Member Avatar for alc6379

Okay, so I bought a SCSI hard drive for an old system, I got it, and it turned out not to be Ultra Wide like they said it would be, but it was Ultra 160LVD. Now, this isn't a problem, because I've got a terminator and everything to make it work with my Ultra Wide system, but here's the kicker:

It's actually really nice for what it is-- it's a 10000RPM Ultra 160 drive, so it's bound to be pretty fast. I'm thinking of instead of dropping it in my old box, I can actually use this as a boot volume for my drive. But, the problem is, my old system has an Ultra Wide card, but my new system doesn't have an Ultra160 controller.

I've been eBaying, Googling, Froogling, and Newegging it, and I'm finding a couple of things. Firstly, Ultra160 adapters are most commonly 64-bit PCI cards. I've found some that say 64/32-bit, and one or two that are just 32-bit PCI cards. My question is this: Can I plug a 64-bit card into a 32-bit slot and have it work? The interface on the cards look like they'd fit, with the exception of the extra row of connectors on the back that would fit in a 64-bit slot.

Now, there's an additional part to this, too: I've found a 32-bit Ultra160 card that's reasonably priced, and I'm thinking of getting it. Can anybody estimate what kind of speed impact I can expect, if any, by not running a 64-bit card in a 64-bit slot?

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Dani AI

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Good follow-up to and nice pointer from . There are three separate things to check before buying: mechanical fit/voltage keying, electrical signalling, and bus bandwidth. Many 64‑bit cards are shaped so the front (32‑bit) portion will seat in a 32‑bit slot, but some server cards are 3.3V‑only and won’t physically or electrically mate with older 5V‑only slots — verify the vendor spec or look for the 3.3V notch on the card edge.

On performance: a 32‑bit/33MHz PCI slot is limited to roughly 133 MB/s; a full 64‑bit/66MHz installation delivers several hundred MB/s (roughly 4x the 32/33MHz rate). A single 10k SCSI disk rarely sustains anywhere near the 133 MB/s cap, so for one fast boot drive a 32‑bit Ultra160 card will usually be fine. Where you’ll hit limits is with multiple drives or RAID arrays that generate concurrent throughput.

SCSI-specific points to watch: to get full Ultra160 LVD speeds the controller, all devices and cables must be LVD — mixing in single‑ended devices forces the bus into slower SE mode. Use proper LVD cables/termination, update controller firmware and drivers, and confirm the card’s SCSI BIOS supports booting if you want it as a system volume.

Practical recommendation: if cost is the deciding factor and this is only for a single boot disk, the inexpensive 32‑bit Ultra160 card is a sensible buy. If you plan expansion, heavy IO, or RAID, invest in a true 64‑bit/66MHz (or PCI‑X) controller and make sure the motherboard and drivers support it.

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Member Avatar for jifiii

I think they are backwards compatible, but do not hold me to that. But if you put a 32-bit card into a 64-bit slot, it will only have a 32-bit Bus.

Member Avatar for alc6379

Okay, I found it out.

If you look at a 64-bit PCI card, it's keyed up front like a 32-bit card. If you plug a 64-bit card into a 32-bit slot, it should just run at 32-bit.

/me runs off to get a less expensive SCSI card!

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