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OpenBSD 6.2 on an iMac G3 from 1999 (iMac,1)

A while ago I spent $50 for an iMac G3 (aka the iMac,1). This iconic model restored Apple's fortunes in the late '90s. Since the iMac G3 can still boot Mac OSes 8 and 9, I mostly use the machine to indulge a nostalgia for childhood schooldays spent poking at the operating system and playing Escape Velocity. But before I got around to that, I decided to try out the software that the previous owner had left on the machine. The antiquated OSX 10.2 install and 12 year old versions of Safari and Internet Explorer were too slow and old to use for anything. Updating to newer software was almost impossible; a later OSX is required to run the little PowerPC-compatible software still languishing in forgotten corners of the Internet. This got me thinking: could this machine be used, really used, nowadays? Lacking a newer OSX disc, I decided to try the most recent OpenBSD release. (And, since then, to re-try with each new OpenBSD release.) Below are the results of this experiment (plus a working xorg.conf file) and a few background notes.

My iMac G3
My iMac G3 when it was running OpenBSD 5.5.


This iMac is a Revision D iMac G3 in grape. It's part of the iMac,1 family of computers. This family includes all tray-loading iMac G3s. (Later iMac G3s had a slot-loading CD drive and different components.) Save for a slightly faster processor, a dedicated graphics card, and cosmetic tweaks to the case, my iMac is identical to the prior year's line-launching Bondi Blue iMac. My machine has had its memory upgraded from 32 MB to 320 MB. Thank Goodness.

The Revision D iMac G3 shipped with Mac OS 8.5. It can run up to Mac OS 9.2.2 or OSX 10.3.9. Other operating systems that tout support for the iMac,1 include NetBSD, OpenBSD, and a shrinking number of Linux distributions.

OpenBSD is simple (by design) and well-maintained. In contrast, NetBSD seems rather more complex and featureful, and I have heard grumbling that despite its reputation for portability, NetBSD really only works well on amd64. I'd test that assertion if OpenBSD's macppc installation instructions didn't seem much simpler than NetBSD's. Linux is even more complicated, although most distros are put together in a way that you can mostly ignore that complexity (until you can't). In the end I went with OpenBSD because I am familiar with it and because I like it.

Installing OpenBSD on the iMac,1

Installing OpenBSD on this iMac was simple. It's the same procedure as installing OpenBSD on an amd64 rig. You put in the installation disc; you tell the machine to boot from it; and then you answer a few prompts, most of which simply ask you to press enter. In this case, OpenBSD recognizes all machine's hardware just fine, including sound and networking, though I had a little trouble with video.

The OpenBSD documentation says video should just work and that an xorg.conf file isn't necessary. As such, it no longer ships with an xorg.conf file. Though that's never posed a problem on my other OpenBSD machines, it does here. Video doesn't work out of the box on my iMac,1. startx just blanks the screen. Fortunately, because the BSDs use a centralized development model where each operating system is stored in one repository, OpenBSD's website provides a web interface to the source code going back to the early days. I was able to find the last version of the sample xorg.conf that used to ship on macppc. With a little tweaking, I transformed that file into this one, with which video works just fine. Just drop it into your iMac's /etc/X11 directory. You'll also need to remember to set the machdep.allowaperture sysctl to 2 (e.g., as root run sysctl machdep.allowaperture=2), although the installer will do that automatically if you answer yes to the question about whether you plan to run X.

All that being said, video performance is pretty poor. I am either doing something wrong, or OpenBSD doesn't have accelerated video for this iMac, or this machine is just really old! I will discuss performance below.

Running OpenBSD on the iMac,1

The machine performs okay under OpenBSD. You can expect to ably run minimalistic software under minimalistic window managers. I tried dillo, mrxvt, and cmus under cwm and fvwm. Performance here was just fine. I also tried Firefox 26, 33, and 34 under fvwm and cwm. Firefox ran, but "modern," Javascript-heavy sites were an exercise in frustration; the 2015 version of basically froze Firefox for 30 seconds or more. A lighter browser like dillo is doable.

You'll notice that I used the past-tense to talk about Firefox. Firefox currently doesn't build on PowerPC on OpenBSD. Neither does Chromium. Neither do a fair number of applications. But whatever -- there's still a lot of lighter applications available, and it's these you'll use day-to-day on a decades-old machine.

dillo on my
iMac running OpenBSD 6.2-current
dillo on my iMac running OpenBSD 6.2.

Lightweight window managers work okay, as you'd expect. You can even run heavier desktop environments, such as xfce, though you'll give up a lot of performance.

A screenshot of xfce
on my iMac
xfce 4.12 under OpenBSD 6.0-current. It's very slow on a 333 MHz PowerPC machine.

I ran the Ubench benchmark on this iMac and two more modern machines also running OpenBSD. The benchmark seems like an old one; I don't know how (if at all) it accounts for hardware changes in the past 13 years. That is, I don't know if the difference in score accurately measures the difference in real-world performance. Here are the results anyway:

iMac,1 with 333 MHz CPU and 320 MB RAM Intel Atom D525 with 4 GB RAM Intel Core i7 2620M with 8 GB RAM
Ubench CPU 18,058 186,441 999,657
Ubench MEM 9,647 33,643 167,294
Ubench AVG 13,852 110,042 583,475


Except for when I check to see if OpenBSD still works, I run Mac OS9 on this rig. I have faster and better machines for running OpenBSD. If I didn't -- if this rig were, improbably, all I had left, and I was waiting on the rush delivery of something modern -- then I would use OpenBSD on my iMac,1. I'd have to stick to lightweight applications, but at least they'd be up-to-date and running on a simple, stable, OS.