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

[epoxy2600]

I've got a Quadra 840av with broken SCSI bus - neither internal nor external SCSI devices can mount properly.

I want to install a NUBUS Jackhammer SCSI card that I hope to use for connecting drives.

If I understand correctly, in order to configure the Quadra so that it can boot from an HD connected through Jackhammer, I first need to configure the Quadra to boot from a RAM disk so that I can have System 7.x up and running, run the Jackhammer config software from floppy (which I have) and then instruct the Quadra to use the Jackhammer hard drive as the Startup Disk.

BUT the catch is: how can I set up a RAM disk on the Quadra if the only thing I can currently boot from is a floppy? What I mean is, having a System & Finder on the floppy doesn't leave enough room for the Memory and Startup Disk control panels that I need to set those things up.

Is there a workaround that I'm not thinking of?

 

[Juror22]

Is there some sort of netboot that would be possible?

 

[Macdrone]

finding a scsi cdrom to boot from would fix that rather than floppy, external hard drive or zip to boot from would do the trick also.

 

[BadGoldEagle]

I'm afraid this isn't gonna work Macdrone, as epoxy said SCSI is shot on his 840av.

The internal CD drive on the 840av is SCSI, so it's unusable. 

Only two possibilities left, I'm afraid: local talk/ethernet or floppies...

I'm not sure you can boot from a local talk hard disk. BUT...

Isn't it possible to set up a RAM disk from the 7.1 installer disk? 7.1 will work on a 840av, and that disk is bootable as well.

Edit: Confirmed. With a custom disk (I'm preparing one for you), you can boot system 7.1 (no extensions, only one control panel: memory) from a 1.44 meg floppy.

 

[BadGoldEagle]

Argh. Can't edit my previous post!

Anyway. It's really hard to fit 7.1, system enabler 088 and the memory control panel on one 1.44meg floppy, but I did it. 75K free!! Yay!

It's bootable (tested with MinivMac: You can't create a RAM Disk on a Mac Plus but you should see the option pop up on your Q840 after double clicking on the Memory control panel, from there you should be able to create a RAM disk). 

Be careful though, a RAM disk will be completely wiped out if it looses power... I'm not an expert on RAM disks, but I think a good PRAM battery is necessary.

Link -> https://www.dropbox.com/s/gdwk9n754g5uazt/Custom%20Disk.img.zip?dl=0

 

[epoxy2600]

Thanks Eagle! I will download your floppy and have a go. That's much appreciated! And yes, I have a brand-new PRAM battery I plan to install before proceeding.

I have never set up a RAM disk to boot from. Do you guys think I should do a full System 7.5 install or keep it minimal for my purposes? I suppose a full install wouldn't hurt?

 

[Elfen]

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.

 

[ArmorAlley]

My brother wrote up his master's thesis using a RAM disk on a Mac Plus with 1MB RAM (and no external hard drive, needless to say). He booted up in System 6, created a RAM Disk with a control panel of the same name, copied the contents of the floppy into the RAM disk, altered the startup volume to the RAM disk and did a restart. It booted nicely and he was able to use the freed up floppy drive for MacWrite 5.0 and his thesis.

If you can't get the startup & memory control panel onto the boot floppy, then it complicates matters. I have a JackHammer in my IIfx and I boot from it. FWB has a boot floppy.

I reckon that you should be able to boot from a SCSI drive attached to the Jackhammer, as long as the Jackhammer control panel is present. Read the Jackhammer manual about termination. There are 3 blue pins that need to be adjusted depending on whether you are mixing external with internal drives and/or 8-bit and 16-bit drives. I can't remember offhand, what goes where. I can send you a PDF of the manual if you PM me your e-mail address.

As for workarounds and floppies, I use the Disk Tools 1 from System 7.5.3 and trimmed it off the files I didn't need. It has a smaller System & Finder.

On a final note, internal SCSI went on my IIfx board and it was fixed when I sent the board off to be re-capped. Whether this will work with your machine, I can't say, but I thought that you might like to know.

 

[epoxy2600]

Elfin: you raise a good point. That would be a real Catch-22 if that's true. However, I'm pretty sure you can boot a Quadra from a RAM disk. The instructions that came with the Jackhammer NuBus card explicitly describe setting up a bootable RAM disk to facilitate setting up a sole HD connected through Jackhammer (i.e. boot the Quadra using the RAM disk and then insert the Jackhammer floppy).

ArmorAlley: thanks for sharing the story, I may need to reach out to you for more tips as I set up Jackhammer on my Quadra. Hopefully your IIfx configuration means I can do the same with my 840av.

Eagle: could I bother you to please make another disk image that has the same bootable contents of the previous one you shared, but this time have the Startup Disk control panel instead of Memory? I'm pretty sure both control panels won't fit together, so what I anticipate is first booting from one floppy to run Memory to set up the RAM disk, then re-booting with the floppy with Startup Disk to instruct the Quadra to boot from the RAM disk. After that I can install System 7.x on the RAM disk and see what happens.

Much thanks to all of you for your input.

 

[Danamania]

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.

Your 'if' there isn't a correct assumption - RAM Disks are bootable. You boot off a RAM disk by putting a blessed system folder on it and selecting it in the Startup Disk control panel.

 

[Elfen]

Let me ask you this - and I really want you to think about this really hard...

How is this RAM Disk is being created? It is an actual separate hardware device like this little guy?

http://micha.freeshell.org/ramdisk/

Or is it software. as in it was created with Control Panel -> Memory -> RAM Disk.

The software one like the one created in the Control Panel, will never ever boot because RAM is erased during the boot up and System RAM Test. With the RAM tested and allocated for the system, the OS can boot and fill up the RAM with the system to run on it. The RAM test tells the OS how much RAM is in the hardware and the boot process continues from there.

Question here is - How are you going to boot when your RAM has been wiped clean by the RAM test?

BUT(!!!) If you have a separate RAM Module that is connected to the SCSI and not the motherboard RAM Layout, then you can install it. Hell, I do that all the time with my PCMCIA PowerBooks with such cards:

https://www.amtron.com/sram.htm

They work just as great as CF to PCMCIA cards do; but I only seen this option work for PowerBooks. A branch of this that would work on all Macs is using a SCSI RAM Drive as I stated above.

If you are allocating RAM from your system board to work as a RAM Disk on your system, you will not be able to boot from of it because there is no way to save it from being destroyed by the System RAM Test.

If you got those instructions to do this, post them up and I'll try it on my Quadra 950. If it works, then I'll admit I'm wrong. If it does not work... I'm not here to prove who is right or wrong, I'm just here posting up what I know. And I know this much:

1) Hardware Based RAM drives can boot the system when connected to the SCSI Chain. Their information is not erased when the system is rebooted as their RAM is not part of the Motherboard RAM to be tested. This RAM information stays intact and one can boot off it with set up correctly.

2) Software Based RAM Drives can not boot the system because their information is destroyed during the System RAM Test during a reboot. With this information gone, what is the system going to boot from?

 

[BadGoldEagle]

Yes, I totally agree with Elfen, RAM is supposed to be initialised at every boot up. 

BUT I had a RAM disk on my Mac Portable until a few months ago. The floppy drive was failing, I misplaced the HD and I needed an OS to boot it up. The RAM disk worked fine, until I removed both batteries, that is. Hence my hesitation about power. I don't know how it works on desktop macs.

But then, the Mac Portable isn't really off when it's off, right? So maybe there's some trickery happening letting it save the contents of the RAM disk somewhere on the RAM.

 

[Danamania]

Let me ask you this - and I really want you to think about this really hard...

How is this RAM Disk is being created? It is an actual separate hardware device like this little guy?

http://micha.freeshell.org/ramdisk/

Or is it software. as in it was created with Control Panel -> Memory -> RAM Disk.

It's software, created by making a RAM Disk with the control panel as above - No separate hardware device

If you are allocating RAM from your system board to work as a RAM Disk on your system, you will not be able to boot from of it because there is no way to save it from being destroyed by the System RAM Test.

If you got those instructions to do this, post them up and I'll try it on my Quadra 950. If it works, then I'll admit I'm wrong. If it does not work... I'm not here to prove who is right or wrong, I'm just here posting up what I know. And I know this much:

1) Hardware Based RAM drives can boot the system when connected to the SCSI Chain. Their information is not erased when the system is rebooted as their RAM is not part of the Motherboard RAM to be tested. This RAM information stays intact and one can boot off it with set up correctly.

2) Software Based RAM Drives can not boot the system because their information is destroyed during the System RAM Test during a reboot. With this information gone, what is the system going to boot from?

 

I just did this here:

1. Created a RAM Disk through the Memory control panel (50MB was fine)

2. Copied across a system folder into the RAM disk (I left out things like Preferences, Application Support, and big control panels so it'd fit)

3. Made sure it was blessed (it was)

4. Selected it as the startup disk and 

5. Rebooted

The Quadra rebooted into the RAM disk. The RAM disk wasn't cleared on reboot.

It doesn't work from power off/power on of course, but reboots are just fine.

I've used bootable RAM Disks to solve problems from time to time on Macs and Amigas both. Not for a long while thoughh - I have enough spare parts and machines without having to build  RAM Disks on the fly now, but they can come in handy.

Edit: Screenshot with RAM Disk only, after boot.

 

[BadGoldEagle]

Ok so now we know. Thanks Danamania.

So RAM disks aren't really usable on anything that doesn't run on a battery. But I think you should be able to configure Jackhammer anyway. The RAM disk will be erased afterwards.

And yes, if that Quadra hasn't been recapped yet, please do so before anything else fails. I don't even know how this thing manages to boot, the Mac isn't supposed pass the initial startup procedures without a working scsi chip!

 

[Danamania]

BUT the catch is: how can I set up a RAM disk on the Quadra if the only thing I can currently boot from is a floppy? What I mean is, having a System & Finder on the floppy doesn't leave enough room for the Memory and Startup Disk control panels that I need to set those things up.

Is there a workaround that I'm not thinking of?

I can't remember the details of space on a minimal system disk on floppy, but if you could strip the floppy down a little further and just fit the Memory control panel on, then you shouldn't need the Startup Disk control panel - when the RAM Disk is left as the only bootable device the Quadra should default to booting from it.

Maybe a minimal disk tools floppy with the disk utilities removed and replaced with the Memory control panel to create the RAM disk, then copy that system folder to the ram disk for a minimal boot - and from there start building a full system by copying pieces across from another similar Mac via floppy until you have a networkable config via say, localtalk, to copy the rest of the files across once the floppies get annoying

And then hope for stable power to the 840av while you do it!

Edit: Oops. you already went through most of that with BadGoldEagle. Don't mind me - distracted

 

[epoxy2600]

OK, so I think I get it now:

The RAM disk will be wiped out upon cold boot because of the RAM test, so one cannot have a copy of the System in the RAM disk for practical everyday use. However, if I install the System into RAM disk and then *re-start* (warm boot) then the RAM contents are not cleared and my machine will boot. So I think that's the important distinction.

I looked at the FWB Toolkit instructions closely, and indeed they use the word "re-start" to initiate booting from RAM disk.

I haven't tried anything yet, but will let you know what I find. But based on others' comments here, that's what I'm expecting.

Thank again to everyone for their input.

 

[redrouteone]

Yes from what I recall the RAM contents are only cleared on a cold boot.

 

[techfury90]

This was a commonly-published trick to extend battery life on PowerBooks found in several books, particularly MacWorld Mac Secrets. By running from a RAM disk, you never had to use your PowerBook's HD, thus extending your battery life.

 

[Anonymous Freak]

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.)