller* does UDMA-5 but the drives are UDMA-2
at best?

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Re: FW: Fastest possible UDMA - how?

[Manish Lachwani]

If the drives support UDMA 2, then the controller will
operate in UDMA 2. In that case, the IDENTIFY
information will show UDMA 2 for UDMA mode selected
and UDMA 2 for UDMA mode supported.

Now, say that I have a drive that supports UDMA 6 and
the controller supports UDMA 5. Then, from the
IDENTIFY information, the UDMA selected would be UDMA
5 while the UDMA supported would be UDMA 6.

Thanks
manish
--- Valdis.Kletnieks@vt.edu wrote:
> On Fri, 10 Jan 2003 11:04:03 PST, Manish Lachwani
> <m_lachwani@yahoo.com>  said:
> > Take a look at the drive IDENTIFY data. From the
> ATA
> > spec, it can be seen that word# 88 in the IDENTIFY
> > data can help you find out the UDMA mode selected
> and
> > UDMA mode supported. 
> > 
> > The UDMA mode supported is the maximum supported
> by
> > the drive. 
> 
> Will this DTRT if the IDE *controller* does UDMA-5
> but the drives are UDMA-2
> at best?
> 

> ATTACHMENT part 2 application/pgp-signature 



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Re: FW: Fastest possible UDMA - how?

[Michael Knigge]

> Not always true. There are a wide number of cases where the
> UDMA mode being used is not the highest one the drive
> or controller supports. The most simple example is if we
> decide the cabling is not suitable for UDMA66 and higher.

Thank you all for your support.... 

Bye
  Michael

Re: FW: Fastest possible UDMA - how?

[Valdis.Kletnieks]

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On Fri, 10 Jan 2003 11:27:27 PST, Manish Lachwani said:
> If the drives support UDMA 2, then the controller will
> operate in UDMA 2. In that case, the IDENTIFY
> information will show UDMA 2 for UDMA mode selected
> and UDMA 2 for UDMA mode supported.

Which totally fails to tell you that the controller *SUPPORTS* udma-5.



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Re: FW: Fastest possible UDMA - how?

[Alan Cox]

On Fri, 2003-01-10 at 19:04, Manish Lachwani wrote:
> Take a look at the drive IDENTIFY data. From the ATA
> spec, it can be seen that word# 88 in the IDENTIFY
> data can help you find out the UDMA mode selected and
> UDMA mode supported. 
> 
> The UDMA mode supported is the maximum supported by
> the drive. 

Not always true. There are a wide number of cases where the
UDMA mode being used is not the highest one the drive 
or controller supports. The most simple example is if we 
decide the cabling is not suitable for UDMA66 and higher.

Re: FW: Fastest possible UDMA - how?

[Andre Hedrick]

I guess if Google can publish their patches to the driver they ship,
Zambeel should consider publishing the known changes they ship with
products.  Zambeel should decide if it is going to contribute or just
take.

Cheers,

Andre Hedrick
LAD Storage Consulting Group

On Fri, 10 Jan 2003, Manish Lachwani wrote:

> Take a look at the drive IDENTIFY data. From the ATA
> spec, it can be seen that word# 88 in the IDENTIFY
> data can help you find out the UDMA mode selected and
> UDMA mode supported. 
> 
> The UDMA mode supported is the maximum supported by
> the drive. 
> 
> Thanks
> Manish
> 
> > Hi all,
> > 
> > is it somehow possible to determine what is the
> > fastest UDMA-Mode my 
> > IDE-Controller supports - independant of the
> > chipset?
> > 
> > Thanks,
> >   Michael
> > 
> > 
> > 
> > -
> > To unsubscribe from this list: send the line
> > "unsubscribe linux-kernel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at 
> > http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/
> > 
> 
> 
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