"Yes" forces one core into an endless loop writing garbage to a null output. It's a great way of loading one core to 100%. You can open 2x terminal windows and get both cores to 100% if you want, that way the CPU consumes its full 25 Watts.
Actually I think your Mac is OK. I've got an old 2006 MB and just played with it and saw much the same thing as you:-
idle, fan 1500 CPU around 60 C
1 core loaded (1 x "yes" command) CPU at 80 C, heatsinks at about 64, delta-T = 80-64 = 16 C, consistent with 12-15 W coming out of CPU. Fan at 6000 rpm (yes, 6000 rpm)
2 cores loaded (2 x "yes" commands) CPU at 86 C, heatsinks at about 65 C, delta-T = 86 - 65 = 21 C, consistent with 25 W coming out of CPU. Fan at 6188 rpm
Basically my 2006 MB ramps its fans up to 6000+ rpm at the slightest provocation, even 1/2 CPU load.
So I think I was wrong, you don't have a blocked air path, it's just that the cooling system on the old pre-unibody MBs wasn't that well designed, the fan has to work really hard.
Get a flash blocker! Sorry to waste your time with all the "yes" stuff!
(I've got a unibody MBP now, the fans rarely wind up even under full load. I guess I've got used to it. Thinking back my old MB used to be quite annoying when watching Flash)
Sorry again.
Pax
Actually I think your Mac is OK. I've got an old 2006 MB and just played with it and saw much the same thing as you:-
idle, fan 1500 CPU around 60 C
1 core loaded (1 x "yes" command) CPU at 80 C, heatsinks at about 64, delta-T = 80-64 = 16 C, consistent with 12-15 W coming out of CPU. Fan at 6000 rpm (yes, 6000 rpm)
2 cores loaded (2 x "yes" commands) CPU at 86 C, heatsinks at about 65 C, delta-T = 86 - 65 = 21 C, consistent with 25 W coming out of CPU. Fan at 6188 rpm
Basically my 2006 MB ramps its fans up to 6000+ rpm at the slightest provocation, even 1/2 CPU load.
So I think I was wrong, you don't have a blocked air path, it's just that the cooling system on the old pre-unibody MBs wasn't that well designed, the fan has to work really hard.
Get a flash blocker! Sorry to waste your time with all the "yes" stuff!
(I've got a unibody MBP now, the fans rarely wind up even under full load. I guess I've got used to it. Thinking back my old MB used to be quite annoying when watching Flash)
Sorry again.
Pax