Question about CPU usage for video playback

Question

I've asked a related question already on the Safari forum, but would like some clarification, please.
The speed of this iMac is 400 MHZ and whenever I go to YouTube or almost any other site that requires video I see that the CPU usage can peak way up at 80% or more. I have Flash 9 installed which has a minimum of 500 MHZ, so I get pretty choppy video, but that's not the issue here. I can live with that. I keep any other applications closed. I'm often running a small fan over the top of the iMac to help vent the buildup of heat. I can monitor the temperature at the Hard Drive and I suppose that gives me an idea, of sorts, about general temperature conditions inside.
The answer I got was that this kind of CPU usage could be detrimental to the processor as it builds up excessive heat and to keep this kind of video to a minimum.
My question is can anyone roughly suggest what a maximum time on YouTube, for example, would be, 2 minutes, 5 minutes, is 10 minutes too long? I have plenty of RAM at 768. Some guidelines?
Thanks.

Answer 1

Hey WZZZ,
Thanks for the star and kind words.
I'm the de facto Mac guy at my kids' school and we have around 25 iMac Slot Loaders working there. You can imagine they get abused quite a bit. There are 10 running Garage Band in the Music Department. That puts a tremendous strain on the CPU and I'm actually surprised that they run it so well. My son had a 600 iMac running GarageBand, he was complaining that it was getting jumpy and when I looked at it he was running 10 unlocked tracks simultaneously! So now he has an eMac G4 800 and that of course runs a lot better.
So to sum up, with all the abuse of those machines in terms of the CPUs the problems I have with them have nothing to do with that. The problems have more to do with parts of the OS that they toss, headphone jacks abused, CDs jammed in the slots, and the like.
A couple of other related things. I've got Hardware Monitor, demo, installed and I think it reported it could only find the hard drive sensor, if I'm not mistaken - nothing else on this Mac with a sensor. Is that right?
I see references to CPU sensors on 400 iMacs but on the 400 I have here for repair Temperature Monitor reports no sensors. Perhaps there were different versions of the 400.
But very good to hear that the fan is a good idea for CRT related things. Should I keep the fan running-mostly for that hard core CRT stuff- even if the computer is sleeping and the room temp. is only around 62-64 F.? (We need to put on warm clothes to sit in front of this thing now, but worth it to keep this old machine happy).
On the one I did the fan pushed the airflow in the direction of the passive flow of the iMac - in at the bottom and out the grill by the handle.
One more question, more out of curiosity than anything else: If I move this small clip-on fan close to the case - right now it's about 3 feet away and the image is stable - the screen begins to flicker and flutter quite a lot. My theory is that that's happening not necessarily because of electro-magnetic interference from the fan motor, but rather, because the back of the tube is getting cooled unevenly. What do you think?
Well the classic failures that I see in the iMac are in this order:
1) Dielectric breakdown of the flyback transformers internal insulation. This is heat/age related and a common problem with CRTs in general.
2) Breakdown of high voltage electolytic capacitors and regular high voltage capacitors on the neck board and PAV supply.
3) Solder problems with the flyback itself. This is diagnosed by the upside down boot technique.
I used to repair these problems but now it's easier for me to swap the Firewire boards into working 350s. I've got 12 of those in the basement currently.
Richard