Hmmm dmesg gives out a message about the ide bus defaulting to 33MHz for PIO and everyone with IDE drives starts to wonder, "Am I really getting all that I should out of my drive?" PIO is Programmed Input-Output It has five modes, PIO0-PIO4 33MHz is PIO4 Programmed Input/Output is reading and writing that is overseen by the CPU. In 1996, most cheap PCs did exactly that. Then came DMA or Direct Memory AAccess where the ancillary hardware transferred data to memory and told the processor when it was done, or transferred memory out to disk from a map provided by the processor and again signalled when done--very little processor load on disk transfers--things got faster. So for almost all of you the ide bus speed default for PIO is irrelevant because you don't use it, not even for a CD-ROM, which are almost all DMA these days. Now the PCI (Peripheral Connect Interface) bus is another standard in PCs. Even some MACs use it. It takes 32 bit (or 64-bit on 64-bit processors) data at a rate of 33MHz and provides it to cards plugged into the bus and to the IDE disk drives (and maybe even to SCSI disk drives through a SCSI adapter card plugged into the PCI bus) Some older Motherboards could not independently clock the PCI bus so that when they overclocked the Front side bus to kick the processor, the PCI bus became overclocked as well. Many PCI cards performed well at 41.5MHz, but that is another story. Anyway, the PCI bus runs at 33MHz on most modern PCs. So how does a 100MHz ethernet card or 100MHz IDE transfer happen? On the disk end, it doesn't. No way. You can get about 220MHz out of a 7200 rpm Disk, and that is the rate at which data spins on and off of it. You need on-controller (the little card attached to the disk) memory for transfer to happen at full burst speed, because the 100MHz refers to an 8-bit wide data bus from controller to motherboard. the 220 refers to a 1 bit wide read or write from or to disk, which is less than 30 MHz when divided by 8. OK. Lets look at some bandwidths in terms of bus... PCI 33MHz x 32 bits wide 1,056,000,000 bits/second IDE 100MHz(max) x 8 bts wide 800,000,000 bits/second Ethernet 1 GHz(max) x 1 bit wide 1,000,000,000 bits/second Whoo! The PCI bus will need another protocol to support the coming 10 GHz ethernet cards, or maybe we will need a new bus for them. As you can see the pCI bus is barely able to support 1GHz ethernet cards but should have no trouble with a 100MHz Ether net card or three and a 100MHz hard disk drive. Civileme
Want to buy your Pack or Services from MandrakeSoft? Go to http://www.mandrakestore.com
