Problem with Gigadesigns processor

[indibil]

Hi, I'm writing because I'm not sure what happened.

I've had a Gigadesigns 7447@1.6GHz for a while now, which is actually a 1.25GHz processor OC to 1.6, from the factory; I haven't overclocked it. The Vcore is set to 1.3V.

It's been mounted in a GE for a while now, and today I wanted to run tests on a QS because the bus is at 133MHz. It worked perfectly, and when I was done, I disassembled it and remounted it in the GE.

It didn't work anymore, no chime. I remounted it in the QS and it still doesn't work.

I removed the heatsink to measure the Vcore, and when it started up, it was at 1.3V, and after a few seconds, it started to drop to 0.5V. I was like that for about 20 seconds when I tried to touch the CPU to see if it was hot, and I burned myself! It was scorching hot.

Does this mean the 7447 chip has burned out? Could it have happened after shutting down and changing the computer? @herd, you have a lot of experience with processors. Has something similar happened to you before? Do you know what could have happened?

Thanks.

 

[herd]

I would say that CPU needs a heatsink. Putting a bunch of power into a small area without cooling can quickly result in destructive temperatures. Consider how your soldering iron works. If you want to poke around on a running CPU board you could use a water block. These can be small and still sink a LOT of power:

 

[indibil]

I would say that CPU needs a heatsink. Putting a bunch of power into a small area without cooling can quickly result in destructive temperatures. Consider how your soldering iron works. If you want to poke around on a running CPU board you could use a water block. These can be small and still sink a LOT of power:

Thanks for your reply, but it wasn't working before I removed the heatsink. As I explained, it stopped working when I switched from one computer to another, and I can also measure the VCore dropping from 1.3V to 0.5V, as if the processor were short-circuiting. The computer won't boot, there's no chime, no LED, but the chip is at burning temperature.

I have not modified either Vcore or PLL, I have used it with the factory settings.

 

[herd]

I don't think 0.5v is enough to run the CPU. What is the voltage when the CPU is not burning/scorching?

 

[indibil]

I don't think 0.5v is enough to run the CPU. What is the voltage when the CPU is not burning/scorching?

As I mentioned in the first post, the processor is at factory settings, set to 1.3V. I didn't make any changes. When I turn it on, it doesn't boot, there's no chime, no LED, and the Vcore slowly drops to 0.5V. I don't lower it; something exceeds the regulator's power consumption, and it drops.

Yesterday afternoon, I replaced the factory 7447@1250 with a 7447B@1500, and it's working again.

I assume this CPU was overused in the past, and something burned it out, even though the Vcore was only 1.3V.

 

[herd]

... and the Vcore slowly drops to 0.5V.

This sounds like the CPU is melting down and the power supply is going into a current limit or short circuit protection mode.

I'm glad you got it fixed; thanks for following up on your progress.

 

[Forrest]

Check the electrolytic caps on the Gigadesigns board - they may be bulging or leaked.