CPUA Fail Red Light on Mac Motherboard

Thanks a bunch!!! this helped me after getting CPUA & CPUB fail lights yesterday. the one that did it was replacing the coin (cmos) battery. I think it was due anyway, I am still running a macpro 1,1 since 2006.

I don't think TT Deluxe is all that useful.

Strip your Mac down, and use Apple Hardware Test.

Monitor sensors with Hardware Monitor, set an alert if needed.

Don't run more than one program, fewer is better and you can have too many 'cooks' even for checking drive status.

Note on drives, check out MPG and why SoftRAID 4 should be your main disk check.

Dont rely just on automatic fan control. Doesn't work all that well. Run SmcFanControl 2.2.x with profiles for medium, high, etc you can switch to. Default doesn't do enough.

FBDIMMs are hot, keeping those under 73*C is a must. And watch out that they all register for what they should be.

Do just one SMC Reset and cold PRAM zap.

So no, I would not rely on VRAM test in TTD. If it makes you feel better, upgrade to TTPro 6 but I don't think that is best use of money either. But better.

And to play it safe, order a new graphic card. Sometimes the best way to troubleshoot and rule out, and for $250 I'd say worth it... unless you already have ATI 5770. Good for FinalCut.

There are always things running in the background doing something. Try to eliminate, your system will run better (faster, less lost resources) and more stable. Every last widget, you pay a price. Including SMART monitoring dodads.

I found an old apple service manual that goes with your system. It even showed a picture of the bank of diagnostic leds which you described. Without any additional comment from me, below is what that service manual says for LED 3 CPU A:

LED 3 CPU A (Upper Processor) Error

Normally off. These LEDs come on if an error occurs or if the BootROM is corrupted. They do not depend on the DIAG_LED button being pressed.

Related symptoms include no video or the computer is hung up. If the BootROM is corrupted, the optical drive tray should eject, prompting for the insertion of a recovery disc to restore the BootROM.

Troubleshooting:

• With the computer booted, up press the SYS_RST switch. If this clears the CPU Error LED, check for incompatible device driver software that may have been installed for added hardware.

• If the Error LED is still on, power down the computer and try pressing the SMC_RST switch. Restart the computer.

• Reset the power supply by unplugging the AC cord for 10 seconds.

• Unplug AC cord and remove any added DIMMs and PCI Express cards. If this causes the LED to go off, repopulate the DIMMs and/or PCI Express cards to find the combination that caused the LED to come on. Overheated memory could be a possible cause for this CPU error LED to come on. Check fan operation.

• Unplug the AC cord and remove the battery for 10 seconds. You may need to remove a PCI Express card to get to the battery. Reinstall the battery and restart the computer.

• Try swapping CPU A and CPU B locations. If the CPU Error LED follows the CPU, replace that CPU.

• Try replacing the logic board.

1900s had to be pulled, dust cleaned out, terrible design, every 3-4 months

ATI X1900 XT Artifacts Overheating Notes Tips

So you should already be aware of its problems and ready to upgrade.

There was a recall for some too.

I have the exact same vintage Mac Pro and graphics card, and having the exact same problem. Took it into the Apple store about 2 months ago, nothing apparently wrong. They then found the interior "dirty" and cleaned it out and ran a rather extensive stress test and found all is good. Worked fine, but now the problem is back. I've placed a small fan on the floor outside the Mac blowing into it to see if that helps, but the problem persists. Definately please post what you end up buying to replace the X1900, I am thinking I've got the same problem you have.

1- with the computer on press the internal "sys rst" botton.

2- With the computer off but power cord connected press the internal "smc rst" botton

3- with the computer off but power cord connected press the internal 'RTC RST" botton

if still not booting and still a red ligh inside near to SMC RST botton. unplug the computer ,take the internal coin battery out for 30 minutes and then try again.

dagocast did you notice that the post is almost 4 years old? I do not think the poster is still waiting

dagocast wrote:

1- with the computer on press the internal "sys rst" botton.

2- With the computer off but power cord connected press the internal "smc rst" botton

3- with the computer off but power cord connected press the internal 'RTC RST" botton

if still not booting and still a red ligh inside near to SMC RST botton. unplug the computer ,take the internal coin battery out for 30 minutes and then try again.

lllaass at dagocast----- > did you notice that the post is almost 4 years old? I do not think the poster is still waiting

....but the information is still valuable to people searching info for the same issue 4 years later! ;-) like moi!