In theory, the old PCI bus has a 132MByte/s transfer speed.
but the pci bus is a parallel bus. so all the devices on the pci bus share that max speed. and then there's also overhead due to addressing, selecting device etc... limiting the max transfer further.
that aside.

The Ultra 320 scsi bus is an annoying piece of history due to it being limited to only four devices on the bus somehow. frequencies, reflections...
I've never gotten more devices working at U320 speeds at the same time with the limited hardware I got.

While the scsi bios may say that everything is ok, the OS & driver might be running a slower speed. windows is so much fun giving all the information freely /s
Testing with a linux dist can give more insight, and doing a disk cache speed read test (ie from drive cache to system memory) should get you an indication on where the bottleneck is. hdparm -tT i think.
Though depending on the dist it could false results as well due to it not really doing the drive but the system cache, argh.

Some more details about the machine you're testing this on would be nice as well

Tested on 2 different Intel systems so far.
My trusty test-bench P3B-F with an 1.1GHz P3, just AGP graphics and the SCSI card attached and not sharing IRQ.
And my awesome Intel L440GX+, sporting a maxed out 2x600MHz Katmais and 2GB ECC (with an almost but definitely not a PCI-X slot, proprietary cr*p!).

And also working on getting my only PCI-X MB to cooperate.
Its the notoriously picky early model A7M266-D.

bofh.fromhell wrote on 2023-03-03, 13:58:

So after many years of keeping an eye out for some affordable fast SCSI drives i finally struck gold. A bunch of 10k and 15k dri […]
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So after many years of keeping an eye out for some affordable fast SCSI drives i finally struck gold.
A bunch of 10k and 15k drives were included in some other random (and not interesting HW), and all but one works just fine (!).
They are mostly HP branded Quantum and Seagate drives, but also a few non OEM of the same brands and all between 18 and 36GB.
Most impressive are the 15k drives, which are not only lightning fast but also very quiet.

Now to the "problem".
They all cap out at a max transfer rate of just shy of 80MB/s.
I know that for some of the drives this is close to what they can manage.
But for many of them its a clear bottleneck.
The only SCSI card i have that's capable of >80MB/s is an Adaptec 29320A (PCI-X).
Most of the drives claim "Ultra 320 SCSI", and nothing in the cards setup suggests that there's anything preventing a 320 rate.
The card helpfully tells you what criteria needs to be met to reach 160 or 320, and it all checks out.

Now I'm only (for now) running the card in a regular PCI slot, but surely that should not force the card to limit drive speeds?
And even with overhead regular PCI should reach well over 100MB/s, right?

Doing my testing with Atto and HD-tune.
And i have tried various cables and terminators.
Everything works just fine and feels extremely snappy, its just the max transfers that are clearly capped ......

Clearly I'm missing something here.

Pls give us a motherboard, SCSI-card and configuration with pictures

bofh.fromhell wrote on 2023-03-03, 14:43:

Tested on 2 different Intel systems so far. My trusty test-bench P3B-F with an 1.1GHz P3, just AGP graphics and the SCSI card at […]
Show full quote

Tested on 2 different Intel systems so far.
My trusty test-bench P3B-F with an 1.1GHz P3, just AGP graphics and the SCSI card attached and not sharing IRQ.
And my awesome Intel L440GX+, sporting a maxed out 2x600MHz Katmais and 2GB ECC (with an almost but definitely not a PCI-X slot, proprietary cr*p!).

And also working on getting my only PCI-X MB to cooperate.
Its the notoriously picky early model A7M266-D.

HA! You need a PCI-X (PCI64 with 66Mhz) slot and SCSI-card for max. speed of your SCSI subsystem.

Babasha wrote on 2023-03-03, 14:49:

bofh.fromhell wrote on 2023-03-03, 14:43:

Tested on 2 different Intel systems so far. My trusty test-bench P3B-F with an 1.1GHz P3, just AGP graphics and the SCSI card at […]
Show full quote

Tested on 2 different Intel systems so far.
My trusty test-bench P3B-F with an 1.1GHz P3, just AGP graphics and the SCSI card attached and not sharing IRQ.
And my awesome Intel L440GX+, sporting a maxed out 2x600MHz Katmais and 2GB ECC (with an almost but definitely not a PCI-X slot, proprietary cr*p!).

And also working on getting my only PCI-X MB to cooperate.
Its the notoriously picky early model A7M266-D.

HA! You need a PCI-X (PCI64 with 66Mhz) slot and SCSI-card for max. speed of your SCSI subsystem.

Well yes, I'm well aware of the limitations of standard PCI =)
But surely the card won't limit itself to 80MB/s just because its connected to normal PCI?
Anyways, I'll try and get my uncooperative A7M266-D to play along.

Never take in my hand dual Athlon motherboard. Carefully read manual - sometimes there “nice” PCI-X limitations, like do not mix PCI-32 and PCI-64 card or cards with 33 or 66MHz bus.

Well problems solved.
Both the Mobo and the speed:

Mobo problems were mostly solved with a beefier PSU, or atleast a stronger +5v.
Supposedly it pulls CPU power from both +12v and +5v, but clearly theres a lot of load on +5v cause 20A was not enough.

And disk speeds were instantly normal once the card was in a PCI-X slot.
I really did not think that was the issue, clearly the card limits itself in a "normal" PCI slot.

Well the more you know!

what do you get on the P3B-F ?

kreats wrote on 2023-03-04, 15:19:

what do you get on the P3B-F ?

Just shy of 80MB/s both max transfers, the line in HD-Tune goes completely flat, and burst rates.

I get about 60MB/s with 39160 and p3b-f, but I use 2.5 savvio with SCA adapters because I can't take the noise of faster SCSI drives.

There are other of reasons to prefer SCSI though apart from raw speed. You get a lot more drives and external options.