OLPC XO Hacks: Overclocking an XO Laptop Geode LX 700 CPU

   
   
   
   
   
xo laptop overclocking
Waves of XO speed

One major complaint about One Laptop Per Child's XO laptop, is the speed of its Geode LX 700 CPU that runs at 433mhz. Most experienced computer users find it a little slow, and often compare it to computing in the late 90's.

On the other hand, OLPC's target market, children in the developing world who don't have a Dell or Xbox for comparison, don't seem to mind.

Still, for the serious geek, there is an easy fix for a slow processor: overclocking. That is making the processor run faster than it's designed to do. Now, thanks to bdleonard on OLPC News XO Hacks Forum, we have directions on how to overclock your XO laptop:

Overclocking of the Geode LX processor is easily accomplished by writing to a specific MSR (Model Specific Register). This is easily accomplished at the open firmware prompt. To get to the open firmware prompt you press (the X in the upper left hand corner of the keyboard) immediately after booting the OLPC.
  1. Type "4c000014" and press
  2. Type "rdmsr" and press
  3. Type "u." and press (a hex number will be displayed)
  4. Again, type "u." and press (a second hex number will be displayed, write it down)
  5. Now its time to overclock.
For this to work, you must have a developer key, or have previously disabled security on your OLPC.
Now before you get crazy, overclocking a CPU isn't without risk - it may cause stability problems, data errors, and possibly hardware damage, and will generate excessive heat, a concern with the passively cooled XO laptop. Overclock at your own risk.

xo laptop overclocking
XO CPU drag racing

Regardless of your bravery, check out the results achieved by GoremanX:

I did some informal testing to see what speed improvements I get with overclocking. I've been able to run reliably at 566/233 (6e1) under Ubuntu from an SD card.

For the record. 566mhz is a 30% improvement in processor speed over the stock 433mhz, and 233mhz is a 40% improvement in memory speed over 166mhz.

On average, I saw a 21.8% improvement in usable system speed at these overclocked ratings. In my opinion, Ubuntu ran much more smoothly and responsively at 566/233. I did not notice if battery life was noticeably affected.

With usage speeds jumping like that, soon we'll have Geode LX 700 drag racing!

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12 Comments

"The OLPC XO gets overclocked, loses its innocence"

And here I thought they lost their innocence when the kids started using them to look at porn.

When do the benefits of overclocking the XO CPU overcome the disadvantages?

There mostly is a reason CPUs are sold at a specific clock frequency.

However, the reason can be market segmentation, ie, ripping off customers.

Winter

A 22% improvement in application speeds is a definite advantage to overclocking the XO. The main disadvantage would be heat generation. I would not suggest overclocking in Mali or Sudan, but in Peru, at higher elevations where its cold and wet, the speed does make a difference.

I look forward to doing this to my own XO ... after a few brave early adopters do it for a few months without hardware problems...

No, the cpu and ram is important.

There are many applications were left out just because there is not enough power.

A little sanity here, please?

Personally, I'd rather not push the envelope on the chipset. (I'm an ex-hardware designer: clock rates are what they are because the engineers can't be sure the chips will work properly at much higher speeds.) 20% speed improvement while executing a word processor isn't going to make your day. But getting the wrong answer for your checkbook could spoil it.

Overclocking is a neat hack and it's cool to be able to claim you did it. But given how hard it is at present to obtain replacement parts for your XO, are you willing to risk frying the CPU? Do you even have the skill and tools to replace the chip if you cook it?

So any day now I should expect to see a youtube video of an overclocked XO bursting into flames and exploding.

@davewa
Thanks for the note of caution. As fun as this sounds, I don't want to try it before widespread testing. I'm pretty sure the OLPC engineers already thought of this and ran into problems, otherwise they'd have shipped it overclocked. I don't want to brick my XO-1 even if I had a spare.

All that said, I bet the sweet spot turns out to be at whole or half ratios like 500/166 (3.0), 500/200 (2.5) or 466/133 (3.5) based on my experiences with the early days of PC overclocking. In fact, 500/166 seems best to me as it preserves often sensitive memory timings while yielding ~15% improved performance.

@eduardo
Actually, the XO-1's fancy LiFePO4 batteries DON'T explode and burst into flames. That's the entire point. They are extremely safe and stable, unless you heat them to over 800 degrees Celsius. LiFePO4 is one of the few battery chemistries almost safe enough to just toss in the trash can. I read the only downside is they don't output quite as much power as other battery chemistries.

An overclocked or overheated XO that goes south should just quietly crap out. Period. Google "Lithium Iron Phosphate battery" for more info.

How does this affect battery power consumption and running times? Not the lifetime of the battery itself - I'm not worried about it exploding - just how long you can run it without recharging. My guess is that the components aren't too fragile, and the official 6-hour run time is enough better than my typical work laptop that unless I'm using it on an airplane it'll be just fine, but with third-world electricity or crank or solar power, it's better off not overclocking.

I have been trying to get to the open-firmware prompt to disable security & try this overclocking trick for a while, and I am uncertain as to the timing of pressing the esc key... Seems if I press it to send a single character, nothing happens, and if I hold it down from initial power-on through the first display of the gui, this ascii display comes up, but goes away after a few seconds regardless of what I type or don't.. even if I hurry & type 'disable-security', it just goes to sugar right away. What's even odder, I got two - one for each of my kids, and they both do the same thing.

Any help appreciated.

Thanks for the note of caution. As fun as this sounds, I don't want to try it before widespread testing. I'm pretty sure the OLPC engineers already thought of this and ran into problems, otherwise they'd have shipped it overclocked.

they could have kept the clock speed down to prevent theft that's why they use sugar instead of something else

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