Item: Intel Core 2 Extreme QX6800 - quad-core at almost 3GHz
Author: Tarinder Sandhu

Specification and pictures

The purpose of this review is to delineate how the speed increase for Intel's quad-core CPU is manifested with respect to benchmarks that stress single- and multi-threaded performance.

If you want to know what makes the quad-core SKU tick, head on over to here. The four-core part is, for all intents and purposes, two dual-core models stitched together, so head on over to here, to learn how and why the Intel Core microarchitecture took away the performance crown that was long held by AMD's Athlon 64 FX range.

However, it never hurts to trot out the high-end spec. table, just to confirm what we're looking at.

Processor name	Intel Core 2 Extreme QX6800	Intel Core 2 Q6700*	Intel Core 2 Extreme X6800	Intel Pentium E.E 965	AMD Athlon 64 X2 6000+
Form factor	LGA775	LGA775	LGA775	LGA775	AM2
Manufacturing process	65nm	65nm	65nm	65nm	90nm
Physical cores	4	4	2	2	2
Inst. per clock*	4	4	4	3	3
Pipeline stages	14	14	14	31	12
Clock speed	2.93GHz	2.67GHz	2.93GHz	3.73GHz	3.0GHz
FSB	266MHz (1066MHz QDR)	266MHz (1066MHz QDR)	266MHz (1066MHz QDR)	266MHz (1066MHz QDR)	200MHz
HyperThreading	No	No	No	Yes	No
Memory support	DDR2, 800MHz, DC	DDR2, 800MHz, DC	DDR2, 800MHz, DC	DDR2, 800MHz, DC	DDR2, 800MHz, DC
L1 cache total	128KiB data + 128KiB code	128KiB data + 128KiB code	64KiB data + 64KiB code	32KiB data + 24Kuops trace	128KiB data + 128KiB code
L2 cache total	8MiB	8MiB	4MiB	4MiB	2MiB
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
TDP	130W	130W	75W	130W	125W
Transistors	582m	582m	291m	376m	227m
Operating voltage	1.2-1.3625V	1.2-1.3625V	1.2-1.3625V	1.3-1.4V	1.3-1.4V
Current price	£620	£620**	£620	£600***	£300

* - the current Intel Core 2 Extreme QX6700 is likely to be rebadged as the Q6700. There's usually only a single Extreme Edition for either dual- and quad-core CPUs.
** - the QX6700's current price, of around £620, will also drop. No numbers as to the new pricing, however.
*** - included for comparison purposes only.

Put simply, the Intel Core 2 Extreme QX6800 can be thought of as a couple of dual-core X6800s stitched together that share a single FSB link to the system.

We had hoped Intel would be adventurous and officially launch this model with a 333MHz FSB, but we're sure that enthusiasts who opt for this multiplier-unlocked SKU will indulge in a healthy dose of overclocking, anyway. Intel has switched the multiplier up from 10x to 11x, and that's it.

We'll have to wait until Penryn and, ultimately, Nehalem, before any radical modifications are made to the core and system interface.

Our prior testing has highlighted just how well a quad-core CPU can perform if a truly multi-threaded application or heavy multi-tasking is run, and we'll be judging the Intel Core 2 Extreme QX6800 on both grounds.