Maximum SiliconExpress IV Throughput

[eharmon]

Continuing my SiliconExpress experimentation, I've been doing some benchmarks on my Quadra 650 board with ZuluSCSI.

Read

Native SCSI	ZuluSCSI (RP2040)	4,700KB/s
SiliconExpress IV (8-bit) - 1.6.5	ZuluSCSI (RP2040)	8,123KB/s
SiliconExpress IV (16-bit) - 1.6.5	ZuluSCSI Wide	8,959KB/s

Write results are generally ~30% slower.

I need to try the SCSI 4.3 firmware to see if it's any different.

Wombat boards have a NuBus implementation that leaves a bit to be desired (no double data rate transfers @ 20MHz except between cards), which TIL 9305 implies should give you 8-10MB/s to the logic board and a theoretical 20MB/s out of the logic board (if the destination device could accept block transfers at zero wait). So that seems ballpark to what we're getting.

Still, surprisingly rough! So it seems on the earlier Quadras there's only a small boost from moving to 16-bit (~10%).

The official documentation always seemed ambiguous to me if later devices really supported 20MHz transfers to the logic board. Has anyone benchmarked a Quadra AV or 6100/7100/8100 and a SiliconExpress?

 

[Unknown_K]

I benched spinning disks ages ago on Jackhammers and SEIV (I have SEII's and other Nubus SCSI cards as well). There should be results from back then on the forum if you search.

 

[lobust]

An interesting data point - unfortunately I didn't document much of it - I did exactly what you've done here a couple of years ago with a SCSI2SD v6. What stands out to me is that I got the same results as you through the SEIV, but my native reads were significantly slower than yours at ~2800

I do have an 840av now and still have the SEIV, but I have little spare time for this kind of thing right now...

Here are my old threads on the topic, someone else posted some Q950 and PM8100 benchmarks in the SEIV one:

ATTO Silicon Express II Nubus

I recently bought one of these to try out - google turns up almost nothing about this card, so I thought I'd document what I've learned about it. 1. It is bootable, at least on a Quadra 650/800, haven't tried any others yet. It will not find a bootable disk on it's own, but if you boot by some...

tinkerdifferent.com

ATTO Silicon Express IV Nubus

I have read some comments here and there suggesting the Silicon Express IV is not bootable. I have just acquired one, and I can confirm that it IS in fact bootable, at least on a Quadra 800, which is the only Mac I have thus far tested it in. The same rules apply as with the SE II - it will...

tinkerdifferent.com

 

[eharmon]

An interesting data point - unfortunately I didn't document much of it - I did exactly what you've done here a couple of years ago with a SCSI2SD v6. What stands out to me is that I got the same results as you through the SEIV, but my native reads were significantly slower than yours at ~2800

I do have an 840av now and still have the SEIV, but I have little spare time for this kind of thing right now...

Here are my old threads on the topic, someone else posted some Q950 and PM8100 benchmarks in the SEIV one:

ATTO Silicon Express II Nubus

I recently bought one of these to try out - google turns up almost nothing about this card, so I thought I'd document what I've learned about it. 1. It is bootable, at least on a Quadra 650/800, haven't tried any others yet. It will not find a bootable disk on it's own, but if you boot by some...

tinkerdifferent.com

ATTO Silicon Express IV Nubus

I have read some comments here and there suggesting the Silicon Express IV is not bootable. I have just acquired one, and I can confirm that it IS in fact bootable, at least on a Quadra 800, which is the only Mac I have thus far tested it in. The same rules apply as with the SE II - it will...

tinkerdifferent.com

Interesting, so from those benchmarks, you can't really break the 10MB/s barrier on an 8100 either. I also noticed the same dip with a PowerPC card in the Quadra.

The RP2040 Zulu is quite a bit faster than the SCSI2SD v6. I wonder if the card's read ahead cache makes up for lower transaction performance, which is why you see a bigger jump on the SCSI2SD.

I want to run three more benchmarks:

• Run the Q650 @ 40MHz. It won't speed NuBus but it will tighten memory performance which might squeak a little more speed out. Doubt it makes much of a difference.
• Switch to the SCSI 4.3 firmware. Theoretically this improves burst performance as we're less bottlenecked on the CPU. Again, I doubt it makes much of a difference, but maybe it brings back PPC perf.
• Assign the card to a Radius Rocket, which should allow direct NuBus 90 transfers. The chip on the SE IV is definitely capable of 20MB/s, so if anything can do it, that should.

 

[zigzagjoe]

Interesting, so from those benchmarks, you can't really break the 10MB/s barrier on an 8100 either. I also noticed the same dip with a PowerPC card in the Quadra.

The RP2040 Zulu is quite a bit faster than the SCSI2SD v6. I wonder if the card's read ahead cache makes up for lower transaction performance, which is why you see a bigger jump on the SCSI2SD.

I want to run three more benchmarks:

• Run the Q650 @ 40MHz. It won't speed NuBus but it will tighten memory performance which might squeak a little more speed out. Doubt it makes much of a difference.
• Switch to the SCSI 4.3 firmware. Theoretically this improves burst performance as we're less bottlenecked on the CPU. Again, I doubt it makes much of a difference, but maybe it brings back PPC perf.
• Assign the card to a Radius Rocket, which should allow direct NuBus 90 transfers. The chip on the SE IV is definitely capable of 20MB/s, so if anything can do it, that should.

The earlier rockets don't support 20mhz transfers; the extra pins to support 2x transfers aren't wired. Rockets all support block transfers and can perform block transfers between cards (even if the host doesn't support block transfers) but it's at the standard 10mhz rate. Maybe the later Stage II Rockets support 2x. You might check the SCSI card too - if those pins aren't wired, then no 2x transfers.

 

[jeremywork]

Not in front of me right now, but I was able to get ~18MB/sec on a Quadra 840AV with a 10kRPM 16-bit drive attached to an SEIV. I think the 8100/100 and 8100/110 will perform within ballpark. The 6100, 7100, and 8100/80 have an older version of the NuBus controller IIRC which may inhibit performance.