Large Disks in Vintage PowerPC Macs

The main scenarios that have caused me issues with large hard disks in PCI era PowerPC Macs (Beige G3 through to G4 era) are…

1. Many IDE PowerPC Macs from the G3 to G4 era are limited to ~128GB disks.
2. The operating System on some early G3s needs to be in the first 8GB.
3. When partitioning a Terabyte scale disk in Classic Mac OS, Drive Setup fails to allow you to size partitions due to UI issues.

Lets look at each of these issue and solutions individually.

Dealing with the 128GB Limit

I believe this limitation impacts computers from the Beige G3 and original iMac through to some QuickSilver G4s. The issue is caused by the computers only supporting 28bit LBA, resulting in a 128GB limit. I usually aim for a little bit under 128GB as I believe there may be a little bit of margin needed for some reason.

1. The simplest solution, given disks less than 128GB are often more expensive due to so many vintage machines having the 28bit limit (not just Macs), is to get a larger disk such as a 250GB disk, and format it with a 120GB partition in a more modern computer that supports it. This has worked for me in the past, but whatever you do, do not mess with the partition table in your 28bit LBA machine.
2. The next easiest solution, but with a more significant cost, is to buy a PCI card that supports larger disks, such as an after market ATA card, or a SATA card. Note that most cards don’t support Macs, and even some of the ones that do, don’t support booting, only storage. A good option might be a SIL3112 based card as with the right firmware they have Classic Mac OS support (back to System 7.5) as well as some Mac OS X support.
3. Intech Software wrote a special hard disk driver that enabled the use of bigger disks with both Classic Mac OS and Mac OS X (10.2 and later) on the computer’s internal ATA bus. To use the driver with Classic Mac OS, format the drive using their Hard Disk SpeedTools product, but if you want to use the drive with Mac OS X, you will need to install a software driver called SpeedTools ATA Hi-Cap Driver in every OS X install. Note! There are still a number of limitations – it is likely that any computer that suffers from needing bootable OSes in the first 8GB will still need that, so create any bootable partitions you need within the first 8GB. On later machines using this disk driver to use larger disks, they will not be able to boot from beyond 128GB on the built in interface, so ensure that you put a partition divider around 120GB and only use partitions beyond 120GB for storage, and not bootable OSes. There are extensive warnings and guidance in the manuals for this software.

Please note that I’m not overly familiar with the limitations on older Performa 630 -> 6500 family IDE implementations. I have attempted to put a 120GB disk in a 630 but had odd, intermittent write errors. This is an ongoing project and I hope to find out what can and can’t be done with that family of machines.

Keeping the OS Within the First 8GB

Historic understanding of this is that the OS must be within the first 8GB of the hard disk on the Beige G3 and early iMacs, although this has been disputed at times. My personal experience of this is that I’ve had issues over time when I failed to partition a 40GB disk in a 233MHz beige G3 (with a Rev A ROM), but given this was back in something around 2003, I don’t have extensive notes! My thoughts are that more investigation is required with different hardware and ROM revisions to understand what is going on, but in the meanwhile, to be safe…

1. Partition your disk. I usually create a couple of small partitions and then a larger partition, using the larger if I want to run an early version of OSX. For example, I might create a 2GB partition and a 6GB partition for a Classic Mac OS install and a Mac OS X install. Alternatively, I might create two 1GB partitions, a 2GB and a 4GB if I’m experimenting with lots of OSes. I then usually create a single large partition with the remainder of the disk (assuming it is less than 128GB – see above) for applications and storage.
2. Use a PCI SATA or ATA card. Many cards make drives appear as SCSI drives meaning that the host’s ROM doesn’t use the code that prevents booting beyond 8GB (the bug is in the ATA code, and doesn’t apply to SCSI disks).
3. Using a helper partition – given the issue only exists very early in boot, it is possible to use a small helper partition and the software XPostFacto. XPostFacto is able to put a small number of files on a bootable partition, that then hooks into a larger OSX (I don’t think it supports OS9? I’m not sure, please correct me) installation on a large, unbootable partition. This trick can also be used to boot from FireWire drives on machines that don’t support booting from FireWire. Theoretically you could create 10 small partitions within the first 8GB of the hard disk and use each as a helper partition to boot huge partitions later into the disk.

Partitioning Multi-Terabyte Disks Under Classic Mac OS

Note – I believe that you are limited to 2TB disks in Classic Mac OS, but have not personally tested exceeding this limit.

When I installed a 1.5TB disk in my 9600 I found that I was able to format and use the disk using Apple’s Drive Setup, but that if I tried to partition the disk, I could not type in custom partition sizes (my usual trick with a big disk is to use the tab key to cycle through partitions that are visually too small to click on in Drive Setup). After some experimentation with various software, I found that I was able to easily set up partitions, once again using Hard Disk SpeedTools. As such, this is my recommendation for setting up a very large disk (I assume SATA) in a classic Mac OS system.