IIGS Rom 3 with Rev C SCSI Card - Crashes to monitor on boot

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sev
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IIGS Rom 3 with Rev C SCSI Card - Crashes to monitor on boot

Hello,

 

I have a rom 3 IIGS that came with a rev 3 scsi card. I find the card to be extremely unstable. Without the card, my IIGS runs just fine, but with the card, (which i use for booting GS/OS off a scsi zip card) the card is extremel unstable. About 80 to 85% of the time that I power up the machine with the rev c scsi card in there, it boots and crashes to the monitor. It'll do this whether or not i'm using the micronics scsi drive it came with or my zip drive. It'll even do this when nothing is plugged into the scsi. Once in a while, it'll boot right into GS/OS, but it's pretty rare. I've even checked the sole electrolytic capacitor on the card and it checks out fine.

 

I thought the problem was the SCSI termination power so I did the diode mod, but nothing changed. The card sits in slot 7 and the config is set to 'your card' for slot 7 as well. I have replaced my power supply with what is known to be good and verified the voltages coming out of them when the machine is powered on. 

 

This has been driving me crazy forever, I could use some help!

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Does it only do this when

Does it only do this when powering up? That is, does a OA-CTRL-RESET work correctly every time after the computer has been turned on?

 

Might need a delay after power up to work correctly.

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jeffmazur wrote:

Does it only do this when powering up? That is, does a OA-CTRL-RESET work correctly every time after the computer has been turned on?

 

Might need a delay after power up to work correctly.

 

One of my IIgs's will only boot when a SCSI card is on slot 1 (maybe 2). It won't work past that... I was never able to figure it out. I assumed it needed recap or some other component was "weak".

 

sev
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jeffmazur wrote:

Does it only do this when powering up? That is, does a OA-CTRL-RESET work correctly every time after the computer has been turned on?

 

Might need a delay after power up to work correctly.

 

nope. It wont work even on a soft reset.

 

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That was going to be my next

That was going to be my next question: does the board work in a lower slot? If so, it might be a bus timing/loading issue.  Or again, it might need the extra time after a reset before the slot scanning routine gets to the lower slot number.

 

Does PR# slot work reliably?

sev
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That's a good question, I've

That's a good question, I've never tried it lower than slot 5. I also havent tried doing the pr# command. Let me try it and see what happens

 

sev
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So i had a chance to try

So i had a chance to try using the pr command. Which either causes it to hang or crash back to monitor. I also tried slot 1 and set it to 'your card'. No difference. Still crashes to monitor.

 

So super frustrating 

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That's a bummer. It sounds

That's a bummer. It sounds like the card is defective...

 

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I attempted the termination

I attempted the termination power mod and either it did not work or I did something wrong. I was unwilling to be dependent on using drive chaining or the diagnostic gadget I have so I took a closer look at the specs and I found a jumper next to a letter on the bottom of the hard drive. When I changed it, Voila! It works now. But what happens when I have another SCSI drive? Well, if my SCSI card does not provide the termination power then I will be unable to hook up another SCSI hard drive in the way I want to. I looked at that gif picture many times and I also looked at a few schematics which were wrong and I still have no termination power.

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Generally you would make sure

Generally you would make sure your device that supports termination power is the last one on the external chain.

 

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You could get a terminator

You could get a terminator that does term power.

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