Any SCSI (computer related) experts out there?!

[TheRic]

Looking for some help with the SCSI devices on my home computer. I recently noticed that everything is running at 40MB/s. I thought the CDRW was dragging things down, so I unplugged it (and the Tape Drive). Same results. I tried several different cables, tried only one hard drive attached, etc. It always comes up with 40MB/s.

My MB is rated at 80 MB/s (Adaptec 7890 Ultra2 SCSI), I just added an Adaptec 29160 (160MB/s) PCI controller card. Wanted to split the drives (320MB/s) from the Tape Drive (80MB/s) and CDRW (40MB/s ). This is when I noticed the problem.

The SCSI cables 68pin LVD with active termination. I don’t know the ratings on the cables for sure but I thought they were rated for 160MB/s or 320MB/s, I would think they should be at least rated at 80MB/s (don’t think 68pin LVD cables come lower than 80MB/s).

Where I’m talking about the speed is when the SCSI controller finds the device, so this is before OS. If I go into the SCSI card setup it shows it is set for 80MB/s (or 160MB/s depending on which controller card I go into for each device.

Any clues on what might be going wrong?

[cgallery]

Kinda hard to know w/o doing some more testing. If I had the machine here I'd: (1) Make sure my SCSI cards all had the latest firmware. (2) Try a different cable/terminator (your cable is twisted pair and the terminator is active, right?). (3) If all else fails, try a different make/model of hard drive to eliminate compatibility issues.

[TheRic]

cgallery thanks for the quick response.
1) Not 100% sure on this, would think the 29160 controller would at least see 80MB/s even without the latest firmware (so I didn't check on this). Having trouble finding anything on firmware for the on board controller. It does have the latest BIOS loaded, thought about reflashing it just to make sure.

2) Have tried 3 different cables. Yes on twisted and active termination.

3) Three different brand hard drives. Have tried them one at a time to help isolate things, same results.

Any suggestions on what to test?

[Rand]

I poked around on the adaptec website and found this:

The Ultra160 specification has no provisions for narrow 25 or 50 pin (8 bit) devices. The Ultra 160 specification only supports wide 68 pin (16 bit) devices.
The Ultra2 specification did have a provision for devices. The Ultra160 SCSI card is falling back to Ultra2 narrow operation (that is, 40 MB/sec) when you disable the "Initiate Wide Negotiation" switch
-------------------------------------------------------
Try enabling "Initiate Wide Negotiation"

Let me know if that helps,
Rand

[TheRic]

Rand, "Initiate Wide Negotiation" is enabled on both devices.

Also let me clarify that when I tried only 1 hard drive (320 MB/s rating) on 1 SCSI controller I had the PCI controller removed or the on board SCSI controller disabled. I will admit that I did NOT try every combination of cable, hard drive, SCSI controller, but willing to bet I hit most of them . I'm normally pretty thorough at testing options / isolating problems, OK some people would say anal.

[gwyneth]

You probably checked this, but...

What about the combination of BIOS settings and those in the system settings that determine whether and how those are used (some of which are not in the obvious place to find them)?

[TheRic]

You probably checked this, but...

What about the combination of BIOS settings and those in the system settings that determine whether and how those are used (some of which are not in the obvious place to find them)?

Not sure what you are refereeing to. If you are talking "system settings" as in OS system then, let me state that this problem is happening before I even get to the OS.

If you are talking firmware for the MB then I have not been able to find any firmware updates for this motherboard (It is more than several years old, maxed out with 2 PIII 1000MHZ cpu's).

[sparkeyjames]

This is a problem with SCSI busses. They will fall back to the buss speed of the slowest device on the chain. One way around this problem is to get a dual channel SCSI interface card ( I have one with a tape drive on one channel and HD's on the other). Put the slow devices on one channel and the faster devices on the other.
I should point out one bad fact. Not all SCSI device formats are compatible so if you upgrade to a new card you might have to reformat. That is to say the buss specs are the same but how they deal with the data and it's organization on said device may be different. SCSI is a buss specification for data transfer not a physical disk organization spec.