Running a 64-bit SCSI card in a 32-bit slot

[phomenter]

How much performance loss am I getting by running a 64-bit PCI card in 32-bit mode? Right now I'm running my Ultra 160 Adaptec SCSI card in this mode and I'm wondering if I'm getting reduced
transfer rates to my hard drive as a result of this. What exactly slows down by running it in 32-bit mode?

Thanks,
Marlin Liew

 

[Radboy]

not 'slowing down' per se .. card still runs at same mhz (speed).

32-bit (33mhz) pci max'es out at 133MB/s (somebody correct me if i'm wrong). i heard actual, realistic data x-fer rate is more like 100. so you x-fer to pci bus (total, from everything) prolly max'es ~100MB/s.

but how much of that is allocated to the SCSI bus depends on ur system specifics & how u use ur pc (ur sound card might want some of that, or ur network card .. if your streaming mp3's, for example)

but even the fastest drive on the planet (x15) can not sustain even 50MB/s .. so, ur really not losing anything.

that's also why U2W/LVD cards (max out at 80MB/s) are not a bad buy (bang for buck - retail tekram u2w can be had for us$120 w/ all cables & terminators)

 

[XeonTux]

probably not that much really

160 is burst and you are never going to get 160 sustained - this is not limited by card->socket its from drive->card

 

[kombatmud]

You wouldn't see a difference unless you had several U160 hard drives. If you do, you would get a minimal increase from the 64 bit PCI slot. 64 bit is much better for multi-channel cards which can really use up the 266MB/sec 66MHz bus speed. The best thing about the 29160 in a 64 bit is the good feeling you get from putting it in =).