Overclocking / Underclocking...

[Foxdie]

Okay I am creating this thread to alleviate the heated discussions of overclocking the Cxx0 series of Zaurus from other area\'s of the Zaurus User Group.

This is how I have come to understand things as an overclocker of various computer equipment. For the last 3 years I have owned a AMD Athlon 1GHz PC which has been overclocked to 1.3GHz with no problems. The CPU stays under 45\'C / 115\'F (a CPU is considered to be overheating at 65\'C / 150\'F or above) no matter how hard it gets pushed, on these grounds I consider myself quite knowledgible about overclocking devices.

When you overclock something you have to take 3 factors into consideration. Stock (original) CPU speed, what cooling the CPU has and how much the CPU is going to be used at any given time.

The Zaurus doesn\'t have much in the way of cooling, however because the XSCALE CPU is designed for low voltage and it doesn\'t have a FPU it also means that it\'s not going to generate as much heat. Overclocking can void your warranty (but only if you tell the retailer you overclocked it ) and can damage your CPU IF you push it too far.

Within the latest Cacko ROM you have 5 fixed overclocking options which are safe to use on any Cxx0 Zaurus, provided you follow the guidelines later in this post. First of all I would like to take you all through what CPU clock speeds the overclocking utility permits you to set.

[img]http://foxdie.timduru.org/zaurus/cacko/cacko-rom-overclock-settings.gif\" border=\"0\" class=\"linked-image\" /]

As you can see, when you overclock or underclock the Zaurus you are also changing the values of the RAM (not the storage media) and the bus speeds (the speed at which the CPU communicates with other devices). No matter what value you choose there should be no corruption of data (although if this has happened please correct me, I haven\'t heard a report of it yet!).

People who should consider overclocking:

People who run emulators eg. gnuboy


• People who want to use their Zaurus for Video
• People who need to calculate data faster, for example WEP cracking
• People who think the Zaurus is running too slow

People who don\'t need to overclock:

People who use PIM\'s eg. Calendar App


• People who use their Zaurus for MP3\'s
• People who surf the net and/or use WiFi
• People who use communications Apps like QPE-GAIM

People who should consider underclocking:

People who use e-book readers


• People who are checking email automatically
• People who generally want to display the same screen / image without it changing
• People who want to get more battery life out of their Zaurus

Overclocking with the tray applet in the latest Cacko Qtopia ROM is safe. It doesn\'t push the CPU speed too far and there is a minimal heat increase. If you\'re still a little wary of overclocking but feel it may help you here is a guide based on model:

C700: You can run it at the Overclock level but only for short periods of time (no more than 15 minutes), it pushes the memory clock quite high in relation to it\'s stock speed. The default for the C700 is \"Default (PXA250)\".

C750, C760 and C860: You can run it at the Overclocked level for as long as you desire but don\'t use it for more than an hour if you wish to keep your Zaurus in top condition. The default for this series is \"Default (PXA255)\".

Remember, when you\'re charging your Zaurus battery, extra heat is generated, due to this you should cut the above overclock time in half if you have your Zaurus connected to it\'s charger.

Cool down time for all Zaurus is 30 minutes. After 30 minutes has gone you can safely overclock again. Be warned though that repeated overclocking / underclocking can cause heat expansion which can physically damage your Zaurus.

Other ROM\'s have the ability to set the clock speeds differently, you can set the CPU as high as you want with it. As such this is very dangerous. You should NEVER overclock your Zaurus more than to 471 MHz (the next step up is 530 MHz which is too far). Use the table above as a guideline for the maximum safe overclocking speeds!

Please feel free to ask any questions, and also before you post PLEASE use your common sense when typing your posts. Any post that is deemed by myself or the other ZUG team as inappropriate or in any way offensive it will be deleted.

[Anonymous]

Ok...I\'ll bite.  Excellent post.  Very well thought out and presented.  But again...issue with the word \"safe\".  You said \"Overclocking with the tray applet in the latest Cacko Qtopia ROM is safe.\"  But then you go into some guidelines on how to make over-clocking not do too much damage over the long haul.  I would recommend you change the \"Overclocking with the tray applet in the latest Cacko Qtopia ROM is safe\" to \"Although Overclocking can be risky and void your warrantee, here are some guidelines that will help lengthen the life of your Z when over clocking and minimize its effects, if any.\"

Its just a recommendation.

[realistic_dragon]

Presumably installing this ROM on any device will leave it in a normal clock state by default unless you change it?

[offroadgeek]

If you ask me, this is just a matter of symantics.  Take bungie jumping for example... if someone tells you that bungie jumping is safe, and you should try it, would you not first do some research to better understand what you are getting into prior to taking your first jump?

the same should apply with overclocking...  if you are thinking about overclocking your Z, do some research of your own (more a suggestion to others, because if you are the same \"guest\" that is in the other thread, you have clearly shown that you\'ve done your own research on the topic), then make an educated decision as to whether you will use this feature or not.

That said, I agree with you in warning people about using the word \"safe\" with overclocking.  Especially if you are a company selling a product and could possibly face legal issues by possibly misstating the capabilities of the product.  However, foxdie and maslovsky are simply individuals with educated opinions, and neither of them are providing any guarantees that overclocking won\'t damage your processor or any other components.

Lastly, there are some fundamental consumer responsibilities when purchasing a product, such as understanding the warranty.  If a consumer doesn\'t fully understand their warranty, and what could void the warranty before doing something like overclocking, then it\'s their ignorance that is to blame, not a post on a zaurus forum.

[Foxdie]

Presumably installing this ROM on any device will leave it in a normal clock state by default unless you change it?

To my knowledge no ROM is supplied with overclocking enabled by default, if it is the ROM developer is a fool. Not many people want or need to overclock their Zaurus.

The Cacko Qtopia ROM is no exception, the ROM is definately supplied with the CPU set to run at default speed. Even when you reboot the CPU is set to run at default speed as a precaution.

You can check what speed your CPU is genuinely running at by going to the CPU (third) tab on System Info on the latest Cacko Qtopia ROM, or you can click on the little traffic light icon by the clock to select a CPU speed option.

[Randy_003]

umm. just curious Foxdie, how slow does Gnuboy run on your C760?

[Foxdie]

Admittedly there\'s a problem. I can\'t seem to start any games due to key bindings, there\'s no middle button on the C series (to start games, the joypad style control on the 5x00 series).

Running at default speed it runs slightly slowly, the sound has micro-skips. If I run it at the overclock level it seems to run at 100% emulation speed.

[raybert]

Foxdie, have you tried the space bar?  The middle button on the 5x00\'s mapped to the space key.  I\'ve found that most apps that used the middle button on the 5x00\'s respond to the space bar on the c-series.  It\'s a little akward to use though for some apps.

~ray

[ScottYelich]

I\'d remove the words \"safe\" .. just for legal / liability reasons. :-]  I mean, people *are* crazy
(What? you mean this gun could actually HURT me?  I thought you said it was safe!!!!)

Also, are you sure about the overclocking the 700 pushing it too much?  I thought it was
also 397mhz... default... just had cache disabled?  pxa250 = 397, cache disabled
pxa255 = 397, cache enabled?

seems 471 is the same jump for both, if that above 397MHz is true ( for both)

Scott

[CoreyC]

Nice debate going on here

I have not yet felt the need to overclock my c760, but I did play around with it a little with my sl5600 when using emulators and some multi-tasking like listening to shoutcast streams and browsing with opera at the same time.  My c760 can do this w/o any problems while the sl5600 had some trouble... (Overclocking didn\'t help BTW)

On my sl5600 you can feel the heat difference while overclocking, and I noticed only a minimal change in preformance.  I wouldn\'t recommend overclocking the 5600 at all.

[Stubear]

Overclocking can void your warranty (but only if you tell the retailer you overclocked it ) and can damage your CPU IF you push it too far.

You don\'t need to tell them. Overclocking for any reasonalbe length of time causes changes to the cpu that are noticable. Not sure what the changes are, but I used to do proof-reading for a tech at Toshiba in Japan and was asked once to proof-read a letter telling someone that they wouldn\'t honor the warranty on their laptop cause it had been overclocked - Toshiba stated that this had caused the problems and they weren\'t gonna fix it.

Stu

[maslovsky]

Overclocking for any reasonalbe length of time causes changes to the cpu that are noticable

Sorry, but this is nonsence.

[Foxdie]

Overclocking for any reasonalbe length of time causes changes to the cpu that are noticable

Sorry, but this is nonsence.

Actually what Stubear said is true, but only if you overclock too far.  Overclocking an Xscale CPU greater than 471 MHz will cause it to overheat and PERHAPS warp the CPU packaging. The next stage of overclock from 471 MHz is 530 MHz which will void any warranty.

There is also the argument that you can\'t tell an overclocked CPU from a badly cooled normal CPU. I think that the heat expansion will cause micro-fractures in the CPU casing that can be examined under a microscope. Manufacturers should have taken this into consideration.

These are all extreme suggestions though

[Stubear]

Overclocking for any reasonalbe length of time causes changes to the cpu that are noticable

Sorry, but this is nonsence.

Can you prove this? I\'m just stating what I was asked to proof-read. I\'ve seen several laptops where oveclocked cpus melted holes in the case. Are you telling me that you are 100% positive that the increases heat caused by overclocking leaves absolutely no traces?

Stu

[lardman]

There must come a point where the extra heat does do damage, it\'s just trying to work out what that point is. I image there are some overclocked speeds which will never do any damage (the heat dissipation into the atmosphere/rest of the Z is sufficient to stop it), and some which will eventually (or even very quickly).


Si

P.S. I spell-checked \"dissipation\" in MS Word to check I\'d spelled it correctly and the thesaurus gave me the following as alternatives: debauchery, indulgence, rakishness. Is this some strange Americanisation or did I get the wrong word ;-)?