a weak IMC may begin exhibiting problems at higher CPU clocks, even though it appeared fine in the previous section. A 300MHz memory clock may be perfectly fine at 2.1GHz, but at 2.6GHz, the behaviour may be different altogether.
The article is touching on the IMC [integrated memory controller] inside the CPU. For a stable system and a good OC, you need to test each successful OC using a few benchmarks. Due to all of the variables, FSB, CPU speed, RAM speed, IMC speed and HTT link speed...it can get very touchy trying to maximize all of those things together.
It then goes on to say..
I immediately recognized that 10x261 was perfect for the BH-5, as it had no issues pumping out 261MHz at 2-2-2-5 timings, and this is very close to it's maximum clock speed at the voltages I tested with. If this proves to be stable, we are literally getting the best of both worlds.
In a perfect world where every chip has a perfect IMC, 9x290 would have been a great choice for my TCCD. Unfortunately, 290MHz is not going to happen with my Winchester and 1GB of RAM, so I will likely have to use 11x238MHz and take advantage of the tighter 2-3-3-6 timings it is capable of at that speed. I could also use 10x261MHz for the TCCD but it only proved stable with rather loose 2.5-4-4-8 timings. 11x238MHz at 2-3-3-6 timings is still a better choice. Hopefully this will prove to be stable with a 2.6GHz CPU clock.
Faster RAM is always good...but not at the cost of too much latency from loose timings. So, 'he' is determining the fastest RAM clock speed, according to the maximum CPU clock he can run. Since ~260mhz is close to the max speed for his RAM..he is choosing a 1:1 ratio to keep the highest CPU clock and the highest RAM speed. If his RAM was capable of a little more speed..he couls easily run the 5/6 divider, to still have a 2.6ghz cpu...but with his RAM only at ~231mhz...he would still have some room to OC his CPU, more, before the RAM reached its limit of ~260mhz again.
The point is to find the best combination for your OC..(highest CPU speed + lowest timings/fastest speed, for your RAM) If stability becomes and issue, you can adjust your CPU multi, to change the dividers/speed ratio, or lower your HTT freq.
to calculate your divider, take the FSB base clock, if at 250mhz FSB using a 3/4 divider.. you do the foolowing :
(250 * 3) / 4 = RAM speed of 333mhz...or ddr 667 <-maxxed out RAM speed
(250 * 4) / 5 = RAM speed of 312mhz...or ddr 624 <- RAM still too fast!
(250 * 5) / 6 = RAM speed of 208mhz...or ddr 416 <- Good divider!!
...are you understanding somewhat now?