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Connect two external drives to Color Classic?

djorud

Active member
Is it possible to simultaneously connect two external hard drives to a Color Classic? I have two external drives with 50 pin Centronic ports. One is an Apple drive, while the other is not. I have attempted to do so using a double male 50 pin cable between the two drives, then using a 50 pin to 25 pin cable to connect to the Color Classic. Only one drive, the Apple 1GB, shows up on the CC desktop. If I shut the CC down, then shut the Apple drive off before restarting the CC, then the other drive will show up on the CC desktop. I have used a terminator on one drive as well as trying without. No change. As the CC only has the one 25 pin port, I am concluding that’s the limit - only one external drive at a time. Is this a correct assumption, or is there a workaround to connecting two external drives simultaneously? Thanks much for any wisdom you can offer.
 

foetoid

Well-known member
Do the external drives have the same SCSI ID? That would be my first guess as to why you're seeing only one drive show up.
 

foetoid

Well-known member
So, the SCSI bus should support 8 devices (0-7). I know there can be some reservations for some of those bus IDs for specific purposes. For instance, ID 7 is for the machine itself, and I think SCSI ID 3 is sometimes reserved for a CD-ROM drive. (I'm going off of 20 year old recollections, so there could be some variation here.)

From recollection, I remember that the Apple HDs didn't typically have jumpers to adjust SCSI IDs, but non-Apple devices typically did.

I suppose it's possible that the Color Classic could be different I've never had one...

Not sure that this is at all helpful. Sorry I can't be of more help. I wish you success in your journey.
 

bibilit

Well-known member
Yes, no problem connecting several devices to the external SCSI port.

Devices should been daisy chained together, the last on the chain should be terminated
 

Phipli

Well-known member
Adding to the existing answers, the internal hard disk, and each external all need their own IDs, which can not be 7. Plus, if using one of those little ID numeric setting things on an external drive, double check it is actually connected to the drive inside the enclosure because I have enclosures where it isn't because it didn't fit a replacement disk.

Make sure the chain is terminated and only once externally.

Are you using an SD card SCSI adapter at all?
 
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ArmorAlley

Well-known member
Is it possible to simultaneously connect two external hard drives to a Color Classic?
Yes it is and I suspect that you have either a SCSI-ID conflict (multiple devices with the same ID) or improper termination.
Of course, faulty cabling or enclosures could also be to blame.
Have you also taken the internal HD into consideration?

Would you take a screengrab (say with Snapz) of the control panel SCSIProbe 4.0 and load it up to this thread please?
If you don£t have it, SCSIProbe can be found here: https://macintoshgarden.org/apps/scsiprobe
Snapz can be found here: https://macintoshgarden.org/apps/snapz-pro-1
 

MrFahrenheit

Well-known member
I have four external drives connected here without issue.

Like collectively has been said, each one requires its own SCSI ID, and make sure it’s actually set to the ID you’re selecting. Try using only one at a time and installing SCSI Probe on your boot drive and verifying the ID number of each drive you’ve set.

Terminator is required, not optional! It goes at the end of the chain.

Ultimately, it should look like this:

Color Classic -< 25 pin -> 50 pin -> first drive <- 50 pin -> 50 pin -> second drive <- 50 pin terminator
 

djorud

Active member
Thanks very much for weighing in on my question. Clear to me I have some more work to do. I don’t have SCSI Probe or Snapz, so will download them and find a way to put onto a floppy disk so I can see whats going on over on the CC. Might be later in the week, as I have been assigned to some holiday tasks the next couple of days that will eat up my time. Will post more when I’ve done my homework!
 

Phipli

Well-known member
Will post more when I’ve done my homework!
Remember, the answer is always, one, zero, infinity or "the character cannot be read in these simple terms as their behaviour is multi faceted".

And I personally think George was wrong to kill Lenny.
 

djorud

Active member
Not sure if this makes a difference or not….but, when the second external hard drive is the only one being used, TWO separate icons appear on the desktop, “OS6” and “OS7”. In contrast, the other external hard drive only appears as one icon, “1GB”.

The second external HD has the manually switchable ID on the back. I have switched it to two different settings, , “2” and “3”. It was originally a “1” before attempting to add the second external HD.

Again, not sure if these added tidbits provide any further insight into the problem or not.
 

djorud

Active member
Next step has been done, downloading SCSI Probe onto floppy disk. But, can’t open it due to “no default program” being selected. What program is needed? I downloaded the most recent version of SCSI Probe that was available, which was second to last version.
 

Phipli

Well-known member
Not sure if this makes a difference or not….but, when the second external hard drive is the only one being used, TWO separate icons appear on the desktop, “OS6” and “OS7”. In contrast, the other external hard drive only appears as one icon, “1GB”.
This means the one has two partitions and the other only has one. It doesn't impact what you're doing.
The second external HD has the manually switchable ID on the back. I have switched it to two different settings, , “2” and “3”. It was originally a “1” before attempting to add the second external HD.
You need to check to make sure that the cable from the switch is actually plugged into the disk inside, but also you haven't mentioned what the other disk is set to? Its unusual for there not to be a selector on an external to be honest. You also need to confirm the internal disk's id.
Again, not sure if these added tidbits provide any further insight into the problem or not.
Helps some, but not a full picture yet :)

How do you have termination set up?
 

Phipli

Well-known member
Next step has been done, downloading SCSI Probe onto floppy disk. But, can’t open it due to “no default program” being selected. What program is needed? I downloaded the most recent version of SCSI Probe that was available, which was second to last version.
What is the file extension if there is one?

The answer is most likely "Stuffit Expander" which might already be on your machine. I usually install version 4 and version 5, because each doesn't like some files the other is happy with.
 

djorud

Active member
Okay, will do further checking. My old classic macs are located in another building, so not conveniently accessible when replying here. But, the first external HD is one of vertically oriented Apple models with the push button on/off switch on top front. Will need to look at it again for an ID switch on the back.

As for termination. I do have the second HD terminated at one of the two 50 pin connections. I have switched the terminator to the other, but makes no difference. It still does not appear on desktop unless I switch the first HD off.

At this point, haven’t taken the second HD out of the case to make sure the ID switch is physically connected. I purchased he HD drive new maybe 15 years ago, but only used it for a few months before storing it away. Never had it apart.

If I don’t have Stuffit Expander on the CC, will take care of that as well.

Looks like I’m being beckoned away now to begin the holiday tasks at hand, so might be a couple of days before I return here….unless I can manage to break free again!
 

Phipli

Well-known member
Okay, will do further checking. My old classic macs are located in another building, so not conveniently accessible when replying here. But, the first external HD is one of vertically oriented Apple models with the push button on/off switch on top front. Will need to look at it again for an ID switch on the back.
If it is the enclosure I think you mean it is here :
m2115__0012.jpg
(from here http://appletothecore.me/files/m2115_external_drive.php )
As for termination. I do have the second HD terminated at one of the two 50 pin connections. I have switched the terminator to the other, but makes no difference. It still does not appear on desktop unless I switch the first HD off.
It isn't completely clear what you mean, when you have time it is worth describing how everything is wired and terminated when you have more time. It needs to be right, and probably is, but we can't dismiss it without know what is where, cables, order and termination.
At this point, haven’t taken the second HD out of the case to make sure the ID switch is physically connected. I purchased he HD drive new maybe 15 years ago, but only used it for a few months before storing it away. Never had it apart.
If it is yours since new it will be fine.
If I don’t have Stuffit Expander on the CC, will take care of that as well.
Looks like I’m being beckoned away now to begin the holiday tasks at hand, so might be a couple of days before I return here….unless I can manage to break free again!
Have fun :)
 

Phipli

Well-known member
Actually, just set the drive with the ID on the back to ID 6 and try it. It will take less time and /most likely/ fix all your problems so you can get on with things. If that doesn't work then you have to investigate as described above.
 

MrFahrenheit

Well-known member
Like many have said, there are likely only a few reasons this is causing you trouble.

1. Termination
2. SCSI ID conflict
3. Hot swapping drive cables and devices.

Termination is easy. If only one device exists in a machine, that device needs to be terminated. If it’s internal, then that internal drive needs to be terminated. If more than one device exists, the first and last device need to be terminated and only the first and last device. The first being the one inside the machine (if present) and the last being at the end of the device chain. If there is no internal device, some Mac’s have built in termination to act as the internal device, and self-terminatd, and some require a termination block be applied INSIDE at the scsi connector, to stand in for a missing internally terminated drive.

You say you have an internal drive. What kind of drive is it, and is it the original? If it’s an emulator device (SCSI2SD, RaSCSI, BlueSCSI, ZuluSCSI, etc), are the settings correct for an internal drive?

For the external drives, all that matters is the very last device is terminated and that none of the IDs are set to 7, the same as another (including same as internal). Every device address needs to be unique, like a phone number is unique.

You cannot hot swap anything. Don’t plug out or plug in any drives that are on or the machine that’s on. Only plug / unplug when all devices are off. You cannot change ID numbers while on, either.

Your last drive in the chain should look like either of these two:

6F173D83-E80D-46F4-9E39-3063DEAC4FD6.jpeg
6C1F7704-F052-4AE2-97C0-7DC24E6C96CB.jpeg


It should never look like this:

4E2D02A5-D78E-445D-85B6-A4604E22F5DF.jpeg
 
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djorud

Active member
Ok, I’m checking this thread while on quick lunch break in the midst of making lefse with the better half. As for the three reasons that can cause the problem, number 2 is most likely the cause. Until I can get SCSI Probe installed, I can’t say whether or not the internal HD is terminated or not. Can it work without being terminated? It does function fine with one external HD. The remaining external HD has been switched from ID “1” to “2” to “3” with no difference in outcome. Until I can see the analysis done by SCSi Probe, I’m still blind to what is going on. It’s on floppy now, ready to be dragged over to the system folder on the CC. Maybe later today will have an opening in the routine here to get that much done…
 

Phipli

Well-known member
Ok, I’m checking this thread while on quick lunch break in the midst of making lefse with the better half. As for the three reasons that can cause the problem, number 2 is most likely the cause. Until I can get SCSI Probe installed, I can’t say whether or not the internal HD is terminated or not. Can it work without being terminated? It does function fine with one external HD. The remaining external HD has been switched from ID “1” to “2” to “3” with no difference in outcome. Until I can see the analysis done by SCSi Probe, I’m still blind to what is going on. It’s on floppy now, ready to be dragged over to the system folder on the CC. Maybe later today will have an opening in the routine here to get that much done…
SCSI probe just tells you the ids and manufacturer / product. Nothing about termination.

Try switching one of the drives to id 6 first.
 
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