Atari 600XL measures C64 internal case temperatures with/without fan

[Britishcar]

I used a 600XL to measure the internal case air temperature of a C64 while it was searching for prime numbers during a two hour period. Here’s what I discovered.

 

I ran the experiment with one probe sitting outside of the case and one probe inside the case. The ambient room temperature was 74 at the beginning of the experiment and rose to 75 at twenty-two minutes in. It varied between 74 and 75 degrees until thirty-two minutes in and then remained at 75 for the duration of the experiment.

 

The internal case temperature also started at 74 degrees but quickly rose 10 degrees to 84 degrees in twelve minutes after the machine was switched on and began running a BASIC program that finds prime numbers. It rose more slowly an additional 10 degrees to 94 degrees at fifty-four minutes in to the experiment.

 

The internal case temperature was at 94 degrees at sixty minutes in when I turned on a small USB-powered fan I have installed in the case. The temperature began to immediately drop and was at 91 degrees in five minutes. At eighty-four minutes in — twenty-four minutes after turning on the fan — the internal temperature had dropped to 88 degrees where it remained steady until one-hundred and twenty minutes in at the end of the experiment. Over all, the fan created a 6 degree drop in the internal case temperature. The fan is located at the rear of the motherboard and faces upwards to blow towards the native vent slots in the rear part of the top cover.

 

Pictured (Atari 600XL; RF - Channel 3; Hitachi Ultravision) is the table showing the fifteen minutes between 60 and 74 minutes when I switch in the fan and the temperature begins to drop. Also pictured (Atari 600XL; RF - Channel 3; Hitachi Ultravision) is the chart showing the full time/temperature graph. The 3rd picture is the Commodore 64 (S-Video; Hitachi Ultravision) finding prime number 3041 in two hours running Commodore BASIC.

[Willsy]

Try the experiment again with the C64 just sitting at the Ready prompt. I think you'll get the same results. Old CPUs like the 6502 are always running flat out, even if they're "not doing anything".