Booting OS 9 from RAM disk?

[adespoton]

Hello everyone,
It's been too long since I really messed with the internals of OS 9, but long before that I used to boot System 6 off of a RAM disk.

Seeing as I currently have a G4 Mini with 1024MB RAM, and I never use anywhere near 50% of it, and my OS 9 boot disk only uses up 550MB...

Anyone know of a way to get OS 9 installed and booting on a RAM disk?  Any particular RAM disk to use for this?  Or is it just not possible anymore, as the RAM gets wiped at reboot and isn't presented to the EFI partition as a potential disk?

Since OS X boot CDs do it, it seems like it *should* be possible, but it may require some EFI tinkering.

Thoughts?

[IIO]

EFI in old world macs? booting from a RAM disk? RAM is usually not present before you boot.

however, the boot process of MacOS Classic kind of contains that some stuff is read from a mounted image in a form, but there are people here who can explain that better than me.

OSX is another story. OSX can boot into darwin and then do stuff.

[darthnVader]

Hello everyone,
It's been too long since I really messed with the internals of OS 9, but long before that I used to boot System 6 off of a RAM disk.

Seeing as I currently have a G4 Mini with 1024MB RAM, and I never use anywhere near 50% of it, and my OS 9 boot disk only uses up 550MB...

Anyone know of a way to get OS 9 installed and booting on a RAM disk?  Any particular RAM disk to use for this?  Or is it just not possible anymore, as the RAM gets wiped at reboot and isn't presented to the EFI partition as a potential disk?

Since OS X boot CDs do it, it seems like it *should* be possible, but it may require some EFI tinkering.

Thoughts?

PowerPC Mac's use Open Firmware, not EFI.

Only Old World Macs can boot from ram discs, except the Beige G3, it's OW but can't boot Ram Discs.

We lost that ability when Apple started using memory controls they didn't R&D.

Want to boot a Ram disc, use a Power Mac 9600 or older.

[ELN]

Or use David Krauss’s obscure and very clever “Ephemerboot” RAM disk. It checksums the disk image so that it can repaired after the brief cessation of DRAM refreshing in reboot.

I posted a copy on this forum somewhere. I never got it to install, though.

[IIO]

Want to boot a Ram disc, use a Power Mac 9600 or older.

so it can work with OS7.x + ?

can you explain how?

[darthnVader]

I don't think I ever tried with 7.x.x, but all you need to do is open the Memory Control Panel and create a RAM Disk.

The just copy the System Folder and any apps you like to the ram disc, the open the Startup Disk Control Panel and choose the RAM disk and reboot.

[IIO]

i still have a 7300 somewhere, maybe i try that one day. what is the advantage? read faster?

[darthnVader]

i still have a 7300 somewhere, maybe i try that one day. what is the advantage? read faster?

It's about 5x quicker than the SCSI bus.

[Jubadub]

Or use David Krauss’s obscure and very clever “Ephemerboot” RAM disk. It checksums the disk image so that it can repaired after the brief cessation of DRAM refreshing in reboot.

I posted a copy on this forum somewhere. I never got it to install, though.

This?

Looks like the guy behind it did all other sorts of awesome Mac OS programs, too. Absolute jewels like this definitely ought to be archived in the Macintosh Garden. (I may get around to putting Ephemerboot there.)

Now, time to see how this behaves on the Mac mini and MDD.