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Thread: Anyone know what the jumper "Local bus Bus-Mastering peripherals" does?

  1. #1

    Default Anyone know what the jumper "Local bus Bus-Mastering peripherals" does?

    So in my continuing quest of getting at least one of my Gateway 2000 machines up and running I was banging heads against a 486DX2-66V this weekend.

    The problem:

    One of the two VL-BUS Slots was occupied with a video card. I installed an Adaptec VL SCSI card in the other one but on boot I did not get the familiar Adaptec boot strap. I triple checked switch settings and tried multiple BIOS addresses and still no luck. I decided to swap the two VL-Cards and on boot I got a single nasty beep and a garbled screen display -> no post. After trying out multiple good cards I determined the issue was the second (closest to the PSU) VL-BUS.

    The solution:

    I did my best googlefu and luckily was able to find the motherboard (or an extremely close approximation) here. On that page it indicates that jumper W40 enables/disables "Local bus Bus-Mastering peripherals" As this was the only jumper related to the VL-BUS I disabled it (from its current enabled stats) and bam the second slot started working so that I could boot the video and SCSI cards.

    Unfortunately, I have no idea what the jumper does or why it would be enabled by default (and hence make one of the slots not work). Anyone know what the function of this jumper is? Does disabling it prevent bus mastering from occurring? TIA!
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. Copy II PC Enhanced Option Board (the one with the toggle switch on the back) 4. MicroSolutions MatchPoint AND/OR UniDOS card 5. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). If you have any of the above for sale please PM me. Thank you!

  2. #2

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    I have found that the biggest issue with VLB is the actual seating of the cards in their slots. It seems it's always been awfully difficult to get most VLB cards properly seated so that there are no booting issues like you have mentioned. Once I get a VLB card properly seated I immediately lock it down and hope that I never have to fool with it again.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  3. #3
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    Quote Originally Posted by Stone View Post
    I have found that the biggest issue with VLB is the actual seating of the cards in their slots. It seems it's always been awfully difficult to get most VLB cards properly seated so that there are no booting issues like you have mentioned. Once I get a VLB card properly seated I immediately lock it down and hope that I never have to fool with it again.
    Same here, VLB cards are always really tough to seat. Make sure the contacts on the card and in the slot are clean and just try reseating it until it works. Then just never touch it again unless it's absolutely necessary

  4. #4

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    Quote Originally Posted by Stone View Post
    I have found that the biggest issue with VLB is the actual seating of the cards in their slots. It seems it's always been awfully difficult to get most VLB cards properly seated so that there are no booting issues like you have mentioned. Once I get a VLB card properly seated I immediately lock it down and hope that I never have to fool with it again.
    Quote Originally Posted by RadRacer203 View Post
    Same here, VLB cards are always really tough to seat. Make sure the contacts on the card and in the slot are clean and just try reseating it until it works. Then just never touch it again unless it's absolutely necessary

    While I agree the cards are hard to seat I am pretty sure that was not the case. I even took off the bracket on the SCSI card initially to make sure that was not the issue.

    Unless of course both of you fine gents are suggesting that once I disabled the jumper it suddenly became easier to seat VLB cards so that now it works consistently with multiple removals and card swaps (I have been trying different video cards out)
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. Copy II PC Enhanced Option Board (the one with the toggle switch on the back) 4. MicroSolutions MatchPoint AND/OR UniDOS card 5. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). If you have any of the above for sale please PM me. Thank you!

  5. #5
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    VL bus mastering allows the card to control the bus instead of the CPU/DMA controller, for higher performance access to system memory. Unfortunately, it probably only works for one card as if it's enabled with two cards both try to be the bus master and only one works.

    It's probably a little lower performance than it'd be with only one VL-bus card installed, but the biggest benefit will be in 32 bit bus access, so you wouldn't see much performance difference.

  6. #6

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    Quote Originally Posted by Shadow Lord View Post
    Unless of course both of you fine gents are suggesting that once I disabled the jumper it suddenly became easier to seat VLB cards so that now it works consistently with multiple removals and card swaps (I have been trying different video cards out)
    No, but if you in fact reseated the VLB card(s) after having disabled the jumper you might have experienced the reseating effect at that point. I know that coincidences are iffy at best but there is still that possibility.

    And there's always the possibility that after several reseats the slot/card connections became better by having the friction of multiple insertions clean those contacts for better electrical connection.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  7. #7

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    Quote Originally Posted by HoJoPo View Post
    VL bus mastering allows the card to control the bus instead of the CPU/DMA controller, for higher performance access to system memory. Unfortunately, it probably only works for one card as if it's enabled with two cards both try to be the bus master and only one works.

    It's probably a little lower performance than it'd be with only one VL-bus card installed, but the biggest benefit will be in 32 bit bus access, so you wouldn't see much performance difference.
    Interesting, I always thought the VL-BUS could handle more then one bus master card but according to this FAQ it has poor bus arbitration. Which then begs the question why have more then one VL slot on a MB (specially considering that the system becomes unstable at 3 slots and sometimes even with two with the cheaper boards). I think the drop in performance will be pretty much negligible if all you lose is bus mastering given that SCSI should do transfers on the chain without the main CPU (i.e. from CD to HDD).
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. Copy II PC Enhanced Option Board (the one with the toggle switch on the back) 4. MicroSolutions MatchPoint AND/OR UniDOS card 5. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). If you have any of the above for sale please PM me. Thank you!

  8. #8

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    Quote Originally Posted by Stone View Post
    No, but if you in fact reseated the VLB card(s) after having disabled the jumper you might have experienced the reseating effect at that point. I know that coincidences are iffy at best but there is still that possibility.

    And there's always the possibility that after several reseats the slot/card connections became better by having the friction of multiple insertions clean those contacts for better electrical connection.
    Yeah, I am going to give that a nugatory good buddy specially since the problem reoccurs when I re-enable the jumper....
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. Copy II PC Enhanced Option Board (the one with the toggle switch on the back) 4. MicroSolutions MatchPoint AND/OR UniDOS card 5. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). If you have any of the above for sale please PM me. Thank you!

  9. #9

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    In case anyone else ever comes looking for this tidbit here is more info on the jumper.
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. Copy II PC Enhanced Option Board (the one with the toggle switch on the back) 4. MicroSolutions MatchPoint AND/OR UniDOS card 5. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). If you have any of the above for sale please PM me. Thank you!

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