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Two graphics cards vs one

By Bob Sawyer · 15 replies
Jan 8, 2012
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  1. Hi guys

    I posted a few weeks ago re upgrading my old Ge Force 6800 to something a bit more up to date, but have since decided I'd be better to go the whole hog and get a new rig.

    I'm looking at a choice between the following:

    Dual nVidia GTX 550 Ti 1GB PCI Express Graphics Card
    ATI HD6870 1GB PCI Express Graphics Card

    I gather the dual nvidias would be faster than the individual ATI, but would it be a marked increase? (I'm looking at the moment to play Skyrim at a decent rate, but obviously there's the future to consider).

    I've not had a system with 2 gpus before - is there anything I need to be aware of or is it basically the same as having 1 card to the end user?

    Any advice much appreciated!
  2. cliffordcooley

    cliffordcooley TS Guardian Fighter Posts: 9,171   +3,263

    Connecting two nVidia SLI or two ATI Crossfire cards together would practically double your performance while connecting them together as if they were one card. There are issues that can arise from SLI or Crossfire (I have only read about the issues), so if possible it might be best to get the performance you need from one card.

    If you are thinking about SLI or Crossfire for a future upgrade, you might consider changing the 550Ti to 560/560Ti. The 560/560Ti closer matches performance of the HD 6870.

    I've not had a SLI or Crossfire system either so consider my post as opinion based on what I have read over the last two years. Even though not completely accurate, I base allot of performance levels from PassMark - G3D Mark. The reason for the inaccuracy is mostly from the scores being influenced by Over-Clockers. The benchmarks do give a general guideline for performance.
  3. Bob Sawyer

    Bob Sawyer TS Rookie Topic Starter

    Thanks for the advice.

    The dual card option is pushing my budget a bit, so I think I'll stick to the 1 card route if there are possible issues as well.

  4. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,223   +163

    A dual GTX 550 Ti will give you performance right around a GTX 570 and be a sizable bump from a HD 6870. SLI and CF problems are not prevalent these days. I work with them very frequently and would certainly not rule out a dual GPU machine because of 'anticipated, or inherent problems' You will run into a "Skyrim" cf profile wait occasionally, but that is the exception, not the rule. The biggest consideration is making sure you have adequate PSU backing a multi-GPU system.
  5. fimbles

    fimbles TS Evangelist Posts: 1,171   +203

    Sli is pretty transparent to the end user these days, And as said in previous posts will double your frame rate in most new games.

    Make sure your psu is up to the job.
  6. slh28

    slh28 TechSpot Paladin Posts: 1,706   +172

    This is an obvious point but hasn't been mentioned yet... is your motherboard actually SLI/CF compatible? Considering you're coming from that 6800 that would indicate quite an old build.
  7. LNCPapa

    LNCPapa TS Special Forces Posts: 4,247   +448

  8. Bob Sawyer

    Bob Sawyer TS Rookie Topic Starter

    Sorry for late reply guys.

    That sounds pretty good to me! - I'm now definitely back to the 2 cards route.

    Would a 600W PSU be OK? - I'm sure motherboard will do the job.

    Thanks for all the help so far!
  9. dividebyzero

    dividebyzero trainee n00b Posts: 4,891   +1,262

    The 600w depends on the quality of the PSU. 600w should work out at a little under 50A on the +12v rail(s). if you're close to that number then you should be good to go (Tweaktown recorded 437w with two overclocked cards and an Intel 980X CPU- which isn't noted for it's power frugality).
    Peak gaming power draw for a GTX 550ti is ~112w per card (TDP is 116w). You could get that figure to 135-140w with some overclocking and a burn in/torture test.

    If you're in any doubt whether the PSU can handle the load long-term then post it's model number and I'm sure people here will dissect it's ability...or lack of.
  10. Bob Sawyer

    Bob Sawyer TS Rookie Topic Starter

    Wow - too technical for me!

    The model is:

    Quiet Xilence 600W 2 x PCI-E 135mm Fan

    Up to the job do you think?
  11. dividebyzero

    dividebyzero trainee n00b Posts: 4,891   +1,262

    If this is your power supply then it's borderline at best. The specifications are more in line with a 500w unit....less, if the power supply is more than three-years-old (power supplies degrade over time and use).
    If you aren't planning on upgrading the power supply, then a single graphics card is probably the way to go.
  12. red1776

    red1776 Omnipotent Ruler of the Universe Posts: 5,223   +163

    1) semi-fan-less
    2) Fan does not kick in until it hits it's limit of 85c
    3) This does not happen until "most of it's 600w is being utilized"
    4) 24 mo warranty


    How much you want to bet that fan kicks in when only using a single card?!

  13. Bob Sawyer

    Bob Sawyer TS Rookie Topic Starter

    Eeek! Bullet dodged there then - thanks.

    I do want to get 2 cards now, so I need to sort another PSU.

    The outfit I'm buying from have suggested I might get some sort of free upgrade if I place an order in the next week or so (I'm getting them to build the lot for me).

    I thought I might try and talk them into this one which they do:

    antec modular 750w psu dual 12v rail

    Link: http://www.scan.co.uk/products/750w-psu-antec-true-power-new-750-modular-82-eff-80-plus-bronze-sli-crossfire-eps-12v-quiet-fan-atx-

    Would this be suitable? (I'm afraid I just don't understand PSUs at all).
  14. slh28

    slh28 TechSpot Paladin Posts: 1,706   +172

    Yes, that's a good PSU.
  15. dividebyzero

    dividebyzero trainee n00b Posts: 4,891   +1,262

    If the Antec unit is free, then why not....it's certainly a big upgrade to the unit you presently have. For about the same money, Corsair's TX650M is probably the better deal. Even though it's rated as a lower wattage it is a more powerful unit. It's also backed by a five year warranty (the Antec is 2 years).
  16. Bob Sawyer

    Bob Sawyer TS Rookie Topic Starter

    Thanks for the advice - I'll have to see how my negotiating skills are now...

    That's useful to know. They also do the 600W Corsair, so if they won't let me have the have the 750W antec I'll see if I can get this one instead. Unfortunately they don't list the 650W, but maybe they have one knocking about if I ask nicely and say it's just the PSU that's holding me back :)

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