Overclocking GPU/RAM: Let's get the facts :)


Askarus

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Overclocking the CPU is nothing special as there is a nice graphical user interface for it.

Not so popular is overclocking the GPU and RAM.

See this post by Notaz which tells how to overclock the GPU/RAM.

(Thread: http://boards.openpandora.org/index.php/topic/8960-set-clockspeed-for-sgx/#entry234796 )

Currently there is a "safe" way to under/overclock it by changing system (L3) clock in latest firmwares:


sudo /usr/pandora/scripts/op_sysspeed.sh X


where X can be any value like:


332 -> 166MHz RAM, 110MHz SGX (default)


300 -> 150MHz RAM, 100MHz SGX


...


DM3730 has this set at 400 for 200MHz for both RAM and SGX (using a new divider 2 that's not in OMAP3). OMAP3 works at this setting too (SGX ends up at 133MHz because 3 is the lowest divider there) but is not stable.


As for changing SGX divider, you have to modify the driver because it overrides the divider before turning on the chip each time.
 
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Some first results:

Giga Pandroa, 1000MHz.

I overclocked from 400 to 460 (15%)

No crash so far. (470 and 480 crashed after some seconds of gaming).

On Drastic I get about 3% more performance.

I tested Castlevania Dawn of Sorrow and Castlevania Portrait of ruin.

Both about 3% faster.

Super Tux Cart:

400: 15/22/30 - 30

460: 16/18/32 - 34

PcsxReARMed:

Star Wars - Jedi Power battles:

400: 36 FPS

460: 40 FPS

PcsxReARMed:

Gauntlet Legends:

Different speed but about 3 FPS faster with 460 than with 400.

Seems like there is some effect but not much.
 
Well, For STK & PCSXrearmed, you get something like 10% performance more, so that's not too bad for a 15% speed increase. It's not linear, even when GPU is the Bottleneck (GPU+MEM I guess), other componant are playing (CPU for example), and for 15%, don't expect 15 speed increase anyway.


DraStic doesn't seems GPU driven, probably CPU limited for now, so it's gain from the MEM increased, but not much.
 
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Maybe we need a RAM/GPU stress test utility to have a standardized way to find the max overclock value that is stable.
 
Maybe we need a RAM/GPU stress test utility to have a standardized way to find the max overclock value that is stable.
Looks like the board has something new to add to the notaz wishlist. The MEM overclocking is always a welcome change. I'll test once I get my 1GHz.
 
Super Tux Cart:

400: 15/22/30 - 30

460: 16/18/32 - 34
That is a 13,3% Speed Increase for 15% clock increase. This is a big gain, almost linear (maybe even linear with a factor smaller then 1). I am curious how long this overclock can be stable. Someone said on a rebirth it worked "a few hours" until it froze the system. When we can use for 2 or 3 hours an then go back to normal speed for some time (30 minutes) and then go back to overclock speed, it would be great. Or maybe we would have to wait and shut the Pandora down for a short time. But I think most people play less then 2-3 hours without a break.
 
^

I think it's Pandora specific.

My Pandora is stable at 1200 MHz (CPU speed) and crashes at 1250 MHz.

Some can only go up to 1150 MHz and some up to 1250 MHz.

You need a Pandora and test it for you unit.

Mine crashes with 470 nearly immediately.

Was stable at 460 so far.

Didn't test it for hours.

Only some gameplay.
 
If A "system overclock", like "cpu overclock" in the PXML/OVR system would be cool, as it could enable some overclock for games that need it.

Also, some overclock for CC/Rebirth/GHz would also be cool, so overclock can be enable inside PXML'PND.

Else, everyone would have to create OVR, customized to their system (that's not a bad thing anyway).
 
That is a 13,3% Speed Increase for 15% clock increase. This is a big gain, almost linear (maybe even linear with a factor smaller then 1). I am curious how long this overclock can be stable. Someone said on a rebirth it worked "a few hours" until it froze the system. When we can use for 2 or 3 hours an then go back to normal speed for some time (30 minutes) and then go back to overclock speed, it would be great. Or maybe we would have to wait and shut the Pandora down for a short time. But I think most people play less then 2-3 hours without a break.
How long is a piece of string?   The truth is that there is no way to categorize a given speed as stable for a given amount of time,  either it's stable and will remain usable indefinitely or it's not stable and it will crash after a random interval. 

While it's true that lowering the speed does lower the probability of a crash, so there's a better chance of going longer without one, the fact remains that at an unstable speed, there's a chance it could crash at any time, and no guarantee that you'll have any given amount of time before it does.

- Neelix
 
So that's why I want some testers :) .

I'll do everything at 460 now.

We'll see if it's stable then.

Simply overclock until it seems stable.

Wait if there's some crash or not.

Then report your experience.

:)
 
On my CC and Rebirth Units I remember 380 seemed to be what I could push and be stable.
 
I would be highly interessted in mupen64 speed improvements. It used the gpu a lot and has a lot of alpha tests I think.
 
Seems better but it has no frame counter.

I can't tell you if it's only placebo or not.

Unless someone makes a comparison video I don't see any way to get some good data.

EDIT:

With 1200 MHz cou and 460 sysspeed Super Smash Bros. runs awesome.

No lagging sound and really fast.
 
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I hope this doesn't cause any long term damage.. is anybody monitoring the temp stock to overclock?
 
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