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Thread: Options For Empty A2091 SCSI Hard Card

  1. #1
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    Default Options For Empty A2091 SCSI Hard Card

    Along with the purchase of an Amiga 2500 came an A2091 hard card. ROMs are Version 7 but otherwise the board is bare: A stub for power and data and a place for a SCSI drive to be attached to the card; 16 empty sockets for RAM.

    Apart from what I could learn in the Amiga Hardware Database I know nothing about this card so may I ask:

    -Is it advisable to put a SCSI disk on the card or is it better to run a 50-pin cable to the chassis below the FDs?

    -Is it advisable to populate the empty RAM sockets?

    -Has anyone modified the board to install a 2x20 header and successfully run an IDE drive from the card? If so, how much is involved?

    Thanks for your replies

    -CH-

    Pic:

    A2091 Hard Card.jpg

  2. #2

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    Locating the hard drive only depends on cooling and air flow in your particular installation. Also, mounting on the card opens up that other bay for another drive. With careful consideration of the SCSI bus you design, you can have external and internal drives, mounted wherever it's convenient.

    Yes, populate those RAM sockets as much as you can. You only get 8Mb of address space on the bus, so you'll have to deduct whatever addressing is tied up on other boards. There's a modern Ethernet solution (sorry I don't recall which; it has USB on board) that I found ties up a significant amount of space, and so does not play well with the 209x. You want as much RAM there as you can for two reasons: having any RAM there switches the SCSI controller from PIO to DMA, and these days maxing out your Zorro II RAM is not prohibitive, and just makes the whole system better.

    DMA is incredibly faster than PIO in these systems.

    I have not installed the IDE components on that card, but I did do it on a third party card that used the same chip set, and it worked. Someone here was discussing doing this to a 209x recently, you might be able to find the thread.

    I think you have the latest ROMs, which is highly advisable.
    Last edited by KC9UDX; December 5th, 2017 at 01:37 PM.

  3. #3
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    In my A2091, the scsi drive is mounted on the board. I have no other board that will cause interferance space-wise, besides, I don't have any longer scsi cable on hand.

  4. #4

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    I found that I could buy a large spool of cable and a number of connectors for less money than a good pre-made cable. The best part is, then the connectors always end up where you need them.

    If you don't have a card in the accelerator slot, a drive mounted on the board in the rightmost Zorro slot in probably just as good for cooling as one mounted in a drive bay. It won't have as much conductive cooling, but it's probably not enough to matter.

  5. #5
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    Quote Originally Posted by KC9UDX View Post
    I found that I could buy a large spool of cable and a number of connectors for less money than a good pre-made cable. The best part is, then the connectors always end up where you need them.

    If you don't have a card in the accelerator slot, a drive mounted on the board in the rightmost Zorro slot in probably just as good for cooling as one mounted in a drive bay. It won't have as much conductive cooling, but it's probably not enough to matter.
    Thanks to all for their replies. In light of the DMA issue, which I had not previously considered, I will pursue populating the card's RAM. Because I would like to leave space for a coprocessor and because of the potential for thermal conduction of the drive bay I think I will opt for using a longer cable. It happens I have one.

    I also have another SCSI card, one which came with the A2000. Pictured below, I am not sure who made this one or what its model number is. Looks like Commodore. Any ideas?

    Making your own ribbon cable is getting more expensive - the connectors are still cheap but the ribbon is getting pricey - but cheaper and faster than finding one pre-made. The A2000's FD cable came apart in my hands recently and I was able to repair it by replacing the connector. The 4-6 twist makes this cable especially hard to find.

    Thanks again for your help.

    -CH-

    OtherSCSI.jpg

  6. #6

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    If you have the space, external drives are the way to go. No extra heat inside the case. You can reconfigure your bus very easily without opening the case. If a drive should give up the ghost, replacement is easy.

    I've seen at least a dozen different Amiga SCSI cards but I don't recognise that one. There yoostsaby several sites with pictures of various Amiga expansion cards; not sure if any are still around.

  7. #7
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    After a little further consideration I realized that this card has an ST506 interface at the top of the card. I searched for "Commodore combination MFM and SCSI controller card" and the Google result led me to
    http://www.bigbookofamigahardware.co...t.aspx?id=1160, which identifies this as an A2090 or A2090A. Mine resembles the Rev. 5 board, I think.

    May or may not support autobooting; can't read the writing on the ROMs. I'll know more when the A2000 is fully assembled. (It's a long story...)

    -CH-

  8. #8

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    Pretty sure I have one of those. Old age probably prevents me from recognising it!

  9. #9
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    That card pictured is a A2090A, because it has ROMS for autobooting. It supports ST506 drives and SCSI. I have two of these and they are rather difficult to set up. I mounted a 40 pin header on a A2091 card, but be advised that it is for the old 8 bit, XT-IDE, or XTA hard drives. Those types of drives are never more than 40 meg. and are difficult to source. I don't believe it will accept a standard IDE hard drive.

    The A2090 card is a development of the A590 hard drive add on for the A500. They were equipped with an XTA hard drive. When the A2091 was developed, Commodore didn't change the design of the electronics, they just left the 40 pin header off since by that time the XTA drives were fading.
    Last edited by fatwizard; December 6th, 2017 at 10:40 AM.

  10. #10
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    Quote Originally Posted by fatwizard View Post
    That card pictured is a A2090A, because it has ROMS for autobooting. It supports ST506 drives and SCSI. I have two of these and they are rather difficult to set up.
    My luck holds...

    Quote Originally Posted by fatwizard View Post
    I mounted a 40 pin header on a A2091 card, but be advised that it is for the old 8 bit, XT-IDE, or XTA hard drives. Those types of drives are never more than 40 meg. and are difficult to source. I don't believe it will accept a standard IDE hard drive..
    I'm abandoning that line of inquiry as I will never want to use the Amiga as an IBM PC clone.

    Thanks again for your replies. I may need to ask again for help when it comes time to reassemble the A2000: Although it came with a functioning SCSI drive I don't know if controller and drive tandem can autoboot.

    -CH-

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