Re: Suggestions for "the fastest" Q22/SCSI-interface? - VMS

This is a discussion on Re: Suggestions for "the fastest" Q22/SCSI-interface? - VMS ; Tim Shoppa wrote: > I did (and published) some benchmarks of SCSI MSCP-emulating > controllers probably a decade ago. And indeed the CMD CQD 440 was the > winner. But they all beat the pants off a RQDX3! > > ...

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Thread: Re: Suggestions for "the fastest" Q22/SCSI-interface?

  1. Re: Suggestions for "the fastest" Q22/SCSI-interface?

    Tim Shoppa wrote:
    > I did (and published) some benchmarks of SCSI MSCP-emulating
    > controllers probably a decade ago. And indeed the CMD CQD 440 was the
    > winner. But they all beat the pants off a RQDX3!
    >
    > Here are the peak data rates measured for read and write 64
    > blocks-at-a-time:
    >
    >
    > Read Write
    > ---------- ----------
    > Andromeda SCDC 2.298 MB/s 1.131 MB/s
    > CMD CQD440 2.397 MB/s 1.525 MB/s
    > CMD CQD220 1.418 MB/s 0.882 MB/s
    > CMD CQD220A 2.088 MB/s 1.409 MB/s
    > DEC RQZX1 1.379 MB/s 1.097 MB/s
    > Viking QDT 0.846 MB/s 0.704 MB/s
    > DEC RQDX3 0.164 MB/s 0.161 MB/s
    >
    > The benchmarks were done under RT11FB 5.7 doing 1, 2, 4, 8, 16,
    > 32, and 64 block-at-a-time READW's and WRITW's to 16384-block
    > data files. A KDJ11B (PDP-11/73) CPU with 2 Megabytes of Clearpoint
    > non-PMI memory was used for the bencharmks. With the SCSI
    > controllers a Barracuda 7200 RPM ST15230N drive was used; with
    > the RQDX3 a RD52 drive was used.
    >
    >
    > Tim.
    >
    >

    Interesting. To add an additional data point, I have been playing with a
    programmed I/O disk interface and get about 0.250MB/s. Which beats the
    RQDX3...

    Tim: If you have your benchmark program available and it would run on
    V5.03, I would be interested.

    I was just looking at the Qbus protocol diagrams and it looks like the
    absolute minimum cycle time is 350ns. The maximum transfer rate is then
    5.714MB/s. This is assuming continuous block mode DMA transfers. The
    protocol limits it to 16 words without a bus arbitration. The true
    absolute maximum is less. There is no allowance for memory speed either.

    Am I correct about this?

    -chuck




  2. Re: Suggestions for "the fastest" Q22/SCSI-interface?

    On 19 Apr, 01:52, Charles H Dickman wrote:
    > Tim Shoppa wrote:
    > > I did (and published) some benchmarks of SCSI MSCP-emulating
    > > controllers probably a decade ago. And indeed the CMD CQD 440 was the
    > > winner. But they all beat the pants off a RQDX3!

    >
    > > Here are the peak data rates measured for read and write 64
    > > blocks-at-a-time:

    >
    > > Read Write
    > > ---------- ----------
    > > Andromeda SCDC 2.298 MB/s 1.131 MB/s
    > > CMDCQD440 2.397 MB/s 1.525 MB/s
    > > CMD CQD220 1.418 MB/s 0.882 MB/s
    > > CMD CQD220A 2.088 MB/s 1.409 MB/s
    > > DEC RQZX1 1.379 MB/s 1.097 MB/s
    > > Viking QDT 0.846 MB/s 0.704 MB/s
    > > DEC RQDX3 0.164 MB/s 0.161 MB/s

    >
    > > The benchmarks were done under RT11FB 5.7 doing 1, 2, 4, 8, 16,
    > > 32, and 64 block-at-a-time READW's and WRITW's to 16384-block
    > > data files. A KDJ11B (PDP-11/73) CPU with 2 Megabytes of Clearpoint
    > > non-PMI memory was used for the bencharmks. With the SCSI
    > > controllers a Barracuda 7200 RPM ST15230N drive was used; with
    > > the RQDX3 a RD52 drive was used.

    >
    > > Tim.

    >
    > Interesting. To add an additional data point, I have been playing with a
    > programmed I/O disk interface and get about 0.250MB/s. Which beats the
    > RQDX3...
    >
    > Tim: If you have your benchmark program available and it would run on
    > V5.03, I would be interested.
    >
    > I was just looking at the Qbus protocol diagrams and it looks like the
    > absolute minimum cycle time is 350ns. The maximum transfer rate is then
    > 5.714MB/s. This is assuming continuous block mode DMA transfers. The
    > protocol limits it to 16 words without a bus arbitration. The true
    > absolute maximum is less. There is no allowance for memory speed either.
    >
    > Am I correct about this?
    >
    > -chuck


    Interesting, indeed! I'm about placing an order, I found one at a
    price that's god enough, and this benchmark sent "god wibrations" on
    the type!

    And regarding CMD-types: Yes; I agree to your old memories, and want
    to add...
    Someone wrote: The CQD 420 is a 440 without the differential side
    populated
    440 is surely a quad-wide card. I THINK i remember some writing of a
    420 being dual, no guarantees given!

    /TM means TMSCP & MSCP (ie Tape & Disc combined on the same SCSI-
    bus)
    /TMP means TM + "PassThru" (I GUESS this means: no internal
    terminator)
    /TMS means TM + "Hardware Shadowing"
    TMP and TMS taken from a 440/443 manual I found on-line.

    I have seen some different models, but NEVER a 420 or 420 /T or /M.
    That was the older days...

    I have also found:
    CQD 200...
    CQD 220/TM ?
    CQD 220A/TM SCSI-2 5 MByte/sec peak
    CQD 420/TM Fast SCSI-2 up to 10 MByte/s peak
    Add 3 to any model number to get S-handles... I dont known how "old"
    models this is valid for, though.

    So, now I will have to wait for shimpment and se if a manual is
    included...

    I'm sorry, I didn't write data of those old controllers when they
    passed my screen last night in search of the more modern types...


    Best regards, and thanks for help, /Göran

  3. Re: Suggestions for "the fastest" Q22/SCSI-interface?

    On Apr 22, 7:01*pm, sm6nnc wrote:
    > On 19 Apr, 01:52, Charles H Dickman wrote:
    >
    >
    >
    >
    >
    > > TimShoppawrote:
    > > > I did (and published) some benchmarks of SCSI MSCP-emulating
    > > > controllers probably a decade ago. And indeed the CMD CQD 440 was the
    > > > winner. But they all beat the pants off a RQDX3!

    >
    > > > Here are the peak data rates measured for read and write 64
    > > > blocks-at-a-time:

    >
    > > > * * * * * * * * * Read * * * * * Write
    > > > * * * * * * * * * ---------- * * ----------
    > > > Andromeda SCDC * *2.298 MB/s * * 1.131 MB/s
    > > > CMDCQD440 * * * 2.397 MB/s * * 1.525 MB/s
    > > > CMD CQD220 * * * *1.418 MB/s * * 0.882 MB/s
    > > > CMD CQD220A * * * 2.088 MB/s * * 1.409 MB/s
    > > > DEC RQZX1 * * * * 1.379 MB/s * * 1.097 MB/s
    > > > Viking QDT * * * *0.846 MB/s * * 0.704 MB/s
    > > > DEC RQDX3 * * * * 0.164 MB/s * * 0.161 MB/s

    >
    > > > The benchmarks were done under RT11FB 5.7 doing 1, 2, 4, 8, 16,
    > > > 32, and 64 block-at-a-time READW's and WRITW's to 16384-block
    > > > data files. *A KDJ11B (PDP-11/73) CPU with 2 Megabytes of Clearpoint
    > > > non-PMI memory was used for the bencharmks. *With the SCSI
    > > > controllers a Barracuda 7200 RPM ST15230N drive was used; with
    > > > the RQDX3 a RD52 drive was used.

    >
    > > > Tim.

    >
    > > Interesting. To add an additional data point, I have been playing with a
    > > programmed I/O disk interface and get about 0.250MB/s. Which beats the
    > > RQDX3...

    >
    > > Tim: If you have your benchmark program available and it would run on
    > > V5.03, I would be interested.

    >
    > > I was just looking at the Qbus protocol diagrams and it looks like the
    > > absolute minimum cycle time is 350ns. The maximum transfer rate is then
    > > 5.714MB/s. This is assuming continuous block mode DMA transfers. The
    > > protocol limits it to 16 words without a bus arbitration. The true
    > > absolute maximum is less. There is no allowance for memory speed either.

    >
    > > Am I correct about this?

    >
    > > -chuck

    >
    > Interesting, indeed! I'm about placing an order, I found one at a
    > price that's god enough, and this benchmark sent "god wibrations" on
    > the type!
    >
    > And regarding CMD-types: Yes; I agree to your old memories, and want
    > to add...Someone wrote: The CQD 420 is a 440 without the differential side
    >
    > populated
    > 440 is surely a quad-wide card. I THINK i remember some writing of a
    > 420 being dual, no guarantees given!
    >
    > /TM means TMSCP & MSCP * (ie Tape & Disc combined on the same SCSI-
    > bus)
    > /TMP means TM + "PassThru" * (I GUESS this means: no internal
    > terminator)
    > /TMS means TM + "Hardware Shadowing"
    > TMP and TMS taken from a 440/443 manual I found on-line.


    Ahah, now I remember: The "PassThru" was a way of sending SCSI
    commands through to raw devices. I asked around at the time it was new
    (late 80's?) and was told it was for doing CD and magtape magazine-
    changing but required some custom drivers to get it done.

    All of them (maybe exception of RQZX1) had selectable termination that
    could be put in and out. At least one brand (maybe CMD, maybe
    Andromeda?) could have terminators turned on and off by software
    configuration.

    Hardware shadowing makes sense where you need shadowing... I know that
    some RSX versions supported hardware shadowing for MSCP. Seems like
    way overkill for a hobby application.

    As to the source to my benchmark program, it was literally just
    some .READW's and .WRITW's, probably done through Fortran for off-the-
    cuffness. Since it's RT-11, by definition the blocks are
    contiguous :-).

    You're probably right about the 440 vs 420. I think both were quad-
    height but I'm really stretching my memory again.

    Tim.

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