Single ATI Mobility Radeon HD 4870 to a duel HD 4870(crossfire)?

Hello Gentlemen (and Ladies if applicable) I (hardware noob) have a question I'd hope could be answered here: (I used the search feature before this post but could not find anything relevant)

I bought my M17x back in February of this year (2010) and went with the Single ATI Mobility Radeon HD 4870. Now, a few months later I regret being cheap and not going with two of them. It runs most of my games just fine at max setting. However, some of the newer games (such as Assassins Creed II and Star craft II) run at about 20-35fps on the medium settings. Which is good, I know, but I'd like a little more power behind it

So my question, after you now know my life story, is: How do I go about upgrading to duel 4870's?

Can I just get another 4870 card and the crossfire stuff and connect them? Do I have to get 2 new cards with the crossfire (if the one i have is not compatible with crossfire)? Is there another alternative (like 2 new different, newer cards)?

Thank you in advance for your answers and help, and I apologize for my clueless-ness and if this has been posted before and I missed it.

 

Regardless of the route you choose, if picking up a second card or a pair of cards, be sure to confirm (a simple call to tech support will work) your PSU is the correct PSU. I believe when systems are shipped with 1 GPU, the PSU needs to be changed out when going to dual GPU.

 

BatBoy is right. Generally if you order one GPU or a none extreme CPU you get a 150W adaptor. When you upgrade your can just get the card and the crossfire cable and it should work. But don't forget that your also going to have to get a fan and a heatsink to accompany the extra card. It's your decision on how you want to go about it. But as of now your shopping list should include

4870 GPU
Crossfire cable
Heat sink
Fan
250W PSU
Thermal Pads for the memory
Thermal paste for the GPU core.

I'd start by calling Dell and seeing what they offer as far as price goes and if they can have a tech install it. If you purchase from Dell and have them install it, it is covered under your current warranty.

 

thermal pads..... still have no clue where to get? or what to get?
No, you don't have to buy two new cards, just the secondary.
Yes, the 240W adapter is nescessary, but the HSF and Xf Cable are included in the price for the secondary gpu, and they should be cheaper now. Last time I checked I was quoted $400,(3 months ago) and the rep said to wait till around this time for a price drop. I went against the grain... instead of AS5 I got Tuniq-TX3 thermal paste my lowest temps are 38-40, and max temps 58-60 sometimes a little higher.

And there are newer ones out the 5870's which you can XF, but thats gonna be almost a $1k dollar deal where as the secondary 4870 would be like maybe $2-300.(maybe if the rep was right)

 

Hey guys, Thank you for all the info and help, I did a bit of research and it turns out i have a 240w psu, must be because I have the turbo version of the i7 620m...?

So then that means I just need another 4780, the xfire cables (although Mkelliny said it comes included if I understood correctly?) and a fan. Good start I guess, thanks again guys, but as always, anymore additional info you might want to throw in is highly appreciated

 

Yes, the XF cable & HSF(Heatsink/Fan) are included when buying a secondary GPU, and to make sure that you have the right PSU I have a
Flextronics PA-9E
P/N: J938H
Model No: GA 240PE1-00
the input is ~100-240V
the Dell P/N what is on the white sticker should be something like this 0J938H

I know there is another one I think its brand is Delta? not Sure. You most likely have the 150W(they don't ship out the 240W with the i7-620M, 720/820QM), but if you have what I listed above then you have a flextronics 240W adapter like me.