[geeks] Any Ultra 20 owners out there?

[Charles Shannon Hendrix]

Tue, 13 Feb 2007 @ 13:26 -0600, Lionel Peterson said:

> Hello all,


> Also, before I upgraded the BIOS/CPU, I tinkered with the CPU Freq.,
> going from 200 MHz to 205 MHz, but the ability to tweak the BIOS Freq.
> speed is not in the latest BIOS, so my CPU is running at an eye-poping
> 1.85 GHz ;^) I am considering taking the BIOS back to an earlier
> Revision, in hopes of finding the speed adjustment - I would like to
> take this up to 2.2 GHz. The BIOS used to offer a +50 MHz adjustment,
> and I'm hoping I can find that option again...

You might already know all of this, but I thought I'd relate my
experiences with Opterons and clock distribution.

When you overclock a CPU with a low multiplier like the 165, you have to
push the system harder than with a 170 or higher. The CPU doesn't matte
since Opterons are not binned parts, but the rest of the system is more
senstive.

I don't know the details of the U20 clock distribution, but it might not
have separate lockable multipliers like a lot of PCs, and that could be
why they removed clock options in their BIOS. That's what happened with
the K8T chipset boards: their clock distribution never fully worked, so
they removed the options in later BIOS revisions.

For example, if you want to get 2.4GHz CPU speed with a 9x multiplier,
your multipliers and final speeds will be:

	CPU: 266 * 9 = 2400MHz
	HT: 266 * 5 = 1330Mhz
	RAM: 266 * 2 = DDR533

The CPU will be OK.  HyperTransport 1.0 comes in 800MHz and 1GHz
flavors.  800 most certainly won't be reliable at 1.3GHz, but 1GHz HT
might.  You won't get much benefit from doing it in any case.  I'm
pretty sure the Sun U20 is 1GHz HyperTransport (DDR2000).

RAM: it probably will not run at 533MHz reliably, if at all.  Doesn't
the Sun U20 use DDR400 RAM by default?

If the U20 cannot lock multipliers variably and independently, you would
have to set your base clock to whatever speed the slowest component
could tolerate. Suppose Sun's RAM can run at 410MHz maximum and it is
the slowest component. That means your best overclock would be:

	CPU: 205 * 9 = 1845MHz
	HT: 205 * 5 = 1025MHz
	RAM: 205 * 2 = DDR405

Not much of an overclock, which is why the Opteron 165 is a bad choice
if your motherboard doesn't have a flexible clock system.

If the U20 *does* have independent multipliers, then you could do this:

	CPU: 266 * 9 = 2400MHz
	HT: 266 * 4 = 1064Mhz (very close to stock)
	RAM: 266 * 1.5 = DDR399 (very close to stock)

Nice CPU boost, but otherwise leaves the motherboard at stock speeds.

Here's my own system timing:

	CPU: 250 * 10 = 2500MHz 
	HT: 250 * 4 = 1GHz (stock speed)
	RAM: 250 * 1.6 = 408MHz (close to stock speed)

I also locked my PCI and PCIe busses to stock speed, since this
motherboard has the option of using either the system clock, or
independent clocks for those busses.

I would be very interested in what kind of clock system the U20 has, so
please let us know if you find out.

> I used the cooling solution that came with the new CPU, it has 4 pipes
> where the original piece had two, so I decided it was "better", though
> it otherwise looks smaller...

The Opteron heatsink is nice one with heat pipes and a very good fan.
It's better than most aftermarket coolers and was designed for 24/7
server usage.




-- 
shannon           | It's a damn poor mind that can only think of one way 
                  | to spell a word.
                  |         -- Andrew Jackson