while the PCI bus IS slower than the system bus, it is NOT the limiting factor in data transfer to and from the HD. in a sawtooth, the PCI bus speed is 33 MHz and the data path is 64 bits wide. multiply (33,000,000 cycles/s) times (64 bits/cycle), and you get 2112 Mbits/s, and dividing by 8 (bits/byte), you find that the PCI bus has a theoretical limit of 264 MB/s data transfer rate. in reality it is somewhat slower, but even if we take a conservative estimate of 80% of the theoretical max, that's still 211 MB/s. that is way faster than the controller interface. but the controller interface is STILL not the limiting factor. there is no single HD in existence that can get anywhere near that, and if we are talking about a drive of the same vintage as the sawtooth in the original post, the chances are good that it is somewhere around 5-10 MB/s sustained internal transfer rate, and definitely not more than 25-30 MB/s sustained internal transfer rate. the most modern, most expensive, SATA drives are just reaching 60 MB/s internal transfer rates, and the best IDE (PATA) or Ultra3 SCSI-LVD drives i have ever tested are about 40-50 MB/s.
so, ONCE AGAIN, to sum it up, NONE of the busses OR controller interfaces are the limiting factor, when considering a single HD connected to either a PCI controller OR the onboard controller. the HD itself is the limiting factor. is any of this getting thru? On Sep 18, 3:36 pm, John Niven <[email protected]> wrote: > > So to sum up, the 100MHz system (and memory bus) bandwidth is NOT the > limiting factor for a scsi disk connected via a PCI card, it is the PCI bus > speed. > > This same limitation applies to all other pci connected disk systems. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list -~----------~----~----~----~------~----~------~--~---
