View Full Version : Frankin Power Mac G5????

Sep 17, 2009, 10:53 AM
Any have experience mixing a 2.0Ghz and a 18.Ghz CPU in a G5? The reason I am asking is because I had 1 sporadic CPU (dual 1.8Ghz) and I wanted to get it back to being a dual system since as a single G5s are slow as molasis. So I ordered a 1.8Ghz CPU off of apple components that was listed as one that was compatible with the RDU code 1.8s. It just arrived and I looked at the code which was QJL which I didn't recognize and wasn't listed as being compatible with my CPU. So I looked it up on their website and it comes back as a 2.0Ghz CPU (and other websites too).

So I plugged it in figuring "great, now I gotta return it because it wont recognize the second CPU". So I turned it on and just figured it would show me single 1.8Ghz G5 in the profiler. It started up and the fans were going wild as expected, but when I checked it shows dual 1.8Ghz CPU. And activity monitor is showing me 2 CPUs right now.

So does anyone know if you plug a 2.0Ghz into a 1.8 system if the 2.0 throttles down to a 1.8 and works anyway? The other thing I figured was maybe the heatsink was damaged and they replaced it with one from a 2.0 (it is actually a little crooked)... but that doesn't make sence because both the sticker on the heatsink AND the daughter card are the same and say QJL. Anyone have any ideas?

I still have to test it for the whole day though. The bad CPU would work fine for the first hour of being installed and then 50% of the time fail to boot up and the other half it would freeze and kernel panic after 2-5 minutes of being on. Switching CPUs (running 1 at a time) seemed to confirm it was the CPU and not the motherboard or the socket.

Sep 17, 2009, 11:11 AM
I have not tried this scenario and I'm a little surprised it worked. Be happy that you have it running again. Obviously the 2.0 CPU is throttled as you say and this would indicate indeed that the old CPU was faulty and not the logic board or power supply. Your problems anyway are typical for failing CPUs.

The heat sink is no problem at all if it fits mechanically. All these systems are designed to huge thermal tolerances and if you have fitted the daughter card properly to the heat sink with thermal grease you should have no long term problem except that another CPU may fail at some time. IBM had an unreliable fab process for the PPC970 and PPC970FX. Many of these CPUs do not reach life expectancy of other typical PC CPUs.

Sep 17, 2009, 11:25 AM
Thanks for the quick feedback.

I have confirmed that it is in fact a 2.0Ghz CPU. I am running the thermal calibration right now and am typing on my Mac Pro. I checked the hardware info with the service diagnostic tool and it looks interesting.

Both CPUs show maximum speed 1800Mhz and bus speed 900Mhz, but where the 1.8Ghz shows frequency high and low as 1800Mhz and 1310Mhz respectively and bus speed high/low of 900/655Mhz, the 2.0Ghz shows high and low as 2000Mhz and 1310Mhz respectively and bus speed high/low of 1000/652Mhz.

So if one of your 1.8Ghz CPUs dies and you have a 2.0Ghz laying around, so long as it is the same revision (in my case version 2) it will work just fine... at least so far it is.

So they did indeed give me the wrong part, but it does the same job. The problem for them is that they were selling the 1.8 for $99 and the 2.0 for $199, so if they had labled it properly they could have made more cash (though I wouldn't have bought it). I think I am justified in keeping it as they made the mistake of misreading it and they don't have any 1.8s left to send me, so their error would be a huge inconvenience to me. If I returned it though it would be a full refund plus I would not accept paying for return postage.

Here are the photos. CPU 0 (device ID 2) is the 1.8 and CPU 1 (device ID 3) is the 2.0.