Actual Mhz And Overclocking?

[thomasmes]

If I look at the specs I see 600+ Mhz. Is it 600 Mhz or 625 Mhz and can it be overclocked like the GP2X?

Is the speed 600 Mhz on battery and more when it's connected to a power supply?

If I look at the CortexA8 specs I see that the CPU is delivered in various speeds: 600Mhz to 1Ghz

Anyone?

 

[mindlord]

If I look at the specs I see 600+ Mhz. Is it 600 Mhz or 625 Mhz and can it be overclocked like the GP2X?

Is the speed 600 Mhz on battery and more when it's connected to a power supply?

If I look at the CortexA8 specs I see that the CPU is delivered in various speeds: 600Mhz to 1Ghz

Anyone?

It is 600mhz by default, but like many (if not all) ARM processors it can be Under/Overclocked dynamically and on the fly. 600 is good because it leads to a nice round 10 hours of battery life under normal usage. You should be able to underclock it down to a crawl and just play mp3's for days without recharging! Or Overclock up to 900mhz and play heavy emulators without any hangs or lockups for a few hours before needing a recharge. More than 900 and stability will decrease.

 

[thomasmes]

If I look at the specs I see 600+ Mhz. Is it 600 Mhz or 625 Mhz and can it be overclocked like the GP2X?

Is the speed 600 Mhz on battery and more when it's connected to a power supply?

If I look at the CortexA8 specs I see that the CPU is delivered in various speeds: 600Mhz to 1Ghz

Anyone?

It is 600mhz by default, but like many (if not all) ARM processors it can be Under/Overclocked dynamically and on the fly. 600 is good because it leads to a nice round 10 hours of battery life under normal usage. You should be able to underclock it down to a crawl and just play mp3's for days without recharging! Or Overclock up to 900mhz and play heavy emulators without any hangs or lockups for a few hours before needing a recharge. More than 900 and stability will decrease.



Wow, I seldom had such a clear answer. As with the GP2X, overclocking can reduce the life of the CPU. Is that the same with the Pandora?

 

[craigix]

It might reduce the life of the CPU but it would still last for many years.

 

[bigtruck]

I would think the only thing you could do that might seriously reduce the life of the CPU would be to set the voltage over the recommended limits (which from what I've read is software controllable).

 

[Squidge]

Wow, I seldom had such a clear answer. As with the GP2X, overclocking can reduce the life of the CPU. Is that the same with the Pandora?

Overclocking doesn't reduce the life of a CPU. Overvolting and overheating does. It can reduce the life of the processor, but even if it was 10 years instead of 25 years; do you really see yourself using a GP2X or Pandora (MK1) in 10 years?

Secondly, the maximum allowed software voltage for the OMAP is still within spec, so it shouldn't reduce it's life at all (unless of course you have a thing about playing the Pandora whilst inside large ovens, in which case, you'll probably cook before the Pandora dies )

 

[anexanhume]

Over-volting decreases the life of the cpu because it can actually speed up the breakdown of the individual transistors on chip. On top of that, more voltage can cause metal migration (the physical traces on the chip actually break up due to high speed electrons breaking down their atomic structure).

Overclocking doesn't pose either of these, because the chip is not dealing with increased electron energy, just faster timing, which really should only increase heat output. However, you're still using more power because you are switching your devices more frequently.

edit:

And if you are wondering why there is a limit to overclocking (900 MHZ in this case) it's because you start to run into timing violations (data is attempted to be clocked in before it is ready, etc.) In that case, increasing voltage is the only hope you have of squeezing more MHZ out. A stock clocked 600 MHZ chip is capable of 900 MHZ because the ARM engineers were very conservative with their numbers, which always makes OC'ers happy.

 

[bigtruck]

Actually, that's kinda something I've been wondering about. That oh-so-famous 900 mhz estimate, is that with default voltage, or is it at the limit? Meaning, could we increase the voltage and get an even higher clockspeed?

 

[cb88]

It is within the design specs... higher than at 600mhz though otherwise the battery life would be the same

 

[bigtruck]

It is within the design specs... higher than at 600mhz though otherwise the battery life would be the same

Even at the same voltage, higher clockspeed does mean more power consumption. IIRC, energy usage varies linearly with clockspeed and with the square of the voltage. So clockspeed doesn't have as much of an effect on battery life as voltage, but it does make a difference.

I would assume that it is within spec, but I'm wondering if it's at the "the maximum allowed software voltage for the OMAP" as Squidge put it. My question still stands.

 

[anexanhume]

It is within the design specs... higher than at 600mhz though otherwise the battery life would be the same

Even at the same voltage, higher clockspeed does mean more power consumption. IIRC, energy usage varies linearly with clockspeed and with the square of the voltage. So clockspeed doesn't have as much of an effect on battery life as voltage, but it does make a difference.

I would assume that it is within spec, but I'm wondering if it's at the "the maximum allowed software voltage for the OMAP" as Squidge put it. My question still stands.


You are correct, power scales linearly with clockspeed, and quadratic with voltage.

P = fCV^2, where f is frequency, C is capacitance, and V is voltage.

My guess is that software voltage was maxed out to reach those 900+ speeds because they were specifically trying to push the units as far as they would go.

 

[MWeston]

If you take a look at the latest OMAP3530.pdf datasheet, page 103 you will read TI's recommendations on voltage and the effects on total part life.

It looks like they don't recommend any overdrive on the DSP core which is probably good since it can pull some huge current loads under maximum use.

The ARM core has more flexibility for overdrive. Standard operating mode is OPP3 which is where TI guarantees 600MHz. We have seen 625 work fine, but 650 fails so TI is pretty much bang on with their promises.

The tests at 900MHz are at OPP5 which is maximum overdrive and will come with a disclaimer that your chip life will suffer if you leave it there all the time. I would consider it more of an experimental mode and when the SGX drivers are working fully and supporting the GPL, I'd rather see a focus on getting the clock speed back down to 600MHz or less for as much as possible.

 

[bigtruck]

Thanks for the answer MWeston! For anyone who doesn't feel like downloading the pdf, here's the information about part life. I'm not going to put the whole table of operating modes and voltages and all that because that would be a gigantic quote.

To avoid significant device degradation for commercial temperature OMAP3530/OMAP3525 devices (0°C < Tj < 90°C), the device power-on hours (POH) must be limited to one of the following:
· 100K total POH when operating across all OPPs and keeping the time spent at OPP5 to less than 23K POH.
· 50K total POH when operating exclusively at OPP5.
· 44K total POH with no restrictions to the proportion of these POH at operating points OPP1 - OPP5.

So according to this, you could use it solely in OPP5 for about five and a half years of use. Still, not something I'm planning on doing. If anyone wants to read the rest of the information, here's the pdf.

 

[MilanC]

Bits of copper & thermal paste, homemade heatsink anyone?

seems to be ok without, but even better with

 

[Squidge]

You could even add a fan for good measure

 

[nubie]

I am glad somebody asked

I am happy with that, I can't see playing at 900mhz for any length of time something that requires that much horsepower (if it needs to be clocked that high, chances are it needs even more and isn't really playable).

But, I can see trying out some software that could use a little more power and running it at 800mhz for maybe 5 hours a week.

I am just happy there is plenty of power in the SGX for graphics, as MWeston said, so I don't expect to need overclocking. (In fact I would like to see Genesis with MP3 while underclocked )

 

[Squidge]

I am just happy there is plenty of power in the SGX for graphics, as MWeston said, so I don't expect to need overclocking. (In fact I would like to see Genesis with MP3 while underclocked )

Should be doable, just run the MP3 decoding on the DSP, and the emu on the Cortex

 

[MilanC]

btw, will there be a way to run an app completely on DSP, rather than just libs for ARM programs using DSP for decoding (& co.)?

 

[Squidge]

Yes, you'll be able to upload code to the dsp.

 

[olafvdkruk]

it looks pretty cool if you can overclock this divise but you also have to upgrade the ram memory if you want to be able to play better games on it