turning 32 bit addressing off

32-bit addressing is always on in Mac OS 7.6 and newer. If you start up a computer with 32-bit addressing turned off into Mac OS 7.6 or above, it will turn it on and immediately restart.

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According to the technical specifications, a Performa 575 is (at least as far as hardware is concerned) capable of working with either 24 or 32 bit addressing. You may want to try an earlier operating system, perhaps the downloadable System 7.5.3 (US version here).

Jan

Virtual Memory requires 32-bit addressing to work. Don't know if you have VM On or Off. If it's On, turn VM Off & see what happens. It's a long shot.

 Cheers, Tom

Tony,

saw the Performa 575 was 32 bit addressing.

The aforementioned technical specifications page lists both 24- and 32-bit addressing. This, usually, means that (with the proper system software) you have a part of the Memory control panel with a choice between 24 and 32. Compare this to, for instance, the PowerBook 190cs, where only 32-bit addressing is mentioned (in this case the Memory control panel even under System 7.5.3 does not contain the segment where you can change the addressing mode).

do you think that the IIe card would have a good chance to work with the 7.5.3 OS?

I am not familiar with the card in question, but System 7.5.3 might at least offer the possibility to switch between 24 and 32.

If you want to test an earlier system, it is not absolutely necessary to remove the existing 7.6.1. You could download and copy the nineteen 7.5.3 files to the Performa 575 hard disk. Once there, use StuffIt Expander to decode the .bin files. Place the decoded (one .smi and eighteen .part) in a common folder. Now, use a separate boot floppy (e.g. the Network Access Disk 7.5 here) to start the computer. Change the name of the existing (7.6.1) System Folder on the hard disk (call it 7.6.1 System Folder), and move the System suitcase out of that system folder (place the suitcase in any other folder on the hard disk). Next, double-click on the first 7.5.3 file (.smi); this will mount the total disk image. You will find an installer inside the mounted image. Install System 7.5.3. Restart.

Whenever you wish to return to System 7.6.1, rename the now active (7.5.3) System Folder (call it 7.5.3 System Folder), and move the (7.5.3) System suitcase out. Then, rename the 7.6.1 System Folder (call it System Folder), and move the (7.6.1) System suitcase into this System Folder.

Jan

Tony,

I sing the same song over and over again but people forget the external SCSI port. If you have an external hard drive with a back up system folder, turn off the computer, plug in the drive, turn on the computer, go to control panels, pick the external hard drive as the boot drive and restart.

It is so easy to boot from external hard drives that every one with an old Mac should have a zip drive or other external drive that lets them boot from older systems for repair/diagnostic/restore purposes.

An older system on a Bootable CD or Zip Disk or HDD will solve all your problems.

Ji˜m

Tony,

If that built in Zip drive on the G3 is a SCSI drive and not an IDE interface, you can find an old CD-ROM drive and cable at a thrift store for $5 and swap out the guts to give you an external case for the internal Zip.

You can install a backup copy of 7.5.3 on a zip disk. You can have different systems on different zip disks. Even OS 8.1 will fit on a zip if you leave off the file conversion software. Good luck.

Ji˜m

Tony,

Nice solution. Using the original operating system is possibly better anyway. Not sure whether at all applicable here, but with a PowerBook 140 (another processor et cetera) I once noticed a certain disk-related error with 7.5.3 and 24-bit addressing, while it worked well with 32 (System 7.1 was OK in both modes).

Jan