Low SCSI 3 transfer rates

I have an Adaptec 29160 U160 SCSI card with a new Cheetah U160 15k hard drive.
I was using wrong, non Lvd cable at first and later learned that the controller would step down to SE mode when not using a LVD terminated cable.
I got this cable today and out of curiosity I measured the transfer rates with both cables. According to the Adaptec SCSI bench program, I am getting around 40K Kbytes per second with either cable. I am startled. Shouldn't I get a much better transfer rate with the new LVD cable, since now the drive is supposed to run in U160 mode?.
Who can help me here? How can I find out if the drive is running in SE or LVD mode and why do I get the same transfer rates?
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  1. All I can offer you is my own experience on your question and by no means say I am an expert. I had the same delema when I installed my U3 Hard disks, was thinking wtf!
    Anyway that’s 40Mb/s through the PCI bus I think, my IBM's run at 36MB/s according to HD tach and burst's at 80Mb/s due to my mobo's 32bit/33mhz PCI bus. From what I understand I can improve those figures by upgrading to a board with 64bit/66mhz PCI card slots.

    I have the same Adaptec card, basically you should see a Adaptec Scsi bios screen just after the usual boot up screen when first powering on your system, on this screen on the far right you should see "160" if not it could be 80 or 40, if its 160 then your OK (press pause if you like). You can access the Scsi bios by pressing Ctrl A.

    As far as I know about the transfer rates, what they mean is that up to 160mb/s is achievable between devices through the LVD bus on the Adaptec card and not the SE bus or through the PCI to CPU buses which bottlenecks anyway.

    Burst speeds, seek times, disk-to-disk transfer rates on the same Scsi bus, latest technology and along with some extra features and reliability are the main advantages of Scsi.
    Do you have any other non-LVD devices on the LVD bus?
    Or do you have your LVD device on the "B" or second "SE" bus?
    The cheetah is on the end of the cable?
    The cable does have termination on the end? (Silly question)

    Also check the on disk jumpers, these can be confusing to set up and may have come set-up differently for what you want, make sure there is no jumper on "force se mode" or something to that wording.
    I could be wrong on some of the above so you can check out these sites>

    <A HREF="http://www.scsifaq.org/" target="_new">scsifaq.org</A>
    <A HREF="http://www.storagereview.com/welcome.pl/http://www.storagereview.com/guide2000/ref/hdd/if/index.html" target="_new">storagereview.com</A>

    Good luck...

    <font color=orange>Beam</font color=orange><font color=red> me</font color=red><font color=green> up</font color=green><font color=blue> Scotty</font color=blue> :wink:
  2. Thank you for your detailed reply. I think that I found one reason for my lower transfer rates:
    I have a non-lvd 80-68 pin adapter. The disk came with this adapter and of course it is the cheaper non-lvd version, so my drive is running in SE mode although it shows 160 next to it at the SCSI Bios screen.
    You mentioned a 64bit/66mhz PCI card slot motherboard.
    Could you recommend one manufacturer. I have not seen such boards before?
  3. Correct me if Iam wrong but 80 pin is for server situations on LVD, 68 pin is the same thing but for mid range/desktop situations but basically same thing different cable?
    Geesh this SCSI education goes on and on and on and....whatever.lol.

    So the Cheetah has 68pin or 80pin?

    Ok about these MB's, sure ya wanna know,heh, Of course ya do, wouldnt be in here otherwise huh.

    These boards are dual pocessor boards, I havn't seen any single ones as yet but they will be coming in the future.


    <A HREF="http://www.asus.com.tw/mb/socketa/a7m266-d/overview.htm" target="_new">ASUS-A7M266-D</A>

    <A HREF="http://www.tyan.com/products/html/systemboards.html" target="_new">Tyan boards</A>

    I think other board makers are onto it now so have a look around and watch the forum here and at <A HREF="http://www.storagereview.com" target="_new">http://www.storagereview.com</A>

    <font color=orange>Beam</font color=orange><font color=red> me</font color=red><font color=green> up</font color=green><font color=blue> Scotty</font color=blue> :wink:
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