Quadra 840av doesn't see any SCSI devices...please help!

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Last seen: 3 years 11 months ago
Joined: Jan 27 2011 - 12:51
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Quadra 840av doesn't see any SCSI devices...please help!

Hi all,

I'm trying to restore a Quadra 840av and am having SCSI issues. My fear is that the SCSI controller on the motherboard is fried and this computer cannot recognize any SCSI devices hooked to it internally or externally.

Here's the situation:

On power up, it chimes but the screen remains dark for almost 30 seconds (is that length normal?) and then it shows a grey screen with the cursor and the flashing "?" floppy icon. The cursor can be moved around with the mouse on that screen. So I am concluding that the Quadra has passed its initial diagnostics and now cannot find a System. Is that a reasonable conclusion?

The computer came with 2x internal HDs: a Seagate ST1100N 1GB and a Quantum Lightning ProDrive 730 MB. I have confirmed that both work when hooked up to a PowerMac G3. But when hooked up either internally or externally to the Quadra they spin up but are not recognized.

I am able to boot with an "Install Disk 1" floppy that I made from the "Install Me First" System 7.1 Installer CD that came with the Quadra. The computer gives me a happy Mac, and then the installer software starts and I can navigate the first screens and click onscreen buttons, etc. However, since the Quadra fails to recognize a hard drive, I cannot proceed with installation and can only choose Cancel followed by Restart or Shutdown.

So the good: The Quadra can boot from floppy and the installer software seems to run fine suggesting the CPU, input/output and RAM are OK.
The bad: no combination of internal or external hard drives are recognized by the Quadra, and it seems like the internal CD-ROM is also ignored (when I try to boot from a System 7.6 Installer CD the Quadra still gives me a flashing "?" disk symbol).

I know SCSI is voodoo, so I've tried different combinations of SCSI ID numbers, termination on/off, termination power on/off on the two HDs, a different SCSI cable, hooking up internally vs externally and the computer still fails to see these HDs.

Is there something I just don't understand about the 840av SCSI? I've read the 660/840av models are particularly touchy when it comes to SCSI setup...?

Any advice would be GREATLY appreciated!


Last seen: 4 years 5 months ago
Joined: Aug 21 2012 - 08:25
Posts: 4
Re: Quadra 840av doesn't see any SCSI devices...please help!

Dear Howie,

SCSI isnt rocketscience, its just slightly more complicated than IDE.
Basics are:

You need a cable to connect devices to the controller.
Where IDE has 8bit (xt drive), 40pin, 44pin and sata cables, SCSI has 50pin, 68pin, 80pin, fibrechannel, SAS and ISCSI cables.
(note: hardly any headache here...you only need to match cable to the connectors on the controller and harddisk).

SCSI-id is just an adres.
Where IDE has 2 adresses (master and slave) and a "cable select"-option (that works by swapping some adresslines in the cable
for device #2) SCSI has 7 adresses (#0 usually for contoller, rest manually distributed by you, the engineer)....no autoconfig at al.

Termination is what keeps communication between controller and harddisk clear.
Where IDE has no termination, in a SCSI-chain first (i.e. controller) and last device are decorated with terminating resistors.
Slight nag here is that terminators (&controllers&devices) come in 2 flavors, LowVoltage- and HighVoltage-Differential.
Just find out what the controller needs and go with that.

What's on the line?
Where IDE has harddisk, solidstate, cd/dvd, zip and bernoulli to choose from, SCSI sports harddisk, solidstate, cd/dvd, zip, tape and scanner.
Just use the wright one Smile

None of the above is a real problem....
What might be an issue is that Applesoftware (at least in the performa450 im fighting with) doesnt accept anything but its own brand of harddisk.
For system7 there is a patched "Apple HD SC Setup" to evercome that problem.

Just like you i'm battling SCSI...
I have a SCSi cdrom (ID 5, no term, middle of the chain) that works, allows me to boot from the 7.5.3 cdrom.
Controller is ID 0, harddisk is ID 2, terminated.
No harddisk is detected Sad
Issue in this machine is that it cannot read diskettes from my OSX 10.7 IMac, so getting the patched Apple HD SC Setup into that is somewhat of a challenge.

things you can check:
Google specs for controller and drives you have, observe LVD/HVD.
| HVD controller will destroy a LVD harddisk. |
| LVD controller will not see a HVD harddisk. |
Controller at one end of the cable, terminated harddisk at the other end.
Set controller ID to 0, disk ID to 3.
Fire up your install and start praying Smile

Grtz, PymerOne.

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