Welcome, Guest. Please login or register.

Author Topic: CSPPC and Mixing UltraWide and Fast Scsi Devices  (Read 1185 times)

Description:

0 Members and 1 Guest are viewing this topic.

Offline ReflexTopic starter

  • Full Member
  • ***
  • Join Date: Mar 2005
  • Posts: 123
    • Show only replies by Reflex
CSPPC and Mixing UltraWide and Fast Scsi Devices
« on: December 14, 2018, 08:07:57 PM »
Hello,

I have a quite expanded Amiga 4000 with a PPC and a lot of drives.

Here there is my chain:

- Termination
- Controller
- Quantum Atlas 9GB HD
- Fujitsu 76GB HD
- Acard 7730A with 120GB Sata SSD
- 68=> 50 pin adapter wit upper bites termination
- Iomega ZIP 100
- Iomega JAZ 2GB
- Sony 40X CD-ROM
- Yamaha 4x4x16 CD-Burner

The hard drive will be unmounted as soon as I copy everything on the SATA hard drive, i bought it as the other hard drives are way too noisy.

Anyway I read somewhere that mixing UW devices with SCSI-2 ones will slow down the whole chain to 10 mb/s speed, but this doesn't happen with UltraScsi ones.

But How can i understand what of my devices are SCSI-2, Fast Scsi or Ultra SCSI?

I guess that the iomega Jaz is an Ultra Scsi device but what about all the other ones?

Moreover will a Fast SCSI device slow down the whole chain too?

Any suggestion/advice is welcome.
 

Offline AmigaHope

  • Newbie
  • *
  • Join Date: Dec 2006
  • Posts: 41
    • Show only replies by AmigaHope
Re: CSPPC and Mixing UltraWide and Fast Scsi Devices
« Reply #1 on: December 15, 2018, 03:46:18 AM »
It's been a long time, but if I recall correctly, you cannot mix pre-Ultra2 devices with Ultra2 and up -- this includes Fast, as they use a different electrical signalling on the bus, whereas Ultra2 and Ultra160 devices can play nicely with each other. You can freely mix narrow and wide devices as long as you segregate that end of the bus, terminate the high lines there, and chain all the narrow devices from there on. You still are limited to the fastest compatible signalling rate on the whole bus though.

i.e. Ultra2 and Ultra160 use LVD which you can't mix with SE Fast SCSI and regular Ultra. Some chipsets will let you mix Fast and regular Ultra, but I'm not sure which. I also think you have to segregate old fashioned SCSI-2 to its own bus (and to be honest it's so slow you might as well stick it on an old A2091 or something)

I also seem to remember that there was a tool on the CSPPC SCSI Tools disk that let you see what the actual negotiated speeds were (or they were even viewable in the ESC-key early startup menu on newer CSPPC firmware revisions).

In real life I never got better performance than 20Mbytes/sec or so anyway even off a nice 15Krpm Ultra320 drive running in Ultra160 mode. The 68060 became the limiting factor in how fast the OS could service the DMA buffers. Running AmigaOS 4.1 might give more of a benefit.
 

Offline ReflexTopic starter

  • Full Member
  • ***
  • Join Date: Mar 2005
  • Posts: 123
    • Show only replies by Reflex
Re: CSPPC and Mixing UltraWide and Fast Scsi Devices
« Reply #2 on: December 18, 2018, 12:49:06 PM »
In real life I never got better performance than 20Mbytes/sec or so anyway even off a nice 15Krpm Ultra320 drive running in Ultra160 mode. The 68060 became the limiting factor in how fast the OS could service the DMA buffers. Running AmigaOS 4.1 might give more of a benefit.

I used Unit control, tried to switch all the devices to Synchronous mode and it worked for all but the Zip-100 one.
Indeed this one cannot be switched to Syncronous mode at all neither selecthin this on the early startup menu...

As it's a slow drive I'm considering to take an IDE one.

Anyway can you suggest me a reliable speed benchmark? I use SCSIbench and DiskMonTools but they both don't seem to be very realiable.