What was your correction basis? I'm guessing 1/2 for half the cores, but anything else.
What are your other CPUs?
Not sure about an E2420 – is that not the name of the system?
If it is not a typo, and you may have a rare 1.8GHz dual core Intel which would not be anything special; only has 512KB cache and uses an 800MHZ FSB, (mind you, an XP 2500+ is nothing special either).

I made a list one time of my CPUs ability to crunch different work units, from different projects. I found that some CPUs were better at crunching some tasks than others, and that if I could optimise my CPUs to crunch the tasks that they were better at, I could do more work in the same time.
However such optimisations are difficult; vary from CPU to CPU, from project to project and over time; when projects change work unit type. So it would be too much work for me to do this for all the systems I have attached (about 40cores). I did this to some success on my top computers, but on quad cores it is common to find that a mix of tasks is optimal; as different projects use the CPUs in different ways. I expect this is more obvious with Hyper Threaded CPUs, but such optimisations require even greater effort.
For lesser CPUs the picture is a bit different.
It is easier to optimise, and may be worthwhile for the modest contributor. Most people would be happy to see a 5% or 10% increase in performance. You may be able to easily spot which CPUs can crunch which tasks better/faster. If you have 2 comparable CPUs, say one AMD and one Intel, and you find the AMD crunches HCC tasks 10% faster than the Intel and the Intel crunches HFCC tasks 10% faster than the AMD, then it would be clear that you should use the AMD to crunch HCC and the Intel to crunch HFCC. There is of course no guarantee you will find a situation like this. Fine if you are just comparing 2 projects, on single cored CPUs. On dual cores you would also have to compare running 2 different tasks at a time. Even at that, this is doable. However to try every possible combination of project task on a quad becomes very difficult and with 8 or 12 threaded systems it really would require you to build a database and analyse it – far too much work.
Such optimisations could only be setup and maintained by the techs, due to the variant nature of projects. Although this has been suggested, I dont think there was much uptake. So we are on our own. The techs did setup some form of CPU pairing (based on estimated performance). A positive for sure, but in a way it papers over the discrepancy in points allocation (HT systems tend to get less credit than they should) and is weakened by the way Boinc calculates CPU performance (does not use both Dhrystone and Whetstone)! Perhaps in the future they will introduce the suggested optimise check box, but it would require writing a large database and keeping it updated with CPUs and their performance running different tasks. Perhaps too much work even for the WCG?
There are online charts that compare CPUs in terms of performance. These might give you some where to statr when trying to determine the best projects to crunch for each CPU.

There are other threads on this, so perhaps this could be moved to there?

It would be useful to have an up to date list of CPU prices, running cost and Crunching performance - to help people decide what CPU they can afford.
Most existing crunchers have little use for their CPU power, so such a list would help them chose what to buy to crunch.
A basic list would serve many well, and if it included overclocked performances too, it would help novice overclockers (advanced overclockers already know what to buy and how to overclock it).
An i7-920 is a good CPU, but it requires a new motherboard and DDR3 RAM, so it is not always an easy choice upgrade and is quite costly ($400+).
Someone with a single or dual core would probably find that the easiest and most affordable upgrade path is just to upgrade their CPU. For example someone with an old-ish 4200+ could just put in a quad Athlon and double their contribution for under $100. Someone with an E7200 might be able to use a Q9650.
The 45nm socket AM3, 6core AMD CPUs are actually overdue by 3weeks – so any time soon.
The Phenom II X6 1035T, Phenom II X6 1055T, and Phenom II X6 1090T are due to be clocked at 2600, 2800, and 3200MHz respectively. The CPUs are essentially just the same as existing AMD Phenom II CPUs but with 2 more cores, so they should crunch 50% more roughly.
The speeds are slower than the top 6core i7, so these CPUs are not likely to be competing with the 6-core i7. However they should compete directly with the i7-920 through to i7-950 and outperform any skt 775 processors. This should cause healthy competition and make many upgrades possible.
On the face of it a 6core 3200MHz Phenom II might sound like an attractive upgrade route for my Phenom II 940 (4 X 3.0 GHz); a 60% increase in performance. However I have an AM2+ motherboard, not an AM3 board, so it is a non-starter!

This is a list of CPU crunching performances for Folding@home. Although it is not identical, it should give a fairly accurate performance guide.
These benchmarks were mostly taken from various pages on http://www.xbitlabs.com/ so thanks for doing these benchmarks.

Folding@home benchmark, CPU

5265 Core i7-975
5063 Core i7-965
4862 Core i7-950
4662 Core i7-940
4263 Core i7-920
3999 Core 2 Extreme Q9770
3547 C2Q Q9550
3307 C2Q Q9400
3294 Phenom II X4 955
3103 Phenom II X4 940
3063 C2Q Q8300
2908 Phenom II X4 920
2848 C2Q Q8200
2540 Phenom X4 9950
2754 Phenom II X4 910
2727 Phenom II X4 810
2635 Phenom II X4 805
2291 Phenom II X3 720
2171 Phenom II X3 710
1875 IC2D E8400
1872 Phenom X3 8750
1814 IC2D E7500
1755 Phenom II X2 550
1741 IC2D E7400
1734 IC2D E6300
1698 Phenom II X2 500 Callisto
1687 Athlon II X2 250
1687 Athlon II X2 200 Regor
1650 IC2D E5400
1644 IC2D E5200
1589 Celeron E3300
1572 Athlon X2 5000 Kuma
1544 Celeron E3200
1479 E2220
1391 Athlon X2 7850
1364 Athlon X2 6000 Windsor
1307 Athlon X2 6000 Brisbane
1248 Athlon X2 5600
0797 Celeron E1600


Some Overclocked benchmarks:
4366 C2Q Q9300 @ 3.56GHz
4301 C2Q Q6600 @ 3.60GHz
4262 C2Q Q8300 @ 3.56GHz
3814 Phenom II X4 920 @ 3.72GHz
2485 IC2D E5400 @ 4GHz
2460 IC2D E7400 @ 4GHz
2164 Athlon II X2 250 @ 3.9GHz
2136 Phenom II X2 550 @ 3.8GHZ

I moved this here from elsewhere as it got no comments or additions there.

There are presently two AMD 6-core CPUs; 1090T (3.2GHz), 1055T (2.8GHz).
A further 2 are set to be released soon; 1075T (3.0GHz) and 1035T (2.6GHz).
Given their CPU architectures and other benchmarks I would estimate their folding benches as,

4941 for the 1090T

4500 for the 1075T

4360 for the 1055T

4050 for the 1035T

So for crunching, the 1090T is approximately as good as an i7-950 (natively clocked), and costs about 50% less!
Similarly, the 1055T roughly matches the i7-930 (not on the list) when it comes to crunching and costs about 50% less.

With the AMD price structure, these are attractive cores for crunchers, especially when you consider that their motherboards tend to be slightly less expensive and these can be used to update existing quad core AM3 CPUs.

However, for non crunching the i7's typically outperform the 6core AMD's and the i7-980X is much better for crunching than the 1090T, containing many improvements over the earlier i7 range - It would probably benches close to 8000!
Although you could build a full 6 Core AMD system, or 2 base units, for the price of an i7-980X, the i7 does much more work, about twice that of the forthcoming 1035T.

Food for thought,