Pentium 4 670:
We've also got a Pentium 4 670 in the labs; it's clocked at 3.8GHz with an 800MHz front side bus, which makes it the highest-clocked Pentium 4 that Intel will ever ship - does that mean it is the fastest though? We'll attempt to answer that question by time you've finished reading this article.
There are a number of new features in the 600-series Pentium 4's over the previous 500-series Pentium 4 CPU's. The 600-series introduced more L2 cache, taking the total L2 cache from 1MB to 2MB meaning that there is more on-chip memory for the CPU to utilise when accessing data from the thread (or threads) that are being executed. There is also the power saving features that we mentioned above - the 600-series has C1E, TM2 and Enhanced Speedstep technologies embedded in to the architecture.
C1E is the most interesting of the bunch - it works similarly to AMD's Cool 'N' Quiet technology. It drops the CPU's multiplier and operating voltage when a halt command is issued - once an application demands CPU power, the processor returns to its default performance clock speed just like it would with AMD's Cool 'N' Quiet technology. Finally, there's also the inclusion of 64-bit extensions which allows the 600-series CPU's to run a 64-bit operating system such as Windows XP x86-64.
Pentium D 820 on the left, Pentium 4 670 on the right - we told you there were differences!
Cosmetically, there is very little between the two CPU's - obviously, there are differences underneath the Integrated Heat Spreader but you'd not be able to tell the pair apart. There's clearly no difference between the two processors in the photograph of the two heat spreaders on the previous page, but the photograph showing the female array of LGA775 pads shows some distinct differences between the two.
The transistors in the centre of the CPU are arranged in a different way with all transistors lining up in one direction on the Pentium D. The Pentium 4 600-series has an interesting array of transistors that follow no clear pattern. There are also some slight differences between the pads to the right hand side of the transistors in the centre.