4850 / 4870 Crossfire PSU requirements

[!TIMMY!]

I am thinking of upgrading to a 1gb 4850 / 4870 and ocing it (because I game at 1920 x 1200) and I want to go Crossfire later on (DFI X48 LT).

Do you think my PSU would be able to handle these cards in crossfire? OC3D Review:

http://www.overclock3d.net/reviews.php?/power_supply/silver_power_blue_lightning_600w_psu/1

On the ATI site, it states that a minimum of a 550w for 4850 crossfire and 600w for a 4870 crossfire (which seems low to me).

What do you guys think? My PC is oced (see sig) and I have 5 HD's, 2 optical drives, a sound card, a NIC and 7 fans in there.

 

[JN]

Yeah I think it should be fine mate. I cant quite remember much about that PSU now but you may find its a bit more noisy as it will be running closer to to its max output and running hotter.

 

[!TIMMY!]

Cheers for the reply Jim, so you think it could handle 2 4870 1gb oced?

 

[JN]

Cheers for the reply Jim, so you think it could handle 2 4870 1gb oced?

Yeah should be fine mate. I don't know the exact measurements for those cards but even if they pulled 120w each @ load, that would still leave you with approx 200w left on the +12v rails for the rest of your system.

 

[GavX]

It can't power 2 4870's, only has 2 PCI-e power doo-dahs, unless you want to get molex ones into the equation

 

[JN]

It can't power 2 4870's, only has 2 PCI-e power doo-dahs, unless you want to get molex ones into the equation

Yeah unless ur fussy about looks the molex converters will do the job tbh. Shame to bin a perfectly capable PSU due to lack of connectors.

or do what I did and connect the two pci-e plugs together on the back of the card using your soldering skills

 

[GavX]

Can you get away with that? (On both accounts...)?

My solder-fu is weak, but in time I hope it to grow strong, and save me £100 on a new PSU if you can do this...

 

[!TIMMY!]

My soldering skills don't exist, so it will be molex converters for me when I get the 2nd card. Just now got to save up 4 the 1st 4870 1gb a new HD and sata card.

 

[JN]

Can you get away with that? (On both accounts...)?

My solder-fu is weak, but in time I hope it to grow strong, and save me £100 on a new PSU if you can do this...

You can indeed. I actually had a 4870 with the two PCI-E connectors joined together with solder and two capacitors missing from the PCB - still worked perfectly lol.

 

[Rastalovich]

Yeah I think it should be fine mate. I cant quite remember much about that PSU now but you may find its a bit more noisy as it will be running closer to to its max output and running hotter.

U got the equipment in-place there to put a full rig together, with perhaps a 1kw psu - run the whole thing at 100% (oc, cpu, gpu, write to all drives/opticals) and record how much of that psu gets used ?

 

[JN]

U got the equipment in-place there to put a full rig together, with perhaps a 1kw psu - run the whole thing at 100% (oc, cpu, gpu, write to all drives/opticals) and record how much of that psu gets used ?

Yeah I've got pretty much everything i'd need tbh. In fact IDNet asked me the other day how much power our new server would be drawing.

Bearing in mind that its got 12GB ram, i7 965 OC'd to 4GHZ, 4x SAS Hard disks, RAID Card, 4 NIC's....it used 200w.

 

[Rastalovich]

It's tricky also in that there's a burst of requirement at a startup from cold, iirc, then the level it semi-idles at, then the biggest possible where u try to run everything possible of running at the same time.

Just be an interesting adventure imo to build a theoretically massively power hungry gaming system and see how much it really needs.

 

[JN]

It's tricky also in that there's a burst of requirement at a startup from cold, iirc, then the level it semi-idles at, then the biggest possible where u try to run everything possible of running at the same time.

Yeah very true. Most of that seems to come from the hard disks which can use anything up to double the amount of power they normally would. This is where the 'peak' power of a PSU comes in handy. I've had units here rated at 800w which are capable of up to 950w for a few seconds before OCP kicks in and turns them off.

Just be an interesting adventure imo to build a theoretically massively power hungry gaming system and see how much it really needs.

I think there's a certain amount of education that would need to go along with that as well. For example you could build the most beastly rig and find out that it only pulls 650w at load, but to go and tell people that a 700w PSU would be more than enough to power a monster system would be far from the truth.

Things like rail layout (a 700w PSU with 6x +12v rails rated at 10a each is just asking for trouble), efficiency curves, and noise levels of a PSU running at almost full capacity also need to be considered.

 

[Ham]

Wont that just boil down to making sure you buy/use/install a quality PSU? And the best way to go about that being (unfortunatly) brand snobary.

Another figure just to throw out there, benching around 4.8ghz @ 1.9ishV on a dual core + 8800GT never pulled more than about 170-80w. Was using more than that to cool it...

Edit: And we've driffted rather for OT here, better nudge it back on the rails.

Tim, if you need any adapters made, gimme a shout .

 

[!TIMMY!]

Will do cheers Ham