Switching Systems on the Fly, or How to Eject Your Boot Disk

[Phipli]

I was playing with a feature I read about, I think in my Mac II manual, a while ago today. I don't remember hearing it talked about much.

In System 6 and older you can switch between running System Folders on the fly by holding Command+Option and double clicking on a non-running Finder. It doesn't reload startup extensions, so I suspect there are functional limits, but it is a handy way of ejecting a boot disk if you need to, or possibly have a system on a disk you want to use and don't want to be disk swapping. Also you can switch to a disk with a different Control Panel set or something.

Sadly, while quickly casting around I could only find almost identical copies of 6.0.7, so... the following is less informative than it could be. But, try it yourself if curious. Be warned that trying to switch to System 7 caused my SE to crash.

Note the disk mount order during the following :

 

[LaPorta]

That is also a known way to switch into MultiFinder if running Finder in System 6.

 

[Phipli]

That is also a known way to switch into MultiFinder if running Finder in System 6.

Interesting, I didn't have a copy of MultiFinder to hand to test.

 

[mikes-macs]

Yes, this is a nice feature in Mac OS System 6. Whatever extensions and control panels that were present and loaded on the boot disk during the initial boot will stay loaded and are available on the "Hot Boot" disk. Furthermore when Hard Disk Drives came out they were very expensive so many computers just had floppy drives. On Macs with enough memory installed, people created a RAM disk and copied their boot-disk system folder to the RAM disk and "Hot Booted" it.
There are CDEVs available that not only create a RAM disk, but they also automate the process of copying the pre-selected items such as a system folder from a hard disk or from a network file server. It will also automate the "Hot Boot" process, eject the disk it came from and on shutdown will copy back the RAM disk system folder to where it came from. As though it was updating the changes. I do this currently from a file server on my network and it works like a charm. The initial boot system folder with all the loaded CDEVs and INITs are on a 1.44 floppy. Everything I need can fit. This includes Network Support. So a 2 MB RAM disk on a Mac SE with 4 MBs of RAM is perfect and there's enough room left over to copy applications from a file server to your RAM disk.

 

[Crutch]

Nice tips. This is properly called a “switch launch”, I believe.