MSI 850 Pro2 - extreme P4 overclocking!

Extreme overclocking / II

Processor requirements

Hirdetés

Okay, we have one of the boards above (we actually did, out of the four hardware we mentioned, two were these two mainboards) and are ready for some serious action. We plug in our fresh and new 1.7GHz P4, set the FSB to 133MHz, scale back the RDRAM, save the settings in the BIOS and reset... and... and... black screen. Okay, we reset the CMOS, dive back to the BIOS settings and start scratching our head: what happened? The solution is simple. 17 x 133MHz = 2260MHz, which is simply too much for a 1.7GHz part. This means we have to experiment with a lower clocked P4 to achieve better results. Why not try with a 1.4GHz part? Sure. 14 x 133MHz = 1866MHz, which is also way too much for most 1.4GHz P4s. Most, but not all! What is the differentiator then? To put it simple, if we somehow received a 1.4GHz P4 that in reality had a 1.7GHz core, but was labeled 1.4GHz, for any reason, we would be almost sure to reach 1866MHz. Sounds great, but why would anybody, especially Intel, label a 1.7GHz part for only 1.4GHz, when 1.7GHz makes them more money? The answer is simple and Intel has been doing this ever since they existed (remember those SL2W8 P2-300MHz CPUs, that could do 450MHz with default voltage?).

As time passes, the production of a certain CPU surely yields higher output. Production lines get better, new steppings are introduced, etc. Stepping is the key word here. Stepping stands for the revision of the silicone used in the chip. Higher stepping number/code usually means that a few things have been patched, produced heat has been lowered and yields/frequencies are better. Think of it as a new BIOS revision (ie: for a mainboard). But what happens when a newer stepping allows Intel to produce all P4 CPUs at or above 1.7GHz, but there is still serious demand for lower speed parts? Should Intel get back to older production lines? No way, costs would raise without any benefits! Should Intel lower the price of the 1.7GHz part all the way down to 1.4GHz, for example? For us, that's a yes, but for Intel, certainly no, as they would lose a lot of money from people who would have bought the 1.7GHz part for the original (high) price. The only - profitable - solution is to satisfy demand with 1.4GHz chips, even if all chips are 1.7GHz by nature :). So, the multiplier lock kicks in and a CPU with a newer stepping and a "could-have-been" 1.7GHz core is released, at 1.4GHz, with a 14X multiplier. These are the CPUs we are looking for! They cost you "only" 1.4GHz, but are 1.7GHz inside and will probably run with our new boards at 133MHz FSB at 1866MHz. Take a look at the table below, taken from Intel's site:

One immediately notices, that there are only two steppings for all CPUs, one being B2 and the other (newer) C1. If you recall, P4 was originally released as 1.4 and 1.5GHz, with 1.3GHz following LATER! The B2 stepping is only available up to 1.5GHz and as it is the older one, it is safe to guess that original P4 CPUs were based on this core. Thus, buying a 1.3GHz part (in case it's cheap) makes perfect sense as it is from the same stepping as the original 1.5GHz CPU. It was even introduced later, probably for demand reasons, so being able to run it at 1.5GHz is almost certain. Please understand, that overclocking isn't independent of luck, as chips from the very same batch with the very same stepping all overclock differently. But not very differently. If someone has a P4 1.4GHz running at 1.9GHz, it's not because he was so incredibly lucky, but because he has a CPU with the newer stepping that was downgraded by Intel AND he was lucky to get a good part from those. Crazy high overclocks (let's forget extreme cooling methods now, with a better stepping, they also do better) always attribute to "tricks" like this.

Which one is the right P4 to get then? Well, just take a peek at the C1 stepping! ALL current P4 processors are available in the C1 flavour and man, what a flavour that is! Even the 1.8GHz part is using C1. Our theory is partially proved here, as Intel was fine with producing 1.3-1.5GHz CPUs with B2, but for some reason they later introduced these CPUs with C1 as well (B2 is probably no longer being produced, at all). Does this mean that a 1.3GHz P4 labelled SL5FW has a 1.8GHz core, for sure? Probably yes, although production does work by sorting the CPUs in categories after they have been pre-tested by Intel. As always, there are some faulty ones and others just don't make it to 1.8GHz and have to be downgraded. But in the long run, C1 stepping CPUs are all based on the highest core produced with that stepping. To make sure you are in the "long run", try to select a CPU with the correct sSpec AND the highest production week possible (more one this later).

A cikk még nem ért véget, kérlek, lapozz!