Intel Pentium Extreme Edition 955What's new about Intel's Extreme Edition 955 processor, then? Let's trot out the specification's table and compare it against some healthy competition from both Intel and AMD's high-end CPUs.
|CPU||Intel Pentium Extreme Edition 955||Intel Pentium Extreme Edition 840||Intel Pentium 4 Extreme Edition 3.73GHz||Intel Pentium 4 670||AMD Athlon 64 X2 4800+||AMD Athlon 64 FX-57||AMD Athlon 64 4000+||Form factor||LGA775||LGA775||LGA775||LGA775||S939||S939||S939||Manufacturing process||65nm||90nm||90nm||90nm||90nm||90nm||90nm/130nm||Cores||2||2||1||1||2||1||1||Clock speed||3.46GHz||3.2GHz||3.73GHz||3.8GHz||2.4GHz||2.8GHz||2.4GHz||FSB||266MHz (1066MHz QDR)||200MHz (800MHz QDR)||266MHz||200MHz||200MHz (driven clock)||200MHz||200MHz||Hyper-Threading||Yes||Yes||Yes||Yes||No||No||No||Level2 cache||4MB (2MB per core)||2MB (1MB per core)||2MB||2MB||2MB (1MB per core)||1MB||1MB||ISA||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE3||x86, x86-64, SSE-SSE2 (130nm)||Thermal Design Point (TDP)||130W||130W||110W||115W||110W||110W||89W||Operating voltage||1.2v-1.3375v||1.3v||1.3v||1.3v||1.35v-1.4v||1.4v||1.5v (130nm)||Transistors||376m||230m||169m||169||233m||114m||105.9m||Virtualisation Tech||Yes||No||No||No||No||No||No|
Take a look at our original review of the Intel Pentium Extreme Edition 840 here to get a grounding of what makes Intel's dual-core CPUs tick. In this review, we'll be concentrating on the main differences between the '955 and previous range-topping '840.
What's the same?
Architecturally-speaking, both the EE '955 and EE '940 use two independent cores that are housed in one physical processor package. Each core has access to its own L2 cache, but both cores share a single bus interface to the chipset's Memory Controller Hub. Given the use of a 266MHz FSB, that's a potential 8.528GB/s that has to be split between the two processors. When dealing with dual-core Intel CPUs, then, more system bandwidth is always a good thing. We'll be seeing each core packaged in a single CPU under the codename of Cedar Mill. It will, most likely, be the last Pentium 4 single-core model.
It's of no surprise that the '955 is a regular LGA775 CPU. It's designed to work best with Intel's i975X chipset but the word is that most i955X-based motherboards, and most LGA775 boards for that matter, will be able to accommodate it via a BIOS update. The 65nm manufacturing process should lead to lower heat outputs but Intel continues to state a thermal design point of 130W, making the Presler another hottie under the silver heatspreader. Hyper-threading support is intact, naturally, so we're looking at the 4 logical execution units split over the two independent cores. Other Intel features such as Execute Disable Bit (buffer overflow protection) and EMT64 (64-bit addressing and larger memory support) are also present, obviously.
65nm manufacturing process
The E.E. 955, codenamed Presler, is manufactured on Intel's advanced 65nm process. Manufacturing on a smaller process has a number of benefits. Firstly, basic maths tells us that with a smaller manufacturing process, Intel can fit more cores on a wafer of a given size, leading to cheaper-to-produce CPUs. Another benefit of having two separate cores in one package is the ability to choose cores from different parts of a wafer. Indeed, there's no reason why two identical cores from separate wafers cannot be used together. As mentioned, a 65nm manufacturing process should, ceteris paribus, lead to lower operating voltages and, consequently, heat. Intel's documentation states an operating VID of between 1.2V-1.3375V, down from the 1.3V from its 90nm-based CPUs. Brand-new processes are often the harbingers of high overclocks, and we managed a rather tasty overclock with our sample.
3.46GHz clock speed, 266MHz FSB
A reduction in manufacturing process wouldn't be enough of an incentive after seven months of the Extreme Edition '840, would it? Intel has increased the '955's clock speed to 3.46GHz, accomplished by running a 13x multiplier with a 266MHz FSB (1066MHz QDR). That makes it just over 8% faster than the '840 in pure clockrate, although the faster FSB speed should add a little extra performance spice. Intel needed a faster FSB to keep the dual cores saturated with data at all times, and 266MHz matches the Pentium 4 3.46GHz (Gallatin core) and 3.73GHz's (Prescott-2M). We should have seen the '840 launch with a 266MHz FSB, really.
4MB L2 cache
Yep, you've read that right. The Pentium Extreme Edition 955 packs a whopping 4MB of L2 cache, split into 2MB chunks for each core. That makes it the most cache-rich consumer-level processor ever. Extra L2 cache allows more data to be stored in super-fast on-chip memory for quicker accesses when requested. We'd expect gaming performance to benefit here, along with other programs with large data-sets. The physical cost of carrying so much cache is a 376m transistor count, up from the 230m or so present in the '840. The financial cost of 4MB L2 cache is an asking price of around £750.
Intel Virtualization Technology
Quietly slipped in mid-November for a couple of its single-core 600-series processors (named 662 and 672), Intel's Virtualisation Technology offers the opportunity of running multiple operating systems in independent partitions on a single platform at the same time. The current status quo is that in a non-virtualised system, a single operating system has access to, and controls, all the hardware facets. With Virtualisation Technology and in conjunction with a software layer that apportions hardware resources to each operating system (Virtual Machine Monitor), a single platform can effectively function as several 'virtual' machines, with each running a different operating system and each sharing the platform's hardware resources. It's possible to virtualise a machine now through pure software, with VMware coming to mind. Intel's opted to implement it on a hardware level, with VT-enabled processors carrying 10 new Virtual Machine Extensions. It's an interesting concept that's been developed from server-based platforms. We'll be taking a thorough look at VT tech. in a separate article.
A smaller manufacturing process, more speed, and bags more cache will make the Intel Extreme Edition 955 faster than the CPU it replaces as the performance dual-core model. You'll have to read on to see just how fast.