PM 5500 External SCSI Woes

[ObeyDaleks]

Hi all,

I'm experiencing a weird issue. When I plug in a my BlueSCSI DB25 drive to the external SCSI connector, the machine hangs on boot. Happy chime, but no icon, just a mouse pointer. I have 2 logic boards actually, one from the PM5500, which is completely recapped and one from a 6500 which is not recapped. Both logic boards are exhibiting the same exact issue. The BlueSCSI drive works on literally every other Mac I have.

The PM5500 machine is fully recapped (both PSU and analog board). Everything else works perfectly with either of the two logic boards. The SCSI CD-ROM works, and it boots fine off a SATA SSD drive.

I tested all voltages on the SCSI connector, and they are all fine. The BlueSCSI drive lights up.

Not sure what else to try. I feel like I'm missing something obvious. Any ideas?

 

[croissantking]

You didn’t mention termination, does the bluescsi provide this?

 

[ObeyDaleks]

Thanks for the reply. Yes, the BlueSCSI DB25 has onboard termination. I also tried changing the SCSI IDs just in case (although I do know there should not be a conflict - the CD ROM is ID 3, and the IDE drive is irrelevant). Lastly, I tried other SD cards in the BlueSCSI. The oddest thing is, it's not just an issue of drive not being recognized - it actually seemingly prevents the machine from initializing its ROM (since I never get any icon on the screen during boot, just the mouse pointer).

Interestingly, when I connected an external SCSI CD ROM drive this morning, it worked fine. So it's not external SCSI in general as I previously thought, it is specifically that BlueSCSI DB25 device that's the problem. Or more precisely, it is the combination of this specific machine and this specific BlueSCSI drive (or possibly BlueSCSI DB25 in general) that's the issue. Apparently, other SCSI devices work fine on this machine, and the BlueSCSI drive works fine with every other Mac, including PowerMacs of the same era. Totally perplexing.

 

[croissantking]

So maybe either the host or the device may not be 100% standards compliant here.

 

[ObeyDaleks]

So maybe either the host or the device may not be 100% standards compliant here.

Yeah, that's a good theory. Or possibly the PM 5500/6500 board is more strict/finicky about standards compliance, and other machines are more "tolerant". That might explain why the Apple-branded external CD ROM still works fine, but the (aftermarket hack) BlueSCSI (v1.1) does not. I might get an external BlueSCSI v2 or other similar "higher quality" device, and see what happens. I do have some BlueSCSI v2 internal drives, so maybe just an adapter might do it. Thanks for your help!

 

[croissantking]

Which version of BlueSCSI do you have there? Guessing it is 1.1a or older?

Would recommend a ZuluSCSI RP2040 - I've had a great experience with mine.

 

[ObeyDaleks]

Which version of BlueSCSI do you have there? Guessing it is 1.1a or older?

Would recommend a ZuluSCSI RP2040 - I've had a great experience with mine.

I updated my post - yeah it's v1.1a. I'll def look into ZuluSCSI. Thanks again.

 

[ObeyDaleks]

Just an update. BlueSCSI 2.0 (DB25 version) did indeed work like a charm. So it must not have liked the 1.1a version for whatever reason. Thanks, @croissantking for the advice.

 

[croissantking]

Glad to hear! I think BlueSCSI 1.1a is a bit broken.