Rodney Fletcher’s Blog

If you’re a fan of cheap / fast / powerful hardware, then you’ve played with dual core AMDs more than a few times by now. If you’re a fan of Linux, then you may well have hit a snag, here.

You see, there’s a problem in the way the kernel addresses interrupts on the AMD dual core processors and the net upshot is, you can’t do it (out of the box). Rest assured, however, you can do it with a little work. Anyway, it’s Linux – of course there’s some more work involved! (At least it won’t kick you out of your own computer, though).

The situation you may find yourself in is this. You have a fresh new machine ready to go and you begin the Linux install process. This runs smoothly, probably fast as hell, too, on your shiny new box. After completion, the computer reboots, says “Decompressing the kernel” … and that’s it. It just sits there doing nothing. It’s hung.

The problem is, the installer runs in single processor mode but is smart enough to see you have two processors. So it installed the SMP kernel and set it as the default. Now you find you can’t boot up the new install, unless you interrupt the boot process and select Single CPU mode. Then it works, but you’re only useing one core.

The Solution:
To fix this problem, you’re going to need very little know-how and it won’t take too long. All you need to do is reconfigure the kernel to run in “noapic” mode. This can be done as follows:

1. Boot up in single processor mode, i.e. don’t pick the SMP kernel.
2. Locate your boot loader config file. I will assume you’re using GRUB and that the location of the config file is /boot/grub/
3. Edit grub.conf and ensure that noapic is added to every SMP kernel line.

As an example:
title CentOS (2.6.9-55.0.2.ELsmp)
root (hd1,0)
kernel /vmlinuz-2.6.9-55.0.2.ELsmp ro root=/dev/md0 noapic rhgb quiet
initrd /initrd-2.6.9-55.0.2.ELsmp.img

That’s it! You should find you can now boot your system in SMP mode.

So what’s different?
Valid question. What have you lost by using noapic mode? In short, this means your CPU(s) will have to acknowledge all interrupts, which will slow you down a little. Will this be a big issue? Probably not. If it is for you, well you have two choices:

1. Don’t use noapic and stick to one CPU. Obviously, you’re not going to do this because if you wanted one CPU you wouldn’t have bought a dual core.
2. Go buy an Intel based processor. Obviously you’re not going to do this because if you wanted an Intel chip, you’d have bought it in the first place. Plus you’d need a new motherboard to go with it. And it would be 32bit, not 64.

So in short, this is what you have to do. If it’s not 100% best performance possible, bad luck, coz your alternative is even worse.

Hopefully it will just be something future kernel releases don’t suffer from or future AMD chips don’t suffer from.

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Recently, I have had a lot of problems with Microsoft Vista. Suffice to say I have nearly chucked it in the bin in more than one instance.

The root of these problems has been Vista’s psychotic anti-piracy controls, being:

• Validation, &
• Activation

The Windows Genuine Advantage system. Lately, I’ve been seeing very little of the advantage.

It all started when I changed my video card. I’m not going to go into details, as I already have in the link above. After this change, however, I was told that my system was no longer genuine and required a new activation code. This involved a call to a support centre, with a very long wait but did, in fact work.

…for a time…

Then came the validation issues. Some short time after Re-activation (due to changing a video card), my system kicked off a routine Windows Update (all by itself), which required Validation. Validation requires Activation. This is where I got messages telling me my system couldn’t be Validated, as it was not Activated. However, it was Activated. I’ve attached a screenshot below, to show the stupidity of the situation.

To cut a very long story short, I had to format to clear the problem. As I fully suspected, however, it just reoccured a few days later. You see, my license key is now listed at Microsoft as being already used. So this problem is here for life.

So now I get the odd re-Activation message, when I am sitting here doing nothing important, certainly not installing new software or hardware. I’ve learned the code they give you over the phone almost by heart (it never changes, so I don’t really see the point of it).

For me, the shine has really rubbed off, from Vista. Read the link above to get the full picture.

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I have gone for allowing Captcha on this site, now. Until recently, all comments were moderated (ignored), so the site became too stale.

With this change implemented, please feel free to comment to your heart’s content.

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