Please explain Scsi 64-bit pci in a 32-bit pci slot

[gonzo2k]

Does my 29160 adaptec scsi host peak at ultra2 (80mb/sec) or higher with a LVD160 HD. Any AMD boards with a 64-bit pci slot or two? I'm going to keep my 2940U2W if 80mb/sec is all I can get from the LVD160 card.

 

[Demon-Xanth]

The Tyan K7 Tiger and Thunder boards have 64bit PCI. But when used in a 32 bit slot it's like the 8 and 16 bit ISA cards/slots. The extra connection can just be ignored. You will still do the Ultra160 speeds and drives can transfer data between eachother at the full speed if the PCI bus is not involved. 32/33 PCI can do 133MB/sec.

What slot the card is in has no effect on what the drives talk to the card at. They are isolated protocols.

 

[samgau]

You get 64bit pci slots in Intel and serverworks boards... I have not heard of AMD boards supporting that... seems to me that the AGP slot is and evolution of the 66Mhz 64bit PCI... anyway I diverge...
the limiting factor is your HD not your card,pci slot, or transfer medium(68pin U2 LVD). The max transfer rate on a pci slot is 133MBytes/s so you are safe there and the U160 is rated for 160 MBytes/s... but I don't think the HD's can reach that high of a transfer rate...
As for the card working in a 32 bit slot compared to a 64 bit slot... i guess they just made it backwards compatible for boards that don't have 64bit pci slots...

editI stand corrected... some other boards do have 64bit pci slots

 

[Demon-Xanth]

AGP isn't really an evolution of 66/64PCI. AGP is a port and not a bus. Being a port AGP requires no arbitration or ID to decide which device gets what data. There's just one. (then add in all the add ons since AGP 1x)

 

[gonzo2k]

thanks for your reponses folks!!!