How hot is too hot?

How hot is too hot for a Tbred A 1800+?? I'm running 38 degrees at a Vcore of 1.8

anything under 60 is tolerable in my book.. i keep all my rigs under 45 though. That of course is full load after at least .5 hour @ 100 percent load. If you can stay under 40* then that is fantastic

I wouldn't be comfortable sitting above 50 degrees celcius at system idle. Actually, I would be more comfortable with a temp of ~45 degrees.
Basically once your temps start to increase, the performance factor of overclocking starts to decrease...you just have to find the right balance.

I get uncomfortable above 45, and 50 is the highest I would let my temps rise before powering down.

Of course, I don't worry about that anymore, since I haven't been above 40 in months, and rarely go above 35.