Benchmarks: Phenom X4 9950 vs Phenom II X2 555 BE @ AT Bench
At single and dual-threaded apps, it is the 555 BE hands down.
For apps that use more threads, it is easily the 9950.
For general use and gaming, most of the time (including SC2 that every new poster has been talking about) the 555 BE will perform better. Not to mention it overclocks better, runs cooler, and uses less power.
If I had a 9950, I would not think of 'upgrading' to a 555 BE.
But if I were buying now and could get a used 9950 for the same price as a 555 BE and I'm ready to overclock the 9950 to 3GHz or a little over (aftermarket cooler, etc), then I would settle for the 9950.
EDIT: Seems yasasvy beat me to the Bench link as I was composing my recommendations
http://www.anandtech.com/bench/Product/21?vs=120 X2 555 wins.
No, it does not.
It's still hard to beat 2 really fast cores fer yer basic day-to-day 'snappiness', and for most gaming.
But the thang about the original Phenoms is the clock speed. If you get a PhI to 3GHz it's gotta be in the PhII 920<->940 range, especially if you get the NB/IMC to 2400MHz (it took about 1.35v with some early ones IIRC - any more and it would fry). Here is the 555 v. PhII 920. Now look at the PhII 920 against the AII quad. Pretty damn snappy performance by yee Olde Original Phenom.
I'd buy it for $75 and tweak away on some sb7-10<->50, and fast DDR2s. Too bad it doesn't have a DDR3 controller for some 880/710 action.
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I can help provide benchmarks for the 555. Does any one here still use an original phenom?
I was using one for a server but I lent it to a friend. They are good, but the overclocking is horrible. It was a 9600 black edition and it couldn't run any faster than stock speed without raising the voltage. I tried undervolting it to see if that works, and no you can't undervolt an OG phenom.
While most processors can do at least 20% overclock on stock voltage or a 20% undervolt at stock speed, an OG phenom can do neither. It needs every bit of voltage it can get, and it generates a huge amount of heat when overclocked.
I believe my Kuma was a B3 stepping (I'm sure there were no other steppings available), and it did manage a 3.24GHz 24/7 OC. It could not manage anymore, despite the thermals being excellent (41C loaded in an airconditioned room, using the Phenom II X4 965 stock heatsink).B3 was actually decent although it couldn't match the overclock of a C2Q, they still usually managed 3.0-3.3Ghz.