The past few days have been a bit of a (mis)adventure in the world of overclocking, in a way. I did not set out to overclock or overvolt anything. I simply assembled the parts I had and hoped or expected to have things just work, or at least mostly work since the hard drive's OS was installed with somewhat different hardware. This almost happened.
If I set things to use only the standard Sempron single core, things worked about as expected. An old PCLinuxOS install came up but needed the invocation of CONTROL-ALT-MINUS a time or three to get viewable video on the (now ancient) CRT monitor and I needed to fiddle with the filesystem permissions a bit. No big deal, the drive will be wiped anyway.
The kicker was that I couldn't even get a memory test (and the memory itself seemed to pass it well enough) more than about 4 and half minutes if I tried to unlock/enable the second core. Following the suggestions on an old overclocking/unlocking forum  I eventually found that I needed to adjust the NorthBridge voltage up a notch to get stability. I then finally noticed it was running the RAM at 1333 MHz rather than 1066 (which is the actual rating of the hardware). I tried switching things from AUTO to 1066 to see if that helped. It didn't. Since I have to run the NB voltage a bit high anyway, I may as well run the memory at 1333 since it can do it. The memory test ran overnight and only stopped because I stopped it.
All this is a bit annoying as the same RAM and CPU worked fine without any odd tweaking on the Gigabyte motherboard. Had I started with this one, I doubt I would have made all the adjustments I did (upping voltages always feels risky to me) and just figured I got one of the (rare?) truly single-good-core Semprons even though I had not.
One thing ASRock does get right, that Gigabyte earns a big fat FAIL for, is having BIOS updates in regular plain ZIP files rather than some silly Windows .EXE thing. ASRock would be more impressive if their US servers worked properly. As it is, I had to go to an Asian or European server to get both the BIOS update(s) and the manual pdf.
An odd thing is that there is no obvious option to boot from USB, yet it supposedly is there. According to ASRock's FAQ one needs to press the right function key (F11) at boot and then select the connected USB device from which to boot. It's not exactly transparent.
I've now run into the next roadblock: An old monitor with limited resolution and frequency, which isn't working with a couple LiveCDs, even when I set the vga option in the boot line. I really don't want to play cable swapping games to something that should be simple. I also don't want to pay a lot for another monitor or a DVI (or HDMI) switch. This should easy, but I suspect *buntu is being "helpful" yet again.
 At least in one way I was ahead of things. I swapped the stock Sempron heat sink and fan for the heat sink and fan that came with the X6. Here, it's overkill and so far doesn't seem to be annoyingly loud.