Re: Question with AHCI and (UDMA/100 vs. UDMA/133)

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Hello.

Justin Piszcz wrote:

> Do some chipsets (SiI 3132 vs. Intel ICH9) run certain drives at 
> UDMA/100 vs. UDMA/133?

   Intel ICH chipsets never supported UDMA/133.

> I have several 750GB WD drives (exact make/model) and the ones on the 
> intel chipset show up as:
>
> [    1.407321] ata3.00: ATA-7: WDC WD7500AAKS-00RBA0, 30.04G30, max 
> UDMA/133
> [    1.407409] ata3.00: 1465149168 sectors, multi 0: LBA48 NCQ (depth 
> 31/32)
> [    1.408300] ata3.00: configured for UDMA/133

   I'm *very* surprised to see that on ICH9. Oh wait, that's SATA 
controller, not PATA! Then I don't know...

> The ones on the SiI 3132 chipset show up as:
>
> [    9.604413] ata11: SATA link up 3.0 Gbps (SStatus 123 SControl 0)
> [    9.619024] ata11.00: ATA-7: WDC WD7500AAKS-00RBA0, 30.04G30, max 
> UDMA/133
> [    9.619111] ata11.00: 1465149168 sectors, multi 16: LBA48 NCQ 
> (depth 31/32)
> [    9.620029] ata11.00: configured for UDMA/100
>
> If they are both 3.0 Gbps, are they both the same speed even though 
> one is configured for a slower speed than the other?

   I'd think so.

> Or is it the case that the SiI 3132 does not support AHCI and that is 
> the reason for the difference?  Does it make any difference in 
> performance?

   Hardly -- if these are true SATA controllers.

MBR, Sergei