Overclocked LC520

[just.in.time]

I overclocked my LC520 from 25mhz to 33mhz following the instructions here: https://www.thinkclassic.org/viewtopic.php?id=600

I forgot to feel how warm the CPU gets prior to overclocking it.  However, after overclocking I ran some games for a bit with the rear cover door off.  When I feel the CPU it is definitely warm-hot.  I can touch it without burning my finger, but only barely.  Is that standard for a 33mhz 68030?

I'm guessing it is probably fine.  My only concern is that I have the PDS slot ethernet card in place, and while it isn't directly touching the CPU, there is definitely no room for a heat sink... and even if there was, it would basically be transferring that heat directly to the ethernet card.

Can anyone give any opinions or input?

All that said, it ran fantastic for the 30 minutes or so I ran it  Nothing out of the ordinary, and the floppy drive seems to still read and write as it should.  I didn't test the serial ports since I have largely moved most of my machines to ethernet or they have access to a SCSI Zip drive, so I haven't busted out the PhoneNet adapters in a while.  Does the 68030 have a thermal shutoff to save its self from overheating damage?

 

[rsolberg]

Microprocessor thermal protection was pretty much unheard of before the early '00s. In x86 land, later Pentium III CPUs would shut down the system, Pentium 4s would reduce their clock speed, and Athlon XPs would release the magic smoke. https://youtu.be/BSGcnRanYMM

The LC520's logic board and CPU are probably just underclocked anyway. By the time these arrived, my guess would be that any 68030 Motorola shipped rated at 20 or 25MHz was capable of 33MHz within specs.

The 33MHz 68030 has power consumption under two watts and would have to hit 90C internally to exceed its thermal junction rating. Based on a 15C thermal resistance of the CQFP package, a maximum surface temperature under 75C would be theoretically okay. 65C or below would be safe. 43C is about the hottest surface most people can tolerate for a few seconds. At 48C, you'll have first degree burns in a blink. TLDR: If you're not burned, it's okay.

 

[just.in.time]

Rsolberg, thanks for the reply. I was definitely able to hold my finger on it for several seconds. While uncomfortable, definitely no burns okay, I'm not going to worry about it then.

 

[olePigeon]

If you're really worried, you can always attach a heatsink & fan.

 

[just.in.time]

My worry will have to take a back seat. The Ethernet card on the PDS slot covers the CPU. Not enough clearance to squeeze a heatsink on.