Using a Zip 100 drive with a compact Mac

[bigmessowires]

I'm having trouble getting a couple of compact Macs to recognize a Zip 100 drive on the SCSI bus. Forget about driver problems or formatting questions-- I can't even get that far.

I tried this first on a Mac SE/30. Set the Zip drive's internal termination to ON, and id to 5. Both SCSI Probe 3.3 and Lido 7.56 see nothing on the SCSI bus, and also both tools report that the SCSI bus is unterminated. I then tried all permutations of SCSI id and termination ON/OFF with the Zip drive, to no avail. Tried it with and without media in the Zip dirve. I also tried disconnecting the internal hard drive on the SE/30 to see if that was a factor, but no go.

This is the same SE/30 whose hard drive recently disappeared from the SCSI bus, so maybe it's got a motherboard problem. So I also tried it on my Mac 512K that's been upgraded to a Plus configuration, with the same results. I also tried rebooting with the Zip connected and media in the drive, and the drive activity light never comes on, which I'd except to see as the Mac searched for a boot volume. When I insert a Zip disk, the drive activity light does come on briefly, but that's true even when it's not connected to the Mac.

Is there something obvious I'm missing here? It's been a long time since I worked with any SCSI devices. Why would the tools say the SCSI bus is unterminated, even when the internal termination switch is set to ON? For whatever it's worth, I'm using the Iomega-supplied DB-25 to DB-25 cable to connect to the Zip drive.

A friend of mine bought the identical setup from the same source for his Powerbook 170, and he can't get it to work either. So I think we most both be doing something dumb.

 

[bigmessowires]

I should add: both SCSI Probe and Lido report that the SCSI bus is unterminated even if the Zip drive isn't connected at all. So maybe that's just a generic error message they report when no SCSI devices are detected?

 

[kite210]

IIRC, you need an extension to use a Zip100 drive with a mac, but don't quote me on it.

Here is a link with a download for the driver and tools needed Here

It also has helpful instructions on how to get the drive to connect.

Just don't quote me on it, I've only used a zip drive on a PowerBook G3 and a Power Mac G3, so I'm not sure if it could be the same problem or not.

 

[bigmessowires]

Thanks. I'm attempting to follow a similar set of instructions for the Zip setup, which rely on Lido's driver instead of the default Iomega driver: http://www.vintagemacworld.com/pluszip.html

But either way, it's my understanding that the device should always show up on the SCSI bus, regardless of the driver, and a missing/broken driver would just cause problems mounting and reading the disk. And since I see nothing on the SCSI bus, maybe something more fundamental is broken. Regardless, I'll try the Iomega driver method you linked and see what happens.

I should also mention that this is all being tested under System 6.0.8.

 

[bigmessowires]

I crammed the Iomega 4.2 driver onto an 800K System 6.0.8 startup floppy, and tried it on the 512K with the Plus upgrade. The extension won't load-- it shows an X through the extension icon at startup. I can't try it on the SE/30, since while debugging the Zip drive problem, the SE/30 mouse somehow broke. I think this just isn't my day.

Still nothing on the SCSI bus-- also tried the Mt. Everything control panel. So I am truly stumped, as several online guides say this drive should work with a Mac Plus.

 

[Trash80toHP_Mini]

Look for the "Iomega Guest" application. That''ll usually work when drivers don't.

 

[bigmessowires]

Well, I give up. There are many online guides for using a Zip 100 on a Plus, and I'm doing exactly what they say, but the drive is never detected by any SCSI utility, so the whole question of drivers is moot. I have to conclude that my 512K with the Brainstorm memory+ROM+SCSI upgrade is somehow not exactly equivalent to a real Plus, causing it to not work. Seems very fishy, though.

I have a real Mac Plus coming in the mail in a couple of days, so I guess I'll try it with that.

 

[coius]

Keep in mind some systems don't provide Term Power, and your Zip 100 doesn't. Without Term power (terminator) it won't show up as there is nothing to provide active termination. You might need a hard drive or an external Terminator that can provide it's own power (by say a 5v wall-wart). I found this out with an Apple //e w/ SCSI Card (Apple High-Speed SCSI) and also a PowerBook 145b that doesn't provide term power.

iirc, some early machines omitted term power if they didn't originally ship with an internal SCSI drive.

 

[PowerPup]

I'm planning on getting a Zip drive for my Classic II one of these days.

Anyway, here's some info on using Zip Drives on Old Macs:

Mac Plus and Zip Drives Revisited (I'd recommend reading this one first, it has some useful info on driver issues.)

Using A Zip Drive On A Mac Plus

Mac Plus and using a zip drive as a hard drive (Apparently, some of the Plus ROMs possibly had SCSI issues.)

Click-Death Fix Guide (... Just in case.)

Hopefully there is something useful among all that data.

Edit: Oh Hmm, well. Coius could very well be right. Considering that your 512k has third party SCSI.

 

[bigmessowires]

I'm starting to think maybe I do have a problem with termination. I don't really understand how "active" termination is different from passive termination, and which one is required. Are you saying that setting the Zip 100 termination switch to ON is insufficient? I have essentially the same problems trying to use this drive on an SE/30 and a Plus, so I don't think it's a Plus-specific problem.

PowerPup linked a great, three-page thread from 2007 from someone who was having similar problems with a Zip on his Plus. Eventually he got it to work, but unfortunatley he never explained what the solution was.

I have tried both the Lido-format method described at http://www.vintagemacworld.com/pluszip.html as well as the Iomega 4.2 driver method described at http://www.jagshouse.com/zipMacPlus.html. With the Iomega 4.2 driver, the driver extension icon appears with an X through it during startup, so something is wrong. This is true on both the SE/30 and the Plus, under system 6.0.8.

 

[phreakout]

SCSI termination is all apart of the so-called SCSI voodoo. Having too little or too many terminators installed causes the entire chain to not work properly. In my experience, I've had good luck by adding a SCSI terminator cap to the end of the chain, along with making sure termination was enabled on the external device via its switch. Also, make sure the device's ID is set to 6 (if you can change it) and that it's powered on, before turning on your Mac. The Iomega v4.2 driver should work with that drive and cartridges as well.

73s de Phreakout. :rambo:

 

[coius]

To terminate the SCSI bus, the Terminator packs (whether part of a device, or a block itself) must have power (I think it's +5v) in order to properly terminate the bus. When there is no power, it's as if the terminator is not even on the chain. This causes the signals to bounce back and forth causing the noise on the bus to go higher and higher really quick drowning out any signal. This is why it's important to have power on the SCSI bus for termination.

Most of apple's newer machines could do this, some didn't (I don't think the PowerBook 145b did, since mine required a SCSI HDD to provide the power), most do. A lot of older SCSI cards back when SCSI-1 standards weren't totally set, people deviated so widely, that the SCSI Voodoo was even worse, and it was like pulling teeth to get things to work right, and depending on which shoulder you threw the salt over, good fortune might smile on you and the SCSI keeps working.

Apple especially followed this, integrating this and that, while leaving out other things that they didn't want to/feel the need to implement. Some of those were the Term power.

Since a lot of hard drives back then supplied it (external drives I mean) it wasn't much of an issue, but when several manufacturers thought "Why do we have >x devices putting power on the bus?" they pretty much stopped that. I have several 68-pin and 2 80-Pin SCSI drives that do not have their own Term power and require the card to do that.

It's quite rare for a modern SCSI drive to ship with it either turned on, or available for that matter, since about 99% of the time, the card provides the power on the bus.

Like I said, if your mac doesn't provide the power, and the Zip 100 doesn't provide the power (no external Zip 100's did iirc) so SOMETHING has to provide power, and lack of that causes issues. That can range from SCSI drives popping off the bus, to crashes (Random signals locking up the bus, or noise) or plain not showing up in the first place.

I would suggest, if you have another SCSI drive, possibly from another mac, Attach it inside the SE/30, or take the one you have, and set it to provide Term Power. I would be willing to bet that would solve your issue, especially since a lot of apple's shared the same SCSI Bus both inside and out.

Keep in mind, should you need to terminate the bus, you MUST terminate at both ends. This means the drive inside (HDD) and the last drive outside have to be terminated, but NOWHERE in between. Since it shares the bus, an extra terminator would make the signal weak, or not pass through the chain.

I seem to recall that most machines (except the IIfx, which i think is why that special black terminator was used) that apple used provide termination at the card in most cases, not sure on all. So if you had no external drives,a only internal, the adapter would terminate, and the drives inside at the end would terminate.

SCSI Voodoo is weird, but if you sit down and look at it, especially on wikipedia, you will get the hang of getting it all to work together, and be able to make it work 99% of the time.

Another thing you will want to check is cables. on the SE/30, if the cable gets damaged/knicked/etc.. you might be causing issues. You might want to try to find a different cable and use it.

Take the drive out of the SE/30 and look up the jumper settings and make sure "Term Power" and "SCSI ID (anything other than 7, the Apple SCSI adapter uses that)" is set properly. So if you internal drive is set to 7, set it to something like 0 or 1 or 2 or something (I would suggest 1) and make sure the Zip is not set to the HDD.

Connect up. Also make sure the Zip drive is on and ready before you turn on the machine. Some problems with SCSI happens because you bring up the bus before all SCSI drives are ready. So any drives you put on it externally, make sure they are powered on and hooked up before you start the machine, otherwise you can crash/hang the bus.

Try this and see if it works. failing that, read up on wikipedia, whole host of treasure troves of information!

 

[bigmessowires]

Thanks for the detailed reply, it helps. I read up on SCSI termination methods, and it makes some more sense now. Maybe all the people who've used an external Zip 100 with a Plus also had some additional SCSI device with active termination, but just never mentioned it?

I'll take another look at the SE/30 internal drive termination and jumper settings.

One thing I'm a bit confused about: in a single-drive system like the SE/30 with an internal HD, the HD will be terminated and the SCSI controller on the motherboard will be terminated, right? Those are the two sends of the chain. If I then connect an external SCSI device and terminate that, it stands to reason that I'd need to disable termination somewhere else. Would the internal HD mark the other end of that chain, or the motherboard controller? Is there some kind of auto-termination on the motherboard controller maybe? If not, then anyone adding an external SCSI device to a Mac that already contained an internal SCSI HD would have had to crack open their Mac and change some termination settings, which I don't ever remember doing back in the day when these machines were current. In fact I know I added an external SCSI CD-ROM to a Mac SE that had an internal SCSI HD, and I never once opened up that Mac.

I'm beginning to understand why SCSI died off.

 

[Dog Cow]

No, you don't need to open your Mac to add SCSI.

Termination:

A SCSI chain must be terminated at both ends. If your Mac has an internal HD, then that HD should be terminated (unless someone's been fiddling). Then, you just need termination at the last device, which in your case is the SCSI Zip drive. That's what the slider switch does. Switch it on.

However, if the Mac does not have an internal HD, then you need two terminators. This Mac is the Mac Plus. It needs a pass-through terminator connected right into its SCSI port. Then you could connect a SCSI Zip drive, and you'd still set the Zip drive's termination switch.

Other external SCSI devices, such as the Apple CD-ROM drives, don't have this termination switch feature. For these devices, you really do need a terminator block (generally Centronics).

What does termination do? Well, it's supposed to keep the electrical signals from "bouncing" back down the chain and confusing the other devices or your Mac. Some people can get away without using terminators, others don't.

 

[techknight]

think of a radio transmitter.

Using a terminator on a SCSI bus is the same thing as matching your antenna/feedline to your transceiver. Same difference.

 

[bigmessowires]

Thanks. I think you may have misunderstood my question, which is a generic question about SCSI and not really about the Plus. Basically, there must always be two points of termination at opposite ends of a SCSI chain, right? So in a Mac that only has an internal HD, where are those two points?

Now add an external SCSI device to that same Mac. Since it's external, it forms the new end of the chain, and must be terminated. Now you will have three points of termination unless you either manually change something inside your Mac, or the Mac auto-adjusts somehow. Since in reality no manual internal changes are needed, that implies that the Mac auto-adjusts somehow, but I don't know how.

 

[phreakout]

The usual rule of thumb applies:

1.) Internal SCSI drives (most of them) have the SCSI termination already built-in on their controller cards. So you only need to make sure termination is enabled on those type of drives. Usually there's only 1 internal hard drive in each retro Mac, but there are configurations of more than 1 internal HDD, plus add in if there is 1 or more internal CD-ROM drives.

2.) For external SCSI devices, you usually want termination enabled at the beginning and at the end of the SCSI chain. Some devices, like storage drives, are finicky and work best with just a terminator at the end of the chain, rather than adding one at both ends. For this, it takes some trial and error to get SCSI working right.

3.) This regards the SCSI id number assignments. ID #7 is reserved for the Mac itself. Internal hard drives are assigned ID #0 and the internal CD-ROM (if you have one) is assigned ID #3. That leaves you ID # 1, 2, 4, 5 and 6 for anything else you add on. I've had good luck assigning #2 or #6 for external drives. The most critical rule is to make sure you assign a different ID number for each device; you should never assign the same number to 2 SCSI devices or your Mac will crash.

4.) Check the quality of your SCSI cables. Cheaply built cables will have problems with shorting out and also aren't shielded properly; RF interference and other noise can leak in and cause problems sending and receiving across that cable. Also, make sure you use short length cables. Even though the standard is up to 18 feet of cable, you do need to subtract from that figure the length of cable inside an external device's case.

5.) Make sure you turn on your external SCSI devices before powering up your Mac. You might be able to leave unused SCSI devices turned off, but read the manual or test it to see if it can allow pass-through while turned off.

6.) Hook up your SCSI devices in a different sequence in the chain. This can be one way to fix certain problems of SCSI voodoo. If you do this, make sure you move the termination configuration for the end of the chain from one device to the new end device. Don't try to terminate devices in the middle of the chain.

Give this a whirl and let us know how it works for you.

73s de Phreakout. :rambo:

 

[Dog Cow]

Basically, there must always be two points of termination at opposite ends of a SCSI chain, right?

Right.

So in a Mac that only has an internal HD, where are those two points?

Point 1 is the internal HD. Point 2 is the last device on the SCSI chain, which in your case would be the SCSI Zip drive. Setting the Zip drive's switch will enable termination.
To go further, if you were to connect, for example, a CD-ROM drive too to your SE/30, after the Zip drive, you would disable the termination switch on the Zip drive, and use a terminator block on the CD-ROM drive's 2nd SCSI port.

 

[Trash80toHP_Mini]

. . . there must always be two points of termination at opposite ends of a SCSI chain, right? So in a Mac that only has an internal HD, where are those two points?

I don't know the SCSI spec all that well, but it's a well documented general computer interface standard from the MiniComputer era. Theoretically, you should be able to convert USB or ANY other interface to 68k Macs over SCSI.

On the Mac's totally un-compliant SCSI implementation of the SCSI standard things get a bit tricky. I don't know about the Compact Macs, but in many later Macs there's a shrouded MoBo header for a terminator block just inboard of the the external SCSI connector.

This is reversed in the DuoDock, which uses this same setup on the internal side of the SCSI Chain, which allow for an optional internal HDD setup.

SCSI Adaptation for earlier Macs more than likely makes troubleshooting a ClusterChain of significant proportions!

Suggestion:

Active Termination entails adding electronic components for auto-sensing termination of the SCSI Chain, which is entirely different from just having termination active.

I'd suggest sourcing an external peripheral case with the Active Termination Circuitry built into the Dual Centronics 50 Connector/ID Switch PCB to add to the end of your chain.

That's always been my first test for troubleshooting SCSI Voodoo!