Second 4890 with phe II x3 720?

Hello together

Approximately one year ago I built a system with a phenom II x3 720 a Corsair tx-650 Psu and a His hd 4890.

I got a relatively good offer for a used XfX 4890 Hawx (100.- instread of 180.- which is the retail price) and I'm asking my self if it's worth buying it. My motherboard can run them in x16 x16 mode (ga-ma-790fxt) but I think that my Cpu will be to big of a bottleneck. What do you think should I buy the second GPU?

I originally planned to upgrade to bulldozer but since AMD said that bulldozer wont be compatible with Am3 I'm stuck with this CPU.

I've already tried overclocking this CPU and could only reach 3.5 Ghz at a too high voltage of 1.45. At the moment I'm running at stock speeds and I don't want to overclock it higher then to what it reaches with stock voltage because I fear that this would be too much for my already one year old Psu.

Thank you for your thoughts

Kind regards Erdinger

Edit: I play at 1920x1080 res and want to keep the Pc for at least one more year and probably two
5 answers Last reply
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  1. it should be fine

    what psu have you got

    the absolute max voltage for a 720 is 1.55 i had to go to 1.52 to hit 3.8 on my old 720

    or just sell it and get a 955
  2. My Psu is a Corsair CMPSU-650TX, 650W it has only two pci e x6 connectors but I can use molex to Pci-e converstors for the 4890 xfire (just like the moderator did in a system builder marathon with the same PSU and GPUs).

    The absolute max overclock of my CPU is 3.54 Ghz I really tested averything possible and it won't go any higher also after one year it even got unstable at that speed which is why I am running at stock speed again.

    I don't think anyone would want to buy my CPU and don't want all that stress. I would really love to upgrade to bulldozer but AMD screwd me over by first confirming it would be AM3 compatible and now saying the opposite.

    All 4890 xfire tests I read are made with Core I7-920s at 3.8 ghz so I really don't know if its worth for me to upgrade
  3. hmm really? I thought that only an overclocked I7 wouldn't bottleneck it.

    I'll do some research on the building a balanced gaming rig articles here on toms and see how much the 4870x2 benefits from four cores that are faster then mine.

    Anyone with another opionion or a good link for me?
  4. Yeah, just find a nice stable overclock and you'll be good. Even if it's slowing it some there should still be a large enough increase in general to make it worth it.

    My 720 is running at 3.2 stock voltage. I just did it for the heck of it, my card is a HD 4850, so it didn't need the boost.

    The tests that they run like that, with a way overpowered GPU or CPU they do only to show how much whatever they're testing is capable of. They've said it many times that it's probably not necessary, but it's so that there will be as little effect as is possible from any other variables. They most likely even had that CPU with GPUs like a single HD 5570, which is clearly not necessary.

    And to be more specific, them referring to AM3r2 was within the past month or two. Before that it was very much up in the air as to what may or may not be happening. He built his a year ago, there would have been no misconstruing possible.
  5. Ok youre right by saying that they usually test in an environment where the CPU is not the bottleneck but that is the reason for my problem!

    Still I think i'll just buy that freeking card even if ill be stuck with that bottlenecking CPU.
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