I found a picture of a prototype
9150 logicboard and it seems to have a 53C
F96 NCR chip so Fast-SCSI-2 should be supported from the get go.
View attachment 33667
From the "Clarification on the Quadra 950's SCSI bus"-Thread:
I can't find any documentation on the Atto, what are the expected transfer speeds on that 50 pin internal connector? Asking for a friend (aka I may have found one locally).
Any idea?
@trag ?
@ArmorAlley ?
Pretty sure the Atto is 10MB/s on the narrow connector and 20MB/s on the two Wide connectors.
SEIV uses the Qlogic ISP1000 chip and that's what it supports. The 1000U supports UltraSCSI, but I'm looking at an SEIV right now and it has the 1000, not the 1000U. Bit of luck, I happened to have the box down from the attic that has my SEIV in it.
BTW, if you could find those XC3030As and the ISP1000 I don't see anything on that board that would make reproducing it difficult.
Regarding the photo and discussion from "Clarification of the Q950" thread:
That's a photo of a 9150 prototype. The earlier discussion was of the Q950. I'm not sure what information or idea you're trying to convey -- which is a request for clarification, not a criticism.
The 9150 does support Fast narrow SCSI (10 MB/s) on one of its two SCSI busses. As does the 8100. The 8100 and 9150 used the 53CF96 for their internal-only Fast SCSI bus.
When Apple introduced the PCI PowerMacs with exactly the same SCSI arrangement as the NuBus PowerMacs, they switched from the 53CF96 to the MESH chip. Which is what leads me to suspect that MESH may be nothing more than a licensed (or illicitly copied?) 53CF96.
If one is good with software, it might be interesting to dig the drivers for each (MESH, 53CF95) out of their respective ROMs (PCI PowerMac, NuBus PowerMac) and see how they differ, if at all. I guess the Linux-porting folks might have some insight.
The Q950 stuck with the 53C96, which limited it to regular 5 MB/s speeds.
Perhaps the point is that unless you get a Fast and
Wide drive the SEIV isn't going to provide a lot of improvement over the Internal SCSI bus?
One of the most important things you can do for performance on these old machines is get a more modern SCSI hard drive -- well, more modern than when they were released.
While Fast & Wide SCSI interfaces (20 MB/s) were available in the early/mid '90s, hard drives could not deliver better than about 6 MB/s until some time past the mid 90s.
I had a small collection of ST32550 Seagate hard drives. These were the beginning of the Barracuda line and some of the first drives to spin at 7200 RPM. But in testing, I could never get better than 6MB/s out of them. Other drives were slower, but why did my ST32550W have a Fast & Wide interface if the drive platters couldn't even deliver 10MB/s, never mind 20 MB/s?
I had an FWB Jackhammer in my Power 120 (PM8100 clone from PowerComputing) and a copy of RAID Tool Kit.
When I put four Fast & Wide (20 MB/s) ST32550W drives on the JackHammer in a striped RAID, I got about 8 MB/s.
A little experimenting and I found going beyond 2 drives really wasn't getting me any improvement.
But I left 2 drives on the JackHammer and put an ST32550N (Fast SCSI, 10 MB/s) on the Internal Fast bus and then included that in the RAID and that got me up to 10 MB/s. I think I also put one drive on the internal/external SCSI-2 (5 MB/s) bus and that got me up to 12 MB/s for the RAID.
I may be misremembering the details a little, (details were posted in the PowerWatch forums which are long gone) but the lessons were, hard drives of the day don't deliver data as fast as the electronic interface can move it. And the various inputs on the computer are bandwidth limited too.
It'd be interesting to retry those experiments with a SCSI drive from the late 2000s that can deliver ~30 - 60 MB/s and also with an SEIV instead of the JackHammer.
I stuck with JackHammer mainly, because IIRC, the JackHammer was compatible with the NewerTech G3 upgrades and the SEIV wasn't. Although I never did add a G3 to the Power120. I can't remember if Sonnet ever cracked compatibility with the SEIV for their G3 upgrades. Sonnet was usually far behind and less compatible than NewerTech. Screwy universe that they ended up being more successful in the long run.