What about this bus-locking thing?

We all know that Intel has been "Clock-locking" these CPUs for a while now. For the un-initiated, clock-locking sets the multiplier at a specific level which can not be altered. In the case of the 300A, this is 4.5 because the chip is supposed to run on a 66Mhz bus (4.5x66=300).

This limited our tweaking to changing the FSB, or Front Side Bus speed of the motherboard where our chip was planted. In the case of the Celery 300, this meant 100Mhz and, presto (in most cases) we suddenly had a 450Mhz CPU for the price of a few large pizzas!

A few weeks ago rumors began circulating that processors after a certain week, usually about 47 or 48, were also bus-locked. This would mean, if it were true, that we wouldn't be able to change anything and that overclocking would be effectively dead.

I've tested processors now thru week 51 and have seen no evidence of this at all. In point of fact, the 400A I tested this week was listed at another site as one that was definitely bus-locked and yet it was not.

I believe that, so far at least, what has happened is that garden-variety overclock failures are being reported as bus-locking. With the stiff competition to be first with "breaking news" among web sites, these reports are being instantly published without verification.

Until I get one on the bench that is bus-locked, I'm assuming that this rumor is just that; a rumor, and nothing more.

Now, a little about the Celery cooking process. Those of you have read previous Celery reports can feel free to skip this section, but I include it for complete and utter disclosure's sake.;-)

Sauteing the Celery.

I test each CPU under initial identical conditions prior to "burning in" my combos. I do an initial test run using the same Abit BH6, same RAM (single stick 64MB Micron, CAS3) and the same video card, a Trident 975, 4MB AGP. For those who are interested, this is a very fast 2D card that consistently scores better than 5 in Final Reality. Not very good in 3D, but for a business system, it’s a screaming bargain. I use an old 270MB Quantum hard drive (actually have 3 set up identically, so I can burn multiple combos at once). I use an old hard drive because I assume that these setups will be going in to a variety of situations with a variety of drives and that if it’ll work with this clunker, it’ll probably work anywhere.

I run a quick test at 450 using Business Winstone 97. Why such an old version, you might ask? Because I’m not testing for performance, only stability. This works perfectly for that purpose. If it fails, I bump the core voltage up a notch until it passes. If the CPU won’t do 450 or requires more than 2.2v core, I set it aside for later evaluation. After passing the first test on my evaluation board, I move the chip to the motherboard with which it will be mated.

I put each one through 6 full rounds of Winstone and 2 hours of Final Reality. By using these two tests, I’m covering both the 2D business users and the 3D gamers. As an aside, for those who haven’t used it, Final Reality is not only a great test, it is visually stunning. One glitch at current voltage, and it’s bumped up a notch, until it’s completely stable. Because I believe that stability means having a little breathing room, I don’t sell a chip at 450 if it requires more than 2.2v core to stabilize.

Index Thrashing the 400A