Intel Clarkdale CPU Overclocking With IGP Enabled - Reaching High BCLK
 

Since the launch of the new CPUs from Intel, nicknamed Clarkdale, we have seen a fair share of overclocking attempts; some people even breaking world records, pushing the a Clarkdale over 7Ghz. We have read reports from overclockers who had issues with pushing the BCLK higher when the IGP was enabled. In this article we will explore possible solutions to help circumvent this limit, so you can enjoy high BCLK while using the IGP.

http://www.madshrimps.be/gotoartik.php?articID=988

Attaching the screenshots of the "721MHz frequency testing". Warning ... a lot!

As far as I can understand how the IGP frequency is made, the IGPbase frequency is not function of BCLK, but of BCLK/4.

So:

IGPbase = 133*multiplier/4

or

IGPbase = 33*multiplier.

The multiplier itself is one value ... officially.

Straight from Intel datasheet:

//edit: added second one.

011000binary makes 24decimal, 24x33 gives 800 :)

It seems that the clock frequency of the Intel GMA can vary between 166MHz and 900MHz. For desktop CPU's, that's 733 and 900 only, for mobile the igp frequency is automatically decreased when turbo mode is enabled and you're running high load CPU applications. So:

166 = 33 x 5 = 000101b
200 = 33 x 6 = 000110b
233 = 33 x 7 = 000111b
266 = 33 x 8 = 001000b
300 = 33 x 9 = 001001b
333 = 33 x 10 = 001010b
366 = 33 x 11 = 001011b
400 = 33 x 12 = 001100b
433 = 33 x 13 = 001101b
466 = 33 x 14 = 001110b
500 = 33 x 15 = 001111b
533 = 33 x 16 = 010000b
566 = 33 x 17 = 010001b
600 = 33 x 18 = 010010b
633 = 33 x 19 = 010011b
666 = 33 x 20 = 010100b
700 = 33 x 21 = 010101b
733 = 33 x 22 = 010110b - DESKTOP
766 = 33 x 23 = 010111b
800 = 33 x 24 = 011000b
833 = 33 x 25 = 011001b
866 = 33 x 26 = 011010b
900 = 33 x 27 = 011011b - DESKTOP

IGPclk = IGPbase x (BCLKset / 133) MHz

Now: IGPbase = (BCLKset / 4) x IGPmp

Thus: IGPclk = (BCLKset / 4) x IGPmp x (BCLKset / 133) MHz

Or: IGPclk = (BCLKset² x IGPmp) / 533 MHz

That looks weird :p

When looking a the desktop datasheets, I'm a bit confused, though.

A bit more testing: 100MHz and 200MHz BCLK:

1200 * (100/133) = 902MHz
600 * (200/133) = 902MHz

Performance: 5525 vs 5435

Don't make clock dividers over-complicated ;)
PS home tomorrow?