Winging a Pi 3 overclock

[Nickcn]

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[GTR2Fan]

NOTE TO NOVICES: PLEASE DON'T ATTEMPT ANY OF THIS UNLESS YOU HAVE MADE A BACKUP OF YOUR SD CARD AND ARE CONFIDENT THAT YOU UNDERSTAND ALL OF THE TERMINOLOGY USED. I TAKE NO RESPONSIBILITY FOR ANY INCONVENIENCE OR DAMAGE CAUSED BY FOLLOWING ANY OF THE ADVICE GIVEN IN THE FOLLOWING POSTS.

It helps. 500MHz should be doable as that's worked on nearly every Pi2B it's been tried on so far. Please tell me you have a heatsink.

Yes. It's worth overclocking the RAM too. 600MHz may not be achievable. You certainly won't get there without the magic schmoo incantation.

[Nickcn]

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[Nickcn]

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[GTR2Fan]

Gopher it!

Adding...

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sdram_schmoo=0x02000020

...to config.txt will help RAM stability above 500MHz.

[Nickcn]

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[GTR2Fan]

Greater memory bandwidth. It's worth it on the quad-core Pis where memory bandwidth may become more of a bottleneck than on the old single-core Pis.

[Nickcn]

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[GTR2Fan]

Yes, but you'll need to raise the RAM voltages as well. If it refuses to boot then you may have to edit config.txt on your PC to lower the speed a little, so be prepared.

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sdram_freq=600
sdram_schmoo=0x02000020
over_voltage_sdram_p=6
over_voltage_sdram_i=4
over_voltage_sdram_c=4

...may work.

[Nickcn]

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[GTR2Fan]

That would be a good idea. It's probably easiest to test the RAM first with memtester. I can't remember whether it's a standard part of Raspbian Jessie or not, but you can soon install it with...

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sudo apt-get install memtester

... if it's not there.

I believe you're running with GPU memory of 256MB, but you should still be able to test around 700MB of it without lowering that with...

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memtester 700 1

...which will send it around one loop of extensive RAM tests. If it fails, knock the speed down a little. If it passes then run it at least another 5 times to be absolutely sure with...

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memtester 700 5

That should keep you busy for the next few hours.

That CPU test is OK for starters, but a thorough workout of the CPUs and GPU together will be the ultimate test. That's why I mentioned Quake 3 Arena previously. It succeeds in crashing a borderline overclock where many stress tests fail.

[Nickcn]

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[GTR2Fan]

For the RAM, there's no adequate substitute for memtester that I'm aware of.

[Nickcn]

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[GTR2Fan]

You're welcome. I'm probably as keen as you are to see just how far it can go with complete stability.

[Nickcn]

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[Nickcn]

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[GTR2Fan]

It would be better to temporarily lower your GPU RAM to 64MB so you can test more of the RAM really.

[Nickcn]

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[Nickcn]

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[GTR2Fan]

You could try pulling the RAM voltages all down by 1 first to see if that fixes it, so 5/3/3. If it doesn't then you're probably going to have to back the speed off 10MHz at a time until you achieve stability with either 5/3/3 or 6/4/4 as those seem to be the most typical voltages for stability close to 600MHz.

It's a fine balancing act squeezing out the last few stable MHz. Don't be too disappointed if 600MHz is out of reach as the RAM is only manufacturer rated at 400MHz.

[Nickcn]

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[GTR2Fan]

Yep. Give it a go. I believe millhouse had better luck than me at 5/3/3 than at 6/4/4. The window for operating voltage can become very narrow close to the limits of a RAM overclock, so going down might fix it. I wouldn't recommend going up any higher than 6/4/4 as it probably won't help anyway and may have long-term impacts on longevity that very few will have explored yet.

[Nickcn]

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[Nickcn]

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