Hi everyone, I own a dell Inspiron 560s with pentium dual core e6700 and an hd 5570. Anyways, on the HD 5570 it sais the minimum power supply recommended would be a 400watt PSU, but my PSU is 250w. I've been using this card for almost a year now with no problem, and I want to upgrade to the GT 640. I looked at some benchmarks online and it sais the GT 640 uses about 10 more watts than the hd 5570 on average, but the minimum psu for the GT 640 sais 350? Anyways I was wondering if the GT 640 would work on my PSU since a card that recommended 400+ watts worked on it. I'm going to use it for some light 3d modelling and maybe some gaming like Black Ops 2, etc.
Just because something seems to work doesn't mean that it should be done. I recommend getting a new PSU ASAP because that one might be close to failing considering what you're putting it through.
Also, the GT 640 is way overpriced. A Radeon 7750 can be had for about the same price (less in many cases) and is ridiculously faster while also not using much power. Also, I strongly recommend getting at least a 350w PSU and no more than a 430W PSU. Also, from a good brand such as Corsair, Antec, Seasonic, XFX, and I think that I'll go as far as to call Rosewill good too.
The reviews say that it fits in the slim Dell cases, so maybe it will fit in yours. They also say that it's okay to sue it with insufficient PSUs, so I'd take them with a grain of salt, but there's a difference between saying that something fits in a case and whether or not the PSU is good enough for it.
Maybe it will do fine on your current PSU if you underclock and undervolt it a little, but I'd be weary of that.
The GT640 only uses around 50-60w on it's own so it will work with your psu provided that there is not a lot of other things installed that wasn't already in there when you first bought the comp.
Performance wise though the GT640 is a flop, it will beat a GT240 and a GT430 but it is so starved for memory bandwidth that it's minimum fps is as bad as it gets for current generation cards. There is potential though but if the card is the common DDR3 version don't bother buying it. If it is the rare GDDR5 then buy it on the spot.
there isnt going to be a gddr5 version i believe.. we could probably see the gtx650 as being the gddr5 variant of gt640 with a higher memory and gpu overclock..could be interesting..but would still get beaten by HD7770.. nvdia is terrible in budget cards segment. lol
not to mention its very unsafe to run gt640 on 250W psu..