On Sun, 2012-03-04 at 14:48 +0100, Jean Delvare wrote: > Hi all, > > After reading > http://en.wikipedia.org/wiki/Parallel_ATA#Features_introduced_with_each_ATA_revision > it seemed clear to me that there was a direct relation between the > operating speed of a (P)ATA hard disk drive and the version of the ATA > standard it implemented. However I see the following in my kernel logs > on an old machine (kernel 2.6.34, Intel ICH5 controller): > > ata1: PATA max UDMA/100 cmd 0xeff0 ctl 0xefe4 bmdma 0xef90 irq 18 > ata2: PATA max UDMA/100 cmd 0xefa8 ctl 0xefe0 bmdma 0xef98 irq 18 > ata2.00: HPA unlocked: 40018511 -> 40020624, native 40020624 > ata2.00: ATA-6: Maxtor 52049H4, DAC10SC0, max UDMA/100 > ata2.00: 40020624 sectors, multi 16: LBA > ata1.00: HPA unlocked: 78175679 -> 78177792, native 78177792 > ata1.00: ATA-5: MAXTOR 6L040J2, A93.0300, max UDMA/133 > ata1.00: 78177792 sectors, multi 16: LBA > > While the second disk matches the wikipedia table (ATA-6 introduced > UDMA/100), the first one doesn't: UDMA/133 wasn't supposed to exist in > standard ATA-5. > > Digging old logs, I also found this (same machine, same kernel, > different drive): > > ata2.00: ATA-4: WDC WD102AA, 05.05B05, max UDMA/66 > > Here again, UDMA/66 wasn't supposed to exist in standard ATA-4. > > Can anyone explain this mystery to me? It's not really a mystery: in this device speed hungry world manufacturers usually get out ahead of standards, particularly for transport and signalling electronics. In SCSI, SCSI-2 only covered 10Mhz cable speeds but we were up to about 40MHz before SCSI-3 finally came along and ratified it (and even then, lots of drives that go up to high ultra speeds still only reported SCSI-2 compliance). In SCSI, we got around this problem eventually by separating the command, device and transport layers into different standards. ATA does this from ATA-8. James -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
