General Info and Requirements

By: Richard Glaser - Revised: 2006-06-14 devin


Overall Mac OS 9.1 appears to be a worthwhile update. Mac OS 9.1 fixes many bugs in previous versions of Mac OS 9 and improves the overall speed and stability. What problems that do exist are mostly minor or involve conflicts with third-party software. Mac OS 9.1 will be required on new Macs and with the final release of Mac OS X. So, in the long-term you may have no choice about upgrading.

Mac OS 9.1 was released on Tuesday, January 9th as a free multi-part download. The original download contained 15 parts for a total of over 70MB. Previous problems with the link not working, or being unable to get through, have been resolved.

Update or Full Install?

If you have any version of Mac OS 9, you can upgrade to Mac OS 9.1 using the upgrade install CD for $19.95. Or you can purchase the "full" version of Mac OS 9.1 from the Apple Store for $99. (link dead)

NOTE: If you have any of the following Macintosh computers:
  • Power Macintosh 6100 series
  • Power Macintosh 7100 series
  • Power Macintosh 8100 series
  • Power Macintosh 8115
  • Workgroup Server 6150
  • Workgroup Server 8150
  • Workgroup Server 9150
Or if you use a Language Kit, you must order the "full-install" Mac OS 9.1 CD to upgrade to 9.1.

Disk Copy IconMulti-part Mac OS 9.1 Update
To download the multi-part Mac OS 9.1 Update, click here. (link dead)

Disk Copy IconSingle-part Mac OS 9.1 Update
To download single Mac OS 9.1 Update is available, click here. (link dead)

NOTE: The single download is 71 MB. Unless you have a fast Internet connection like a cable/DSL modem or LAN, you might consider download the multi-part update.

CD IconUpgrade or Full Install CD
For more details on purchases a upgrade or full install CD, click here. (link dead)

Up-to-date Info

For up-to-date information about Mac OS 9.1, I would recommend the following web sites:


In order to install and run Mac OS 9.1, you will need the following system configuration:

Classic MacMacintosh
Mac OS-based Apple computer with a PowerPC processor (PowerPC upgrade cards and 680X0 processors are NOT supported).

NOTE: Although Apple notes that "third party PowerPC upgrade cards are not supported," many users have had no trouble installing and running Mac OS 9.1 on CPU-upgraded Macs.

Disk IconDisk Space
150 MB to 250 MB for an easy install (though a universal install can be up to 400 MB) of free disk space, depending on options selected, and drive size and format.

NOTE: Though Mac OS 9.1 installer requires about 320 MB of available hard disk space for installation, the System Folder is only 160 MB after restart." During installation, several temporary folders and files are created. These require more room on the hard drive than just the amount needed to install a System Folder.

For more details see Apple's TIL article "Mac OS 9.1: Hard Disk Space Requirements". (link dead)

40 MB of RAM (32 MB of physical RAM, with virtual memory set to at least 40 MB)

Mac OS 9.1 may be installed as an upgrade to Mac OS 7.5.5 and later versions of the Mac OS. The installer program requires Mac OS 8.5 or later to run, and it is recommended that users startup from the installation CD before performing an installation.

For more details see Apple's TIL article"Mac OS 9.1: Start Up from CD to Install on Original Power Macintosh Computers" (link dead)