On Wednesday 24 April 2002 02:12 pm, Jay wrote:
> This is what it says....
>
> ide: Assuming 33MHz system bus speed for PIO modes; override with
> idebus=xx VP_IDE: VIA vt82c686b (rev 40) IDE UDMA100 controller on
> pci00:07.1 ide0: BM-DMA at 0xd000-0xd007, BIOS settings: hda:DMA,
> hdb:pio ide1: BM-DMA at 0xd008-0xd00f, BIOS settings: hdc:pio,
> hdd:pio hda: MAXTOR 6L020L1, ATA DISK drive
> ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
> hda: 40132503 sectors (20548 MB) w/1819KiB Cache, CHS=2498/255/63,
> UDMA(33)
>
>
> -Jay
/usr/src/linux-<kernel_version>/Documentation/ide.txt
"idebus=xx" : inform IDE driver of VESA/PCI bus speed in MHz, where
"xx" is between 20 and 66 inclusive, used when tuning chipset PIO
modes. For PCI bus, 25 is correct for a P75 system, 30 is correct for
P90,P120,P180 systems, and 33 is used for P100,P133,P166 systems. If in
doubt, use idebus=33 for PCI. As for VLB, it is safest to not specify
it. Bigger values are safer than smaller ones."
PCI bus speed in MHz for anything >= to a 100mhz FSB (front side
bus) cpu is 33 mhz. idebus= is the speed of the PCI bus, not the HDD
mode (as Charles correctly also said). All ata/33,66,100, or 133
drives run on the 33mhz PCI bus. For a 100mhz FSB processor, it's
100/3 to get the PCI clock, for 133mhz FSB, it's 133/4. So the PCI
bus is always 33. As the doc says, setting it higher won't hurt, it'll
just be ignored.
--
Tom Brinkman Corpus Christi, Texas
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