Exclusive: Retail Core i7 CPUs More Powerful than Originally Reported

Posted 03/04/2009 at 8:00pm | by Gordon Mah Ung

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If you’ve tried to research the differences between Intel’s top-end Core i7-965 Extreme Edition and the midrange 940 and budget 920 parts, you’re probably as confused as us. And we even have direct access to Intel. But the technical differences between these parts are enormously important for system builders when you consider the price disparity -- $1000 for a Core i7-965 compared to under $300 for a Core i7-920.

What we do know is that the Core i7-965 has unlocked multipliers going up and down (although we have to point out that we have not seen any motherboards with multipliers that let you actually set it higher. You can only do that by increasing the Turbo Mode ratio.)

One other known fact is that you cannot set the Turbo Mode ratios on the 940 and 920. OK fine. But what else is different? Intel told us as recently as two months ago that the QPI was locked at 4.8GT/s to prevent you from running it at the Extreme’s 6.4GT/s speed. Memory ratios, however, are supposed to be unlocked.

But maybe not.

Our experience with no fewer than three Core i7-920 and 940 chips said otherwise. On these chips, even though you could set the ratio manually in the BIOS for DDR3/1600 or DDR3/1333, the RAM was actually locked at DDR3/1066. We also verified on these chips that the QPI was locked t 4.8GT/s and we had no access to the Turbo Modes. Right, so no Turbo Mode settings, locked QPI and locked memory. Got it, check. Move along.

So where’s the mystery? We recently acquired a retail, boxed Core i7-920 CPU. It was used for a photo shoot and was subjected to extreme heat and smoke damage and had a set of car jumper cables clamped to it. Dead right? Actually no. The processor functions fine but in messing with it, we discovered that the memory ratios were unlocked. Set the RAM at DDR3/1600 and it actually runs at that speed! What the hell? Did we somehow find the secret to unlocking Intel’s Core i7 – just hook it up to car jumper cables? We wish.

With an engineering sample 920 in place, you have but one QPI speed available but populate the board with a production 920 and voila, you get three choices.

After talking with Intel as well as some back channel contacts we had, we learned that the memory multipliers on production CPUs are unlocked. The reason our CPUs had locked multipliers, we were told by Intel, was because they are engineering sample chips. Engineering sample parts are pre-production CPUs provided to the media, OEMs, motherboard makers and various other hardware vendors to test and bring up components. These CPUs, we were told, are locked.

Huh? To make matters worse, while mucking with our retail Core i7-920, we discovered that our QPI speeds were also unlocked. We could set it to 6.4GT/s all day. Our back channel contact tells us that after some digging, it was discovered that yes, that’s the way it’s supposed to be. QPI is supposed to be 4.8GT/s but you can run at it 6.4GT if you want. Wha, what? But two months ago, Intel insisted that QPI was locked. Now we’re told that QPI is unlocked. Confused? We are.

But why lock them, and only on engineering sample parts? Traditionally, Intel’s engineering parts are unlocked so vendors can perform various tests. This is why engineering sample parts sometimes have higher values: they often have no artificial limiters on them.

Intel’s official reason for the change of heart is: “We made a marketing decision to unlock them for the launched product due to requests from some of our customers.”

Who are the customers? Intel didn’t name names but our first guess was memory makers. If memory support for DDR3/1600 was only limited to $1,000 CPUs, they wouldn’t sell a lot of high-end memory. Perhaps some OEMs even balked as well at the thought of selling machines with RAM limited to DDR3/1066.

Even though the board lets you set a memory ratio of 6 for DDR3/1600, it’s not running at that speed. 

That’s evident if you look at the POST screen. Here you can see that the RAM is still running at DDR3/1066.

Ultimately we don’t know why Intel decided to do it this way but at least the results helps out the budget buyer and frankly, makes the budget parts even more attractive. So, to sum up, Core i7-920 and Core i7-940 parts have:

• Locked multipliers so you cannot exceed their rated top speed (without overclocking the base clock).
• Locked Turbo Mode multipliers so you cannot make fine-grained adjustments to the Turbo Mode features.
• Have unlocked QPI speeds but are officially rated for 4.8GT/s.
• Have unlocked memory multipliers so you can select from 1066/1333/1600/1866 and up.

The board doesn’t seem to know the difference between a locked or unlocked memory multiplier as the production 920 memory ratio setting looks exactly the same.

But reboot and it’s obvious that it is working as it is intended. Here the POST screen shows tri-channel at DDR3/1600 speeds.

Hopefully this helps clear up some confusion around this. If you’re still not sure that your RAM is operating at speed we recommend that you first double check the RAM multiplier in the BIOS and that it is set for, say DDR3/1600. Then download CPUZ from cpuid.com and click on the memory tab. Finally, download a memory benchmark such as Sisoft Sandra and make sure that gives you the result you’re expecting. If you find that Sandra does not show any increased bandwidth going from DDR3/1066 to DDR3/1600, your CPU has a locked memory multiplier and is simply ignoring what your motherboard’s BIOs is saying. In this situation, you’ll want to take it up with the vendor who sold you your CPU.

As final proof, we see that the DDR3/1600 speeds show up in Everest Ultimate and CPUID shows that the RAM is running at speed.