The Mac Pro First Generation is an Intel Xeon-based workstation computer manufactured by Apple Inc. The first generation model includes the machines from 2006 through 2008.

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8-Core will not boot - Graphic card runs loud and oscolates (cycles)

I have a 2007 8-core MAC PRO. About two years ago, I got rid of the stock GPU and purchased an ATI Radeon HD4890 for it.

All was working well until the other night all of the sudden the fan became very loud and started oscolating (cycling) between loud and less loud. About every second was the pattern of sound.

The system will not boot now. No beeps, errors, etc. The only thing I see is that there are two small LED's for CPUA and CPUB that are on, along with a label by them that says "overtemp". Those are on. If I hit the little reset button by them, I can turn the led's off.

In diagnosing, I purshased another ATI 5770 single card slot and put that in. Still won't boot up. I can also hear a very faint ossolating sound with this card too, but it's definitely not as noticeable.

I've pulled out the card and ram and tried running it. No beeps, etc.

I'm thinking that it might be a bad PSU, but hate to buy one on speculation. Any other thoughts?

Thanks

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I hate stating the obvious, but did you try resetting the PRAM?

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No. Thanks for mentioning that. I'm not as astute with Macs as I would like.

Tried reseting PRAM. No beeps, no nothing. Just out of curiosity, I removed one of the RAM slot cards. This time, the PRAM appeared to reset (chimed twice) and then went to the grey Apple screen. After that, it goes into an infinite reboot loop. Those two pesky red LED's come on the instant that it reboots for the first time. On the plus side, the fan on the old GPU seems to behave now, so it's definitely not that.

I then pulled the first RAM card and put in the second one. Same issue with infinite booting loop. So I put both RAM cards back in and the original issue reappears with no booting and a rapid cycling GPU fan.

RAM card #1 has 2-512mb, and 2-4GB modules

RAM card #2 has 2-512mb only.

I then put both RAM cards back in, but this time removed the two 512mb sticks from card #2. System wend into the infinite boot loop again.

It appears to be RAM related, but then again, not. Hmmm....

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Just a moment ago, I re-attached the DVD drive (removed while I was testing) and successfully booted to my desktop for about 10 seconds at which point it started the reboot loop. :(

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Before you try anything that I just sugusted, try and boot the computer with the clock battery (I believe it's on the motherboard) removed.

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Chris,

I think you're right. I can boot up to the desktop now for at least a minute. Haven't tried longer than that until I do more of a cleaning. Seems that the CPU fins were rather clogged up. I blew them out which seemed to have helped. I'll do a more thorough cleaning today and see how long she stays running!

Thanks all for your help!

Dave

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It sounds like the computer is overheating (Or even worse, thinking it is overheating) Check that the system fans are all working, and maybe remove the CPU heatsinks, and clean them out. Also, replace the thermal compound on the processors if you can. Powermac G5s would act up if one of their processors died, but still show some signs of function. If CPUA works, but CPUB is damaged, you may be able to boot the computer with only CPUA installed. (I would only try this after ruling out any other problems) Unfortionatly, I'm not incredibly familiar with these machines. The RAM wouldn't all die at once, so that probably isn't your problem.

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Most Helpful Answer

You can resolve many system problems by resetting the logic board.

There are three reset switches on the logic board that you can use to troubleshoot

various issues:

 SMC reset: If the computer is experiencing a power issue, resetting the

system management controller (SMC) may resolve it.

 RTC reset: If the computer is experiencing a booting issue, resetting the

Real Time Clock (RTC) may resolve it.

 System reset: You can use this switch to determine if a computer that

won’t consistently boot from a cold start has power supply issues. located in the upper

right-hand corner of the logic board

What are the diagnostic LEDs telling you? The LEDs are located toward the rear of the logic

board, under the memory cage, next to PCI card slot 1. You can view these

LEDs by removing the computer’s side access panel and looking through the

memory cage to the logic board below.

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I ended up having to send it in to have the logic board replaced ($600 repair). Not too happy, but that's life I guess.

Dave

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I had the same symptoms, it was a USB3 hub, when i removed it the Mac worked fine, don't know why it worked a few times before doing that though.

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David will be eternally grateful.
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