New ATI Card and 6-pin PCI-e power connector

[robonave]

Hello to everybody, this is the first time I write here and is for....help!

My old video card, after months of artifacts production, is near the last breath of its life!
I was looking at HD4890/4870 video card or at the newer 5770/5750 ones which both fits my budget; the 4890/4870, from what I read around, seem to get better performances while the latter are DX11 ready and have lower power consumption.
More I have only one 6-pin PCI-E power connector on my PSU.
What is your advice on best choice? Can I use a molex to 6-pin connector adapter or am I going into troubles?
Thanks

 

[shadow187]

Hello, and welcome to TSH!

Can you tell us the brand of your PSU, as well as the wattage, and the amperage on the 12-volt rail?

*Sidenote

Remember, the drivers are quite immature for the HD5k series. In time, things will improve.

 

[robonave]

What I read on the case is WUP ATX-926 P4, the card indicates the following:
+3.3 V 30A
+5 V 55A
+12 V 28A
-12 V 0,8A
-5V 0,5A
+5VSB 2,5 A

 

[shadow187]

Yes, you should be clear to use an adapter. How much wattage does it have? It'll be a number in the hundreds, probably 550+.

 

[robonave]

It seems quite powerful 925W. What is best to connect the adapter to: the molex or something different,I have many free power connections (molex, SATA, floppy)?
Thanks for your help

 

[robonave]

I have seen 1 to 2 PCI-E power connection (but what happens to power output) or 2 molex to 1 PCI-E or 1 molex to 1 PCI-E, what is the best solution?

 

[hunter315]

I would not use an adapter on that PSU. It only has 28Amps where it counts for a graphics card, meaning that it shouldnt be rated any higher than about 400 watts. It would not be safe to run a 4870 or 4890 on that PSU. A 5750 or 5770 would be safe as they draw significantly less than the 4870, but if its an older PSU you should really consider swapping it out as they loose capacity with age.
http://www.tomshardware.com/reviews/radeon-hd-5770,2446-15.html

What are the rest of the system specs? If you have a slow CPU you wont get very good performance out of a new graphics card due to CPU bottlenecks.

 

[robonave]

The PSU is not so old (almost 1 year) like the computer. My system is:
MB ASROCK A780GXE/128M
CPU AMD Phenom quadrocore 9950
RAM 4 GB A-Data
Hitachi 500GB HD
DVD driver
But If I get 28 Amps from the +12V connector this means a 336 W available power and from the table you reference to I get a 270 W max requested power for 4890 and 253 W for 4870 why is the PSU not enough? Maybe for other users' drainage?

Just seen that there exist the possibility to install a separate PSU for the Graphic Card in a 5.25" slot (Thermaltake Power Express) what do you think about it?

 

[mactronix]

Personally i would stick with a 5770 on that PSU. If you have 2 spare Molex connectors you could try using an adaptor, but to think that you are taking a chance the PSU will run a card with older tech that requires more power to do a very similar job...Well it just dosent make sense to me.
Much better to go with new tech that you know teh PSU will power and assuming you are running Vista or later, not XP you will benefit from DX11 as well.

Mactronix

 

[hunter315]

The power tests shown there were using furmark which does not put much load on the CPU, the 9950 when at full load will put up to 140 watts, which actually doesnt leave much for the GPU, you also have to factor in the power draw of the optical and hard drives and ram.
http://extreme.outervision.com/PSUEngine
This is a pretty accurate PSU calculator, i put in your CPU, a high end motherboard, 2 sticks DDR2, 1 DVD-RW drive, and 1 sata drive and it suggests 307 watts of power. 80% of the systems power comes from the 12 volt rail so thats cutting it very close to the safe limit for your PSU, especially if it isnt well ventilated. Drawing so close to its max will shorten its lifespan.

The seperate PSUs tend not to be as good quality as a regular one, and are rather expensive for what they do. You are better off just replacing your PSU with a Corsair 550VX and not having to worry about it in the future.

 

[robonave]

So your advice is for the 4890 and a new PSU, instead of the 5750/5770 and no new PSU.
From a budget point of view 4890+new PSU cost me more than 5770 alone, do I get such better performance with the first solution to justify discarding the second one?