How to set up a bootable RAM disk on a Quadra with no SCSI devices?

[techfury90]

I believe NewWorld broke it.

 

[Elfen]

Because there is some confusion - some Macs can make a bootable RAM disk (although it loses its contents if you shut it all the way off,) some Macs can't.  I don't know for sure about the Q840av, I know that most of the Power Macs aren't bootable from a RAM disk.  (Some systems save the RAM disk contents to your primary hard drive on shut down, some don't.)

THAT(!!!) Is the Equation to the problem!

 

[Bunsen]

Q: How can you boot off a RAM Disk if the RAM Test before Boot erases all the information on RAM?

This makes booting off a RAM Disk impossible.

The best you can do here is to boot off a floppy.

I hate to be negative, but no.  Bootable RAM disks are indeed a thing, which I've used, and dozens of us here have used.  You are quite wrong here.

 

[Bunsen]

To OP - other alternatives include

- having someone else with a Jackhammer create a bootable SCSI drive for you, and sending it to you.  (Perhaps a SCSI2SD if you felt like investing in one at this point)
- I *think* BMOW's FloppyEmu can mount a floppy image larger than 1.4MB, if necessary.

 

[Cory5412]

I don't believe that the 840 supports the necessary HD20 emulation for above-1.4-meg images on the floppyemu, unless there have been some updates there I haven't seen.

To be honest, if the floppyemu will allow newer systems to boot off of above-1.4meg images, it might be worth looking into that. (I will probably even do so, because I very much like the idea of being able to use that to transfer data between system 7-era Macs.

As another idle thought... do you have another Mac with NuBus slots and working onboard scsi? Maybe you could create the jackhammer boot disk on your own in another Mac.

Another-nother thought, how much will a bare system even do? Just boot the NAD and use everything over ethernet or serial.

 

[Elfen]

I hate to be negative, but no.  Bootable RAM disks are indeed a thing, which I've used, and dozens of us here have used.  You are quite wrong here.

You're right but that is why I posted what I posted in my last post about it being the equation to the problem. It seems going along with Anomous Freak's post is that some macs support this and some don't.

My findings:

It does not work on my IIfx or SE\30. On rebooting, the Machine goes through a RAM Test and the contents are erased.

It was 50/50 on my Q950. Let me explain.... when I press the Reset Button, it does not work because the machine does a RAM Test that erase the RAM Drive. BUT if I use Special Menu - Restart, the machine reboots without the RAM Test and then the machine boots from the RAM Drive.

I have not tested this on my IIcx, IIci, IIsi or LCIII.

The major problem I see, as in the case of the Q950, if the machine crashes and you need to press your reset button, your machine will wipe out the RAM Disk during the RAM Test.

The Question lies, what machines out there will reboot with the reset button that will not destroy the RAM Disk? From the sounds of it - the Q600 - 800. But I do not have these machines to test this theory.

 

[Danamania]

You're right but that is why I posted what I posted in my last post about it being the equation to the problem. It seems going along with Anomous Freak's post is that some macs support this and some don't.

My findings:

It does not work on my IIfx or SE\30. On rebooting, the Machine goes through a RAM Test and the contents are erased.

It was 50/50 on my Q950. Let me explain.... when I press the Reset Button, it does not work because the machine does a RAM Test that erase the RAM Drive. BUT if I use Special Menu - Restart, the machine reboots without the RAM Test and then the machine boots from the RAM Drive.

I have not tested this on my IIcx, IIci, IIsi or LCIII.

The major problem I see, as in the case of the Q950, if the machine crashes and you need to press your reset button, your machine will wipe out the RAM Disk during the RAM Test.

The Question lies, what machines out there will reboot with the reset button that will not destroy the RAM Disk? From the sounds of it - the Q600 - 800. But I do not have these machines to test this theory.

There's an option in the Memory control panel on some machines that allows you to disable the ram test on startup. Helps with Q950s that have a full complement of RAM.

https://happymacs.wordpress.com/2015/01/30/speed-up-mac-os-boot-time-turn-off-ram-tests/ shows how to do it in 9, It may be the same in earlier ones. I used to turn it off on my 950 as 128MB was minutes-long for a cold boot test.