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How many amp to run 4890

CIT 850W Black Edition PSU 12cm Dual 12v CE PFC Model 850UB.. will this psu run my 4890
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  1. Without knowing about the CIT brand specifically, 850 watts would be enough to run any card on the market, even a dual gpu card like the 4890.

    If you check here:,2262-13.html

    you'll see it uses around 285 watts.
  2. just basing off a general ballpark guess I'd say you'd want 35A or more.
  3. sorry i know im a 'noob' when it comes to hardware, i spoke to a 'tech' who acted like he knew what he was on about.. i just want 250 fps whilst playing

    The problem i am having is my new power supply runs my 3870(how old i know - 2kidz low budjet - moaning missus) just fine, but when i plug in the 4890 it runs.. (fans go , lights flash) but my monitor acts like there is nothing connected.

    my tech friend says that the psu above only gives out 28wt on a 12v while the 4890 needs 33 wt to run... is this right? or is the problem that the card power imput plug thingies (lol- i know) are 4pin and a 6 pin, while my psu connector has 6pin and 2 pin (my3870 only needs 6pin) and then all i need to do is buy an 8pin adapter?

    i got this psu today and cba with the returns policy palava

    thanks for your previous help, and for being there for me to pick your brain :-)
  4. soory i ment to say 28amp and 33 amp :-)
  5. Best answer
    your psu has 2 +12 rails both at 28A which is effectively 56A which is plenty for the 4890 but its not to say that the psu can run at the specified power or that it may not have degraded over time.

    I suggest reseating the card or making sure it works, also trying a new psu might also work.
  6. This is a brand new cpu, so i dont think degrading is an issue, and if it doesnt run at the specified power then thats just shocking.. thanks for your reply tho, i dont have a spare psu hanging around unfortunately and my old psu is not good enough :-( will try re-seating again.

    How do i make sure it works?
  7. Best answer selected by Jkosoko.
  8. Two points.
    1) Looking at some information on that PSU, its label does not list information on maximum combined wattage. Also, it lists 230V input, not a range. These suggest to me it's a cheap PSU; I wouldn't trust it for much more than half to two thirds of its label.
    2) +12V rails are not strictly additive. The total current available in a case like this might be something like 40A, with each rail current-limited to 28A. You can pull up to 28A from either rail, as long as the total amount is no more than (in this case) 40A. This PSU doesn't list the max combined, so see #1.

    Even if overrated, this PSU should still have enough juice for a HD4890, although I certainly wouldn't try running a pair of them on it.
  9. This topic has been closed by Mousemonkey
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