How does 4870x2 act?

[Moosemans]

Hi, i tried google this but idk what to google heh.

How does the 4870x2 act ? does it act like 2 4870 CF or does it act like 1 card?
If i run an older game that does not support Crossfire will that game perform better on the 4870x2 then a single 4870?
What about the 4870 in CF does it only use one card in older games?

[DMB2000uk]

I think the OS sees it as one card, but catalyst control center sees it as a crossfired pair.

If time has been spent to code the drivers of old games, then the 4870x2 should 'fail' gracefully and performance will be equal to just one 4870 when crossfire isn't supported.
However in older games that don't support crossfire, it is possible for the card to actually have performance that is worse than just one card.

I'm not sure how many games actually show this negative performance problem, but you might actually be able to disable crossfire in the CCC, and just run the game on one core.

I don't know anything for fact with this, so unless someone that knows otherwise wants to come along and correct me, it's my best understanding.

Dan

[IRQ Conflict]

"you might actually be able to disable crossfire in the CCC, and just run the game on one core" Yes, this should be possible by disabling 'Catalyst AI'. I don't have an X2 though so you should verify it with someone who has.

[Moosemans]

so what ur saying is that the 4870x2 in some cases might perform worse than a single 4870? i dont quite get that, i mean isn't it basically 2 4870's fused toghether ?

[DMB2000uk]

It'd do the same thing if it were two 4870's in crossfire. It's some kind of crossfire bug in general, rather than anything specifically wrong with the 4870X2.

Dan

[Moosemans]

Ok, well im thinking of getting a 4870x2 and sell my single 4870, i have a 650watt psu so i rather run a single 4870x2 then 2 4870 CF not that i cant do CF but the 4870x2 takes less space + it wont get as hot. One more thing, will my q9450 stock speed bottleneck a single 4870x2?

[IRQ Conflict]

Not likely my friend. Even an OC'ed Q6600 will be enough. See this.


Edit: You may want to consider an upgrade on your PSU. How many amps does yours provide? iirc My X1950's need 38amp and I'm not sure what an X2 requires. The PC P&C Silencer 750 Quad I use provides 60 amps on the 12v rail for example. Just something to keep in mind.

[Moosemans]

http://www.fractal-design.com/?view=pro ... =3&prod=10

thats my psu, its a good quality one.

[IRQ Conflict]

Ok, the sticker reads 20 amps on the 12 volt rails. So I would be suspect if it is going to be enough. I think the X2 needs ~40 amps. You can try it, but if your system reboots under load you may need to upgrade to a more powerful PSU.

[DMB2000uk]

The 40amps is meant as a system wide rating, so it's not just the card.

But, if you make sure that the motherboard is powered with a specific 12v rail, then plug the 6pin from a second 12v rail to the 4870X2, and the 8pin from a third 12v rail again to the 4870X2, you should be more than fine in regards to power. Odds are that the PCIe rails and motherboard 24pin and 8pin are separate anyway, so you shouldn't have to even worry about separating those.

Dan

[IRQ Conflict]

That's true, it will depend on the particular PSU. I've heard of people running on as little as 600w and others that run 600-650w but their PSU's still weren't up to the challenge. I still think 20 amps is pushing it though, maybe not. I couldn't find any decent info on the cards actual amperage draw.

Edit: I haven't done the math myself as I am unaware of the cards total voltages under load or at idle, however I did find a post over at AMD's forum that seems to click.

Wattage is volts x amps

If you have less amps, then you have less watts.

12 volts x 40 amps = 480 watts

The thing with the PSU is that you need a quality one that can put out that amount of amperage consistantly.

The only way you keep 480 watts, and have less amperage, is if the voltage goes up...

Since the voltage CAN'T go up, your amperage has to drop, meaning your wattage goes down.

As your PSU gets hotter, it will start putting out less power.

By the numbers you supplied, the X2 consumes 57 watts more at full load than at idle... 4.75 amps more than idle.

Budget on .7 amps per HD on the 12 volt line when not doing anything... That'll give you a bit of breathing room... If you only have one or two HD's you don't have to worry about it...

The total wattage rating of a PSU is something you use to get a rough estimate... What you need to pay attention to is the AMPS on each rail.

A 750W PSU can only have 30 AMPS total for all the + 12 volt outputs it has... But it can have massive 3.3/5.0 power.

If you have a multi-rail PSU you want at least 35 - 40 AMPS per rail.

That will give you 420 - 480 watts per 12 volt rail.

Link.

[Moosemans]

lol not even a frickin 650watt psu for like 140$ isn't enough, then i dont want to know what u need for 4870x2 is CF. Im not going to buy the card if there are people in this thread that doubt it will work.

Thanks for all answers though

[IRQ Conflict]

I don't mean to discourage you Moosemans. I'm just trying to warn you that some have had problems running a low amperage PSU with some set ups. Yours might be fine. By the way, the PC P&C Silencer 750 is only $104.99 CDN. After the rebate.

[DMB2000uk]

I don't mean to discourage you Moosemans. I'm just trying to warn you that some have had problems running a low amperage PSU with some set ups. Yours might be fine. By the way, the PC P&C Silencer 750 is only $104.99 CDN. After the rebate.

I agree that cheaper 650W rated PSU's would have problems with running a 4870X2, but I think this PSU will be able to cut it.

I've not really heard much of fractal designs myself, but they seem to make a big deal of pointing out that the power ratings are continuous outputs and not peak ratings on their PSUs. Based on the total wattage available on the 12v rails, gives us 50A on the 12v lines. Another thing that makes me think Fractal might be an alright PSU maker is the fact that they tell you which rails are which on the modular connectors, so you can make sure you are balancing the load properly.

Just make sure the 4870X2 has the three 12v lines going in (like I suggested in my other post) and I really think you'll be alright.

Dan

[Moosemans]

cool, well the 4870x2 needs at least 650watt psu for it to work it says. Nothing in my computer is OC'd and if it wont work, i can turn it back to the store.

My current single 4870 is Asus hd4870 1gb and i have two 6 pin power cables connected to it*, can i connect them in the 4870x2 if i get it.? or does it have to be one 6pin and one 8 pin?

*both my cables have 8 pin which u can put aside 2 pin to make it 6

http://www.mysimon.com/9024-3055_8-33140361.html 625watt
http://www.pcsilent.de/en-pd-be-quiet-p ... -1012.html 600watt

take a look at those links, its psu's which i found on HIS homepage for
Power Supplies Certified for Single Card Operation , those could handle a 4870x2

[Rutgar]

Just make sure the 4870X2 has the three 12v lines going in (like I suggested in my other post) and I really think you'll be alright.

Dan

Can you clarify what you mean by "three 12v lines" going in? You mean on the card(s) themselves? I bought two 4870 X2's. Each has two power connectors. One 6 pin and One 8 pin.