• Hello, Guest! Welcome back, and be sure to check out this post for more info about the recent service interruption and migration.

Quadra 700 ONLY boots with PPC card installed

aapl2c

Member
Hello!

I have a strange failure. One of my Quadra 700 systems won’t boot, turns on but no boot beep, no video, doesn’t try to boot off floppy/SCSI. It behaves the same when all RAM/VRAM is removed and when trying with a different known good CPU or power supply. The board is in very good shape and I don’t see any obvious physical issues on it.

On a whim, I decided to try an Apple PowerPC upgrade card in it, and it booted right away, playing the PPC boot chime (that card had never been installed in this system). It continues to boot and seemingly work fine if that PPC card is installed…

Since the PPC card has it’s own ROMs on it, I’m guessing there may be some issue with the ROMs on this system (no idea why though).

My understanding is that this system will either use the onboard ROMs or automatically switch to ROMs in the ROM SIMM slot if one is installed. So just for kicks, I installed the ROM SIMM from a IIsi to see what it’d do - it behaved like before, no boot beep/no video/etc. I didn’t expect it’d boot, but was hoping it’d at least play the boot crash chime or something.

Anyone ever hear of a problem like this? I have checked voltages while the system is running in the bad state (seems to be ok) and have probed about with a logic probe and it seems like there's activity on the ROM chips, other places. I'm curious if anyone has more info on what parts of this system controls that ROM muxing (I'm not aware of any schematics available for this)

Thanks!
 

Attachments

  • q700.jpeg
    q700.jpeg
    5.6 MB · Views: 21

linear

Member
that does seem like it could be an issue with the ROMs, but i am not sure what could have caused such an issue.

the ROM SIMM from a IIsi will not boot this system. you will need one that is for a Quadra. i am not sure if those exist as manufactured by apple; if not, you would need to write an image taken from Quadra onto a programmable ROM SIMM.
 

BadGoldEagle

Well-known member
What linear said. Here’s a compatible SIMM (the seller will flash it for you).
- Here's a modded ROM file from bbraun (RAM Check disabled), and the webarchive version;
- The official one from Apple.

I guess there could also be something wrong with the board itself. Is the 040 completely disabled when the 601 is installed? What happens if you use the 601 control panel to switch back to the 040?
 

aapl2c

Member
I'm guessing the way the PPC card works, it disables the 040 CPU. When you (normally) set the control panel to use one or the other CPU, it requires you to power down the system and cold boot.

What's interesting here, this board has no PRAM battery and when you first install the PPC card, it boots right up playing the PPC card's ROM boot chime (different than the 040 68K one) and the control panel shows the PPC card as off. I set it to on and then off again, shut down the system, and tried to cold boot (all the time with power still attached, thus like having a PRAM battery). The system then would not boot, acting like it does when there's no PPC card installed. I unplugged power, let it sit for about a minute (thus clearing PRAM), and then it boots right away off the PPC card/ROM.

Just for kicks, I tried the IIsi ROM in my working Quadra 700 board (again, I know it won't work, but curious of the behaviour). It didn't boot, no boot beep, no video, etc. I then installed the PPC card, and it still wouldn't boot.

Normally you have to go into the control panel to turn on the PPC to use it. The way this bad board is behaving, it seems like it's stuck thinking either the ROMs are bad, thus allow the PPC card to work with priority (maybe some sort of fallback case). Or maybe the ROMs really are bad..

Since there's no schematics for a Q700, I've been looking over the most similar systems like this that there are some available for, the IIci and Quadra 840AV. The IIci has a jumper on it to control whether a ROM SIMM is installed while the 840AV behaves like the Q700 where it "detects" the presence of an external ROM SIMM via logic. Unfortunately, matching pinouts between these 3 systems isn't really clear.

I might just buy a ROM (thanks so much for that link!!) so I can at least in theory rule out the system's ROMs just having gone bad (not sure why).
 

Yodd

Member
Have you been able to resolve this? I have a new to me Quadra 700 behaving the exact same way.
 
Top