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The Stilt's findings on BCLK finetuning (improve Llano BCLK)


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All credit of the findings goes to The Stilt.


I´ll say that the high BCLK "issues" (if 75% overclock can be seen as one) are either clockgen programming or "strapping" related.

In clockgen programming there isn´t any obvious faults tho


I think Asus resets certain frequencies (PCI-E, PCI, USB) at certain pre-programmed BCLK frequencies.

The software straps (timing latch) excist only up to 110MHz BCLK... I guess they did not think anyone would go higher...

After that the timings remain the same, only the delays are calibrated.


It was quite a rumble to find the correct sequence:


1. Set the BCLK to 161MHz, save and exit.

2. Enter setup again, set 166MHz BCLK, save and exit

3. Enter setup yet again and set 170MHz BCLK, save and exit...


EDIT: Forgot to mention, in case the system crashes for any reasons and it does not post straight away, you need to start again from step 1.


Going higher probably requires on the fly adjustment until we get a bios with GPU clock control


Yeah I know, for me 155MHz BCLK works, so might 156MHz. 157,158,159,160MHz fail..

161MHz start is the key The frequencies between 161MHz and 166MHz fail too, yet 166MHz works.


In case the system boots but crashes or freezes when Windows has been loaded, bump up the VDDNB a bit.

This is because the SCLK and UVD clocks raise too... Even without 3D application running the clocks can spike up temporarily which will freeze the system as the SCLK and UVD are too high. On A8-3850 the SCLK & DCLK will be at 1020MHz, VCLK 1224MHz when the BCLK frequency is 170MHz.


It is a lot easier to reach high BCLK with a locked APU on Asus.

In case the APU is unlocked the CPU must be able to INIT at ~5.3GHz.

Thats because Asus is using reduction divisors (/2) with <23x multipliers...

This means the CPU inits at 32x170 before the reduction divisor kicks in.

Thats why I had to start alot lower and watch out for cold boots.


Original post: http://www.xtremesystems.org/forums/showthread.php?273612-What-s-the-current-Llano-APU-vantage-wr&p=4930635&viewfull=1#post4930635

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  • 4 weeks later...

Uhm... my best bclk was obtained while I was testing how far could the gpu go, with cpu and ram lowered in frequencies.

I arrived@171 or 173, don't remember precisely, but couldn't use that freq togheter with high rams and cpu so it was, let's say, useless for the competition ;)

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