Overclocking!!!!!!!... ?

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ChedderCheeser

Senior Member
Hey guys, just a quick question... I know that an 08M is capable of 8MHz, but is it possible to overclock it higher than that? Because.. its not much of an overclock if its MADE to be sped up.. like.. my P4 CPU isnt really.. MADE to be overclocked, but I did... You know what I mean by that? Hope so. :D
 
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srnet

Senior Member
In theory for devices that can be fitted with an external reasonator, you could.

But the 08M is not designed for an external resonator.
 
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BillyGreen1973

Senior Member
As srnet stated, in theory yes. However you have to remember, if you use an external crystal or resonator that is outside the stated range, then you will probably see undesirable things happening. For example, the serial in/out of the picaxe may not function properly, the timers/servo commands will probably be messed up, and even simple things like 'wait' and 'pause' commands may even fall down.
Bottom line is, why bother? if you need a fast Picaxe use one that can do it, e.g. 28x2 or 40x2 can do 64Mhz with a 16Mhz resonator.
 
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vttom

Senior Member
Funny you should ask. I looked into overclocking an 08M some time ago. I never got around to doing it, but I think it is possible.

If you look in PICAXE Manual 1, you'll see that the 08M corresponds to the Microchip part PIC12F683. If you go to microchip.com and plug in that part number, you can make your way to the data sheet for that part. Here's a direct link -> http://ww1.microchip.com/downloads/en/DeviceDoc/41211D_.pdf

If you dig around in there, you'll find that this part does, in fact, accept an external oscillator, spec'd up to 20MHz, which is 5x the nominal 4MHz. You could probably stretch it beyond that if you wanted to once you got it working with an external clock source.

What I don't know is if you are able to poke the various config registers at runtime in order to switch-over the 08M into external oscillator mode. If not, you might need to do some hacking where you put the part in the native PIC serial programming mode (called ICSP my Microchip) and go at it that way.
 
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jtcurneal

Senior Member
I would suspect that if you did were able to poke the various config registers to use an external resonator that you would never be able to download another Picaxe program in that chip. The 12F683 uses leg 2 and 3 for the external resonator, and a Picaxe o8M uses leg 2 for downloads.

Joel
 
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nick12ab

Senior Member
jtcurneal said:
I would suspect that if you did were able to poke the various config registers to use an external resonator that you would never be able to download another Picaxe program in that chip. The 12F683 uses leg 2 and 3 for the external resonator, and a Picaxe o8M uses leg 2 for downloads.
Click to expand...
The SFRs aren't stored in EEPROM and not applied until your program starts if the program sets them so the serial in pin isn't a resonator pin until after the bootstrap has checked for a download first.
 
hippy

hippy

Ex-Staff (retired)
All PICAXE have 'hardware configuration fuses' which can only be set during production line programming. Some of these fuses determine if a primary external oscillator can be connected or not. For those PICAXE which don't allow connection of an external oscillator it won't be possible to add or use one under program control.

The 08M can only use an internal oscillator, and is 8MHz maximum.

From my experience, trying to alter the fuse settings of a PICAXE will, at best, get you an empty PICmicro, at worst, something to throw in the landfill.
 
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Dippy

Moderator
Absolutley. If you don't know what you are doing then spend the extra pennies on a device designed (for you) to do the job you want.
I accidentally overclocked a dsPIC once and it turned into a George Foreman grille ... except smaller.:eek:
 
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srnet

Senior Member
I mean, maybe you could make turn an AF117 into a microwave transmitter or a (black painted) 0C71 into a receiver for a laser fibre.

But as the sub guru says in Hunt For Red October "why would you want to"
 
hippy

hippy

Ex-Staff (retired)
ChedderCheeser said:
http://www.youtube.com/watch?v=-U-cc_Qcf-w
Thats what inspired me. I know its a******, but still. I wanted to O.C. the 08M since i will soon be buying a 40X2 and a 18M2 so.. yea. Anyway, Thx!
Click to expand...
"Over-clocked, liquid-cooled, running at 32MHz" ... I think the liquid cooling might just be a tad overkill. If it had burst into flames, spat sparks and smoked when removed from the liquid, that may have justified it and would even have been impressive. I can't however see the justification for liquid cooling or I'm missing something.

In the PICAXE universe there are two variants of over-clocking. First, taking it above its default 4MHz or 8MHz speed, and the 20X2 zings along at 64MHz without needing oven gloves to touch it. Then there's the 'hardcore over-clocking' in the traditional sense which means running it faster than Microchip say it should be. For over-clocking like that the 28X2 and 40X2 are your only options.

As noted in the link earlier, I got a 28X2 up to 100MHz, no fancy cooling, no noticeable temperature increase.
 
premelec

premelec

Senior Member
Long time ago...

About 50 years I tried to get a planar silicon transistor to dissipate much more power by grinding the cap open so I could immerse the unit in FREON [B.P. 80DegF] - it boiled the liquid nicely and shorted out at only slightly higher power than 'usual' however before it died there was a purple pink light coming out around the chip pattern - an early LED of a color I had never seen come from a solid state device... [I was watching with a microscope]. You never know what you'll find when you try something strange... have fun...
 
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Haku

Senior Member
premelec said:
You never know what you'll find when you try something strange... have fun...
Click to expand...
Whilst not in the same league as slicing the tops off early transistors, I discovered laser light will stop glowing things from glowing...!

Years ago when I got a laser pointer before they became commonplace & common knowledge they were available (it was £35 from Tandy and used N sized batteries), one of the things I tried was trying to 'write' on a sheet of glow stars with the laser light, only to find that the laser light made the charged phosphor material go dark.

Both red and green laser light causes black dots/lines on charged glow things, I don't have a blue laser to test with though.
 
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Paix

Senior Member
I think that the liquid coolant should be reserved for the grown ups after a hot programming job, or before and during.

Ice cold in Alex' maybe.
 
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John West

Senior Member
I figure if I can't do the job with a stock-clocked many-legged 64 MHz PICAXE, (and a few slave 08M's) it's probable too demanding a task for me to do anyway....

In fact, any job that even needs the above is probably too demanding for me. I'm still trying to figure out how to read a handful of Dallas DS1775 chips. When I reach a point where I feel the need to overclock chips, I'll holler. It'll be awhile. My learning curve is pretty flat these days.
 
premelec

premelec

Senior Member
@Haku - very interesting - with a red laser here I noticed that it seems to have more effect when a few feet from the glow plastic - and notice the glow recovered when re-charged with photons... effect must be good for something :)

@John - hope your beer ain't as flat as your learning curve - my learning curve has turned to a negative slope - the joys of aging brain!
 
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nbw

Senior Member
premelec said:
About 50 years I tried to get a planar silicon transistor to dissipate much more power by grinding the cap open so I could immerse the unit in FREON [B.P. 80DegF] - it boiled the liquid nicely and shorted out at only slightly higher power than 'usual' however before it died there was a purple pink light coming out around the chip pattern - an early LED of a color I had never seen come from a solid state device... [I was watching with a microscope]. You never know what you'll find when you try something strange... have fun...
Click to expand...
Hey, careful releasing that magic smoke! :)
 
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