Tom Brinkman wrote: > > > /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. > >
This thread amply demonstrates my frequently stated contentions about the life of a thread: it changes so radically that it ends up being about something that is was never intended to be about (can you follow that?). The original posted stated he was having trouble getting his harddrive to function at the expected UDMA 100 speed. He made these statements based on his obervations while running "hdparm" tests on his harddrive. He did not talk about PCI bus speed on the mobo. He did not mention anything about FSB. All this has been added by others who confused the issues because they did not understand the difference between these two elements. The original poster is right: you can have a ATA 100 harddrive with the appropriate IDE cable, and a chipset that supports ATA 100, such as KT266, and Linux-Mandrake 8.2 will *always* load it as UDMA 2. The only help I saw, for the original poster who wanted UDMA 100 to be set on his harddive, was made by the individual that suggested that the person should upgrade his kernel version. I wonder if someone could comment *specifically* on this situation... Dr John Craig Woods UNIX SA
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