How to overclock your Sun UltraSPARC box.

Right off the bat, I’m going to tell you that following the tips in this tutorial is probably a bad idea. For the love of everything that is sacred, read the disclaimer page.

It’s important to note that raising the clock speed of any machine (not just Sun machines) generally raises it’s heat output, so you should only try this on a properly cooled machine stored in an air-conditioned room.

I have an Ultra 30 running a 300MHz CPU. I have only been able to get it running at 370MHz before it crashes on me.

In the following example, I am setting the clock speed to 350MHz. Adjust as necessary.
NOTE: Only raise the clock speed a reasonable amount (about 20%) … If you try to run a 300MHz at 450MHz, it will give you garbage on the screen and crash.

The first thing you need to know is what speed CPUs you are currently running. To do that, we need to use the banner command, as listed in our handy-dandy OBP Reference Guide.

	ok banner

When the banner is displayed, take note of the clock speed of the CPU. In the following example, you can see that the CPU is running at 296MHz, (which is what the 300MHz CPUs run at)

	OpenBoot 3.27, 640 MB memory installed, Serial #9428887.
	Ethernet address 8:0:20:8f:df:97, Host ID: 808fdf97.
	Sun Ultra 30 UPA/PCI (UltraSPARC-II 296MHz), No Keyboard

Now let’s get down to some overclocking fun. We’re going to try to get this CPU to run at 350MHz. Type:

	ok also hidden
	ok d# 350 at-speed
	ok banner

Banner information is displayed again. Note the increase in clock speed.

	Sun Ultra 30 UPA/PCI (UltraSPARC-II 344MHz), No Keyboard
	OpenBoot 3.27, 640 MB memory installed, Serial #9428887.
	Ethernet address 8:0:20:8f:df:97, Host ID: 808fdf97.

Ideally, this is only a proof of concept and you shouldn’t really be running your Sun box at clock speeds that it wasn’t designed for.

PS. Don’t forget to drop by for affordable machines for your development environment where you CAN safely experiment with tutorials such as this one.


This solution is UNFINISHED. Here are a few more things I need to test/document before it can be listed as COMPLETE:

  • does clock speed reset to normal after reset-all? if so, can you put these commands in nvramrc?
  • clock speed does NOT reset after a set-defaults.
  • if machine crashes from setting clock speed too high, you can reset to default by STOP+N on keyboard. (is this true?)
  • how to increase clock speed, half MHz at a time by using the “+cpu-speed” command

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