Elliot B. Posted December 24, 2013 Share Posted December 24, 2013 I have a Asrock H77M motherboard and a 7870 XT Tahiti-based video card. My motherboard supports CrossFireX, so I was going to buy a second Tahiti-based video card. The website for my motherboard states: 1 x PCI Express 3.0 x16 slot (PCIE1: x16 mode) 1 x PCI Express 2.0 x16 slot (PCIE2: x4 mode) 2 x PCI slots Supports AMD Quad CrossFireX? and CrossFireX? Since the second PCI Express slot is slower than the first slow, will this slow down the second card?Or - is my motherboard fine to use CrossFireX? EDIT: The card I have in there covers two slots. I hope it's not covering the second PCI Express slot :/ Link to comment Share on other sites More sharing options...
mattmatik Posted December 24, 2013 Share Posted December 24, 2013 From the picture, looks like your second PCIe slot for a graphics card is at the bottom. So if you put another card in there I believe they will both go to 4x/4x. Not sure what difference this makes, really. My mobo goes to 8x/8x for SLI - think you'd need a pretty beefy mobo to have 2 16x 3.0 slots anyway. Link to comment Share on other sites More sharing options...
Phouchg Posted December 24, 2013 Share Posted December 24, 2013 You can do it, but it will hamper performance. According to Tom's Hardware - about 10-20%. http://www.tomshardware.co.uk/pci-express-scaling-p67-chipset-gaming-performance,review-32164-10.html Also, ensure that there's proper airflow especially for the uppermost card and that you have the necessary power they require to begin with. Link to comment Share on other sites More sharing options...
Elliot B. Posted December 24, 2013 Author Share Posted December 24, 2013 You can do it, but it will hamper performance. According to Tom's Hardware - about 10-20%. http://www.tomshardware.co.uk/pci-express-scaling-p67-chipset-gaming-performance,review-32164-10.html Also, ensure that there's proper airflow especially for the uppermost card and that you have the necessary power they require to begin with. That article is almost 3 years old. I wonder if things have improved since. Link to comment Share on other sites More sharing options...
+PeterUK MVC Posted December 24, 2013 MVC Share Posted December 24, 2013 That article is almost 3 years old. I wonder if things have improved since. How old is your Asrock H77M? primexx 1 Share Link to comment Share on other sites More sharing options...
Elliot B. Posted December 24, 2013 Author Share Posted December 24, 2013 How old is your Asrock H77M? Amazon UK says the motherboard was first available 11 April 2012. Link to comment Share on other sites More sharing options...
snaphat (Myles Landwehr) Member Posted December 24, 2013 Member Share Posted December 24, 2013 I see no reason why the situation would have changed drastically. The age of his motherboard and the chipset aren't really the problem here. It'd be a driver issue if anything. The industry has probably largely moved on with PCI-E 3.0 and there probably hasn't been a large effort to improve the situation with x16/4x setup. Link to comment Share on other sites More sharing options...
Snake89 Posted December 24, 2013 Share Posted December 24, 2013 the graphic cards will only running at PCIe 2.0 x4 speeds. kinda making it useless to run crossfire with a 7870. Link to comment Share on other sites More sharing options...
Elliot B. Posted December 24, 2013 Author Share Posted December 24, 2013 ok cheers, guys :) I'll try and find the cheapest motherboard that supports 2x x16. Link to comment Share on other sites More sharing options...
+PeterUK MVC Posted December 24, 2013 MVC Share Posted December 24, 2013 A newer chipset like H77 vs H57 has not really changed for the PCI-E that it runs off the only reason H77 has PCI-e 3.0 is because thats run off the CPU for one slot instead of running two slots from the CPU and running x8 by x8 without running a x4 slot from the chipset. So not much has changed as motherboard makers are doing this limiting for you to of gotten a better board if you want the most out of CrossFireX setup. Link to comment Share on other sites More sharing options...
+PeterUK MVC Posted December 24, 2013 MVC Share Posted December 24, 2013 I'll try and find the cheapest motherboard that supports 2x x16. With your Core i5-3570K you can only run PCI-e 3.0 x8 by x8. Link to comment Share on other sites More sharing options...
Elliot B. Posted December 24, 2013 Author Share Posted December 24, 2013 With your Core i5-3570K you can only run PCI-e 3.0 x8 by x8.Oh. This is all so confusing :( I thought the 3570K was meant to be an excellent CPU?Would 2x x8 GPUs even be much better than 1x x16 GPU? Link to comment Share on other sites More sharing options...
+PeterUK MVC Posted December 24, 2013 MVC Share Posted December 24, 2013 With the bandwidth PCI-e 3.0 has running a card at x8 is more then enough. Link to comment Share on other sites More sharing options...
snaphat (Myles Landwehr) Member Posted December 24, 2013 Member Share Posted December 24, 2013 Oh. This is all so confusing :( I thought the 3570K was meant to be an excellent CPU? Would 2x x8 GPUs even be much better than 1x x16 GPU? I would imagine so. Single cards do not saturate the 16x lanes last I checked. IIRC, there was little difference in using a 16x vs 8x lane in practice for a single card. *Disclaimer: I didn't check the state of recently. EDIT: I just googled briefly, and I'm not seeing anything to indicate otherwise than I just said, so I would surmise that you are good to go with a dual 8x/8x solution. Link to comment Share on other sites More sharing options...
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