Adding External Mass Storage to Your System 6 Mac

In this final and long overdue post on System 6, we will look at adding external mass storage to your System 6 Mac, typically a crucial element in loading application software onto it. After all, you won’t get far with 800K floppies!

External Zip-100 AppleCD300e Larger Set of Floppies

There are several types of mass storage you could choose to add: external hard drives, removable drives, CD-ROM drives, tape storage and so on. All of these are supported by System 6 and are viable options. However, we are going to focus on the two of these that I believe offer the most versatility: the Iomega Zip drive and the CD-ROM drive. Both are still readily available today (if only on eBay). The CD-ROM drive offers a standard media format that a great many programs are distributed on, and the Zip drive offers 100 MB of read/write storage – fundamentally a “super floppy” (this WAS part of the marketing literature for it, way back when!).

I am going to approach this article in the same way as I approached the work: I started with the Iomega Zip drive and then added the CD-ROM afterwards.

External Zip-100

You will of course need both hardware and software to accomplish mass storage for your System 6 Mac. The software of course is freely available on the web, but the hardware will set you back a few pennies. For System 6 Macs, you will want to restrict yourself to SCSI-interfaced Zip 100 drives, and similarly, SCSI-interfaced external CD-ROM drives. As of this writing, SCSI Zip 100 drives are still in abundant supply on eBay, running anywhere from $50 to $100 depending on the seller and the condition of the drive. For the CD-ROM drive, I would attempt to purchase an Apple CD 300 drive, for the simple reason that the drivers are easy to get and are known to be compatible with System 6. You can of course chose different hardware, but you will need to ensure that you also find System 6 compatible software for your drive.

From a software perspective you will need the Iomega Zip driver, v4.2.This can be picked up at Unfortunately, it is not yet out on Happy Macs Gopher site. I have a whole System 6 section that has yet to be loaded! For the CD-ROM driver, you will need Apple CD-ROM Software, v5.3.1. This can be found at the Mac Driver Museum, By the way, you can also get the v4.2 Zip driver here, so this COULD be your one-stop-shop.

Alright, with the preliminaries out of the way, lets get started! For all of this work, I used my (by now) trusty Mac IIsi, running System 6.0.8.


I started by connecting up my external SCSI Zip 100 drive and restarting the machine, just to establish that nothing happens until the driver is loaded. Sure enough, nothing happened! Zip disks, when popped into the drive, were roundly ignored by my Mac. So far, so good. Now I copied the Zip 4.2 driver (a single file) into the system folder and restarted. The restart was clean and Zip disks, when inserted into the drive, now popped up on the desktop as they should. In this case, I inserted a disk labeled System6Exchange, and you can see it mounted on the desktop image below. Well… that was too easy!

ZIP Mounted

… and it stayed that way. Using Iomega Zip drives with your System 6 Mac is incredibly simple. Just connect the drive, add the driver to the System folder, restart, and all is well. This is software the way software should be! Try doing this with a Windows 3.1 PC of the day! It would take days of fiddling to get this right, starting with the nearly Herculean task of getting a SCSI card into the system and running. Take it from me, System 6 Macs were way, way easier to work with than their PC counterparts. I have experienced this from both sides. I was a PC user at the time, and it was a nightmare to add new hardware to a PC. Remember the old ad? Macintoshes were “plug and play”, while PCs were “plug and pray”? 🙂 It wasn’t just clever advertising – it was TRUE!

So now you can read Zip 100 disks on your System 6 Mac. Great! But how do you load anything interesting onto those disks so that you can use them to transfer software and other data onto the Mac? Zip 100 drives are largely a relic of history now, but happily, historical relics remain in abundant supply on eBay. Even given that however, the long and the short of it is that you will need another vintage Mac to write anything useful onto those Zip 100 drives

There are two approaches here. For the first one, you can physically transfer your existing Zip 100 drive to another vintage Mac that supports a SCSI termination, and then load a Zip disk from there. In my case, I have another SCSI Zip drive on my Power Macintosh 7300/200, and I used it to load software and images on to a Zip 100 disk, which I then loaded into the Zip drive on my System 6 Mac. This let me load up my Mac IIsi with software, up to 100 MB at a time.

As a second approach, you can purchase a USB-interfaced Zip 100 drive and use it to load a Zip disk from a USB equipped Mac. I do this as well from time to time. The very PowerMac G5 upon which I am composing this post has a USB Zip 100 attached to it and I use it to load Zip disks routinely. You can see this setup below:

Powermac G5 Dual w Zip

I do not believe that you could plug a USB Zip 100 into a modern Mac and have it work. If any reader tries this and it works, please let me know. My limited work in this area, posted to this blog on July 1, 2013 in the article “Mac OS Standard is Not So Standard” suggests that you cannot write Zip disks in the Mac OS Standard disk format required by System 6 with a Mac running anything beyond Mac OS X 10.4 Tiger. So, I am pretty sure that you will need a vintage Mac to implement even this second approach. If you should find differently, please do let us know!

OK! Onto getting a CD-ROM up and running on System 6. I had quite a bit more trouble with this one, although the outcome was eventually successful. To save you quite a bit of frustration, let me cut to the chase. Before you start down the CD-ROM trail with System 6, you need to add an obscure extension called Desktop Manager to your System folder. This was the key breakthrough in my efforts to get CD-ROMs running on my Mac IIsi. The ever-helpful Macintosh Orchard site, from which you can download Desktop Manager, describes it thus:

“Prevents desktop rebuilds when swapping back and forth with System 7. Allows desktop mounting of CD-ROM. Needed for some file serving apps. Part of AppleShare File Server 2.0.1.”

The key part is that second sentence of course … allows desktop mounting of CD-ROM. After I tracked down and installed Desktop Manager, the rest of was easy.

I am not sure if both of these are needed, but since this is how I approached the task, I will report both. I first loaded Apple CD Setup 3.2, and then when that did not resolve the issue, I loaded Apple CD-ROM 5.3.1.My guess is that all that is really needed is Apple CD-ROM 5.3.1. This is available from the Mac Driver Museum mentioned above.

With Desktop Manager and Apple CD-ROM 5.3.1 loaded, plus a restart, CD-ROMs inserted into my Apple CD 300 drive spin up nicely, and after a disconcertingly long pause, mount cleanly on the desktop. In the screenshot below, you can see both the Zip 100 disk from the steps above and the CD from this step mounted on the desktop.

ZIP and CD-ROM Mounted

When it was all said and done, and with the Zip disk and the CD-ROM together in an external SCSI chain, my Mac IIsi installation looks like this:

Mac IIsi w Zip and CD

Here is an additional “hack” for those interested in trying it. If you have a bootable CD-ROM (in my case a Mac OS 7.6.1 CD), there is a device driver located on track 0 of the disk. This is part of the requirement for being a bootable CD-ROM. If you insert such a CD-ROM into the drive and let it spin up BEFORE you power on your Mac, the Mac’s ROM-based SCSI manager will read and load the device driver from track 0, giving you “software-free” access to the CD-ROM drive. I tried this early in my work above, and after the bootable Mac OS 7.6.1 CD I used had mounted on the desktop, I ejected it and put a different, non-bootable CD into the drive. With the device driver from the original CD still loaded, my Mac went ahead and obligingly mounted the second CD on the desktop too! So, in the worst case, you can “seed” your CD-ROM session with the driver from a bootable CD, and then switch that out for the CD you are trying to work with. Your mileage may vary, but it worked for me.

… and that’s that! You now have both Zip-100 and CD-ROM mass storage up and running on your System 6 Mac. Load away to your heart’s content!