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Terminating a LVD/SE SCSI for Quadra

SirFoxx

SirFoxx

macrumors regular
Original poster
Jul 9, 2012
137
2
Galien, Michigan
I know I posted about this before, but I was not able to add onto the thread due to not being able to get a mac with scsi running.

I just got my beige G3 up ad running with OS9, and I've been trying to get an IBM 18gb 68pin (DNES-318350) drive partitioned for my quadra 950. Since this is a LVD/SE drive, there is not a built in terminator on the logic board of the drive, which means an external terminator is needed. I was wondering if the terminator that originally came with my quadra would work, or if I need one meant for a LVD/SE drive.

The reason I ask about the terminator is because I cannot get the G3 to recognize the drive, even though I have "S/E mode" jumpered, and using a 3rd party formatting tool (mt. everything, and a scsi probing tool). I know there is mention of powering the terminator, which leads me to believe the one that originally came with the Quadra will not work. Attached are pics of the 50-68 pin adapter, quadra terminator, and the jumper chart for the drive.



 
MacTech68

MacTech68

macrumors 68020
Mar 16, 2008
2,393
209
Australia, Perth
Seems there are two models with a 68Pin connector.

A pic of the full logic board of the drive will make it easy to tell which it is. On the Multi (LVD/SE) model U5 is missing but is present on the SE only model.

I'm assuming hereafter that you have the LVD/SE Multimode version.

Settings I used to use on these drives is:

Disable Unit Attention - jumper on
Force SE mode - jumper on
Enable Auto Spin - jumper on

From your first pic, you appear to have jumper position 5 jumpered (Enable Auto Spin) so the drive is still trying to work as LVD, and this won't work.

One problem I can see is that the pitch of the jumper you have looks to be too wide. There are generally two different pitched jumpers for later SCSI hard drives. 2.54mm pitch is the older type (and may fit the option jumpers next to the power connector but do nothing for this drive model) and the type you need for the 10 pin jumper options is 2.0mm.

You will certainly need a terminator fitted to the physical end of the SCSI Cable. The old "passive" terminator should work, but isn't as precise as an "active" terminator (Active terminators have their own voltage regulator for more accurate voltage). Active is better, but probably NOT necessary at these low SCSI BUS speeds.

Note that the Mac's motherboard has one terminator, and you need one at the OTHER physical end of the SCSI cable. That's the theory. "SCSI Voodoo" sometimes proves otherwise (ie, removing the terminator at the loose end of the SCSI cable may make everything work and adding it may stop it from working). :eek:
 
SirFoxx

SirFoxx

macrumors regular
Original poster
Jul 9, 2012
137
2
Galien, Michigan
Good news and bad news--Bad news is that with the three jumpers and the terminator, it didn't work, even when I tried it without the terminator. Good new is that I found the terminator that was hooked up in conjunction with the drive. Looks like I will be needing another adapter. As far as I know, this is the LVD/SE 68 pin drive. From the manual, there was a 50 pin with the built in terminator, then a 68/80 pin multimode without the terminator.



 
Last edited:
MacTech68

MacTech68

macrumors 68020
Mar 16, 2008
2,393
209
Australia, Perth
Yes, from your last pic, I can see that the terminator IC is not fitted so you definitely (theoretically) need a terminator.

I'm a little surprised that it didn't work with a passive terminator.

As you suggest, the only way to proceed now is to get another adapter to utilize the 68pin terminator.

--------------------------------------------------
Academic- (informational purpose only) :)

The manual for these drives is a little difficult to read. The version I have does seem to indicate that there were 4 models of drives.

1. 50 Pin Single Ended
2. 68 Pin Single Ended Only with built in terminator
3. 68 Pin Single Ended/LVD "multimode" with no terminator
4. 80 Pin LVD only

If you look at it, why else would the 68Pin circuit board have a position for a terminator IC.
 
SirFoxx

SirFoxx

macrumors regular
Original poster
Jul 9, 2012
137
2
Galien, Michigan
I probably should have updated this post awhile ago. Right before I left for college I received my 50-68-80 pin SCSI adapter, hooked it up along with the active terminator, and got everything working with the G3. I made ~900mb partition as HFS and left the other ~17gb as HFS+. Bit of a waste, but I will look into if I can utilize that with the quadra later when I'm back home. As for getting it to work with the quadra, not sure yet as I had to leave for college the next day, and left it at that. Theoretically it should since there is an HFS partition. I will post a pic here with my results when I can work on it next.
 
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