1. TechSpot is dedicated to computer enthusiasts and power users. Ask a question and give support. Join the community here.
    TechSpot is dedicated to computer enthusiasts and power users.
    Ask a question and give support.
    Join the community here, it only takes a minute.
    Dismiss Notice

500W enough for HD 5770 Crossfire?

By Nushi ยท 10 replies
Aug 9, 2011
Post New Reply
  1. Hi all,

    I saw an ASUS HD 5770 for pretty cheap in an online auction place and I couldn't resist getting it since I already own one identical to it and I could use it in Crossfire. The card is in the mail, but I'm unsure about my PSU and case cooling.

    The case is an Antec Sonata III 500 (not a gaming case, I know) with a 500W power supply that came included. The power supply is an Antec, obviously, and is rated at 22A on both 12V rails.

    I have a Phenom II X4 940 BE at stock clocks, 125W TDP. Memory is 4 GB DDR2 RAM (2x2GB). In the case are also 2 3.5" SATA hard drives (both 320GB) and a BD-RE/DVD+-RW/CD-RW super combo drive.
    For cooling I have a Noctua NH-9U CPU cooler and 2 120mm case fans. One case fan blows air out of the rear between the GPU and PSU, while the other supposedly sucks air in from the front, placed between the hard drives and the GPU.

    So... will I run into any problems with this setup? I could always just upgrade our family machine with the new HD5770 since I got it so cheap. It's just that I've never had CF and am eager to try...
  2. red1776

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

    The recommendation for CF'd 5770's is a 600w PSU
  3. Nushi

    Nushi TS Rookie Topic Starter

    ok... the family computer has a 600W PSU, but switching PSUs between the two machines is quite a bit of work and there's always the risk of incompatibility. When installing the 600W thingie in the family comp to replace a broken one many years ago, I needed cutting tools and had to temporarily remove the mobo... and bend a bit of aluminum under the mobo and cover it with electrical tape to avoid shorting the mobo... all in all, a lot of work. Can't say if the new PSU or the computer case was to blame, but clearly either one wasn't up to standards...
    and I'm not sure the Antec case has a standard-sized slot for the PSU, either... so I'll probably just give it a try with the 500W PSU first...
  4. red1776

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

    The 5770 draws 110w peak, so if you keep your CPU at stock you will probably be ok if you are not running a lot of peripherals. The problem can be that OEM PSU's are almost always of very low quality and the watt/Amp rating is very often "optimistic'
  5. rockyjohns

    rockyjohns TS Rookie Posts: 80

    You are in "iffy" territory.

    The HD 5770 crossfire benchmark at JohnnyGuru (one of the most respected sites on PC power supplies and usage) states that at load the power requirement peaks at 423 watts, which is not ideal but certaily manageable in a system with no overclocking and no other components that are large power consumers. However it goes on to recommend a 600w minimum PSU If you use it in a high-end system. This is puzzling this as they also recommend a minimum of 55 amps on the 12v circuit, which is strange since 55 amps x 12v = 660 watts. To find 660w just on the 12v circuits you need at least a 750w and probably 800w PSU.


    You might also want to check out the power requirements for your existing system, both with a single and double card configuration by using the power calculator at this site. Note that it has a free "Lite" tool that calculate only the total power requirement and a subscription "Pro" tool which for a few dollars (ranging from $2 for 3 days to $10 for lifetime) will also calculate the load on the 3.3v, 5v, and 12v circuits. I recommend the Pro tool as a good investment.


    If you use the tool, let us know what you find and how it matches up, for your single card, with the one in the benchmark.
  6. rockyjohns

    rockyjohns TS Rookie Posts: 80

    I think he is explaining why the PSU manufacturers state a higher minimum power requirement than may be needed with a quality PSU.

    Your PSU is an Antec Earthwatts 500 which is a very good PSU
  7. captaincranky

    captaincranky TechSpot Addict Posts: 12,499   +2,295

    Is the "family computer" an older Dell or Compac offering. Because a buch of prebuilts had non standard prts. It's not so bad these days, "ATX standards require cross compatibility with wiring and bolt mounting pattern.! The only issue can be with very hi-watt PSUs, as they can be longer, and so intrude further into the case.

    Let's think about that for a minute. Of course it will, provided the the PSU coming in is ATX1.0 or above standard.

    Antec case mounts are ATX standard, and will work with all their PSUs, as well as everybody else's ATX PSUs.

    I suggest NOT putting the "600 watt" PSU into your soon to be crossfire machine. The 500 Watt Antec probably has at least that much punch, Although it's debatable whether it will power 2 of those cards.

    It's never a good idea to run anything at 100% duty cycle, and the card power requirement spec is set to reflect that. So, 500 watts drawn would translate to about 80% of 600 watts indicated requirements. Consequently, (I'm estimating), at full draw, the Antec 500 Watt PSU would be running at 100% duty cycle. Not a beneficial situation for heat, computer stability, or equipment life.

    The two facts you can count on are 1; the video card power requirements estimates are inflated, but 2: the available power from a PSU is NOT....!!
  8. red1776

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

    if its a Antec Earth Watts then I assume you got a barebones setup rather than an OEM machine, you would be okay in this respect. The TDP for thye 5770 is 110-115w , but that is under a Furmark like load that will not be realized unless you run...well Furmark. under heavy gaming load, the 5770 only draws a meager 70-80W. So you would be okay if you really need to CF them. I am like CC in that I just don't like to tax PSU's above 75-80% for efficiency, heat, and lifespan issues.

    Captaincranky said:
    exactly, I am going to have that put on a plaque in the shop.
  9. rockyjohns

    rockyjohns TS Rookie Posts: 80

    423w peak power system usage in the benchmark listed above divided by 500w from Antec PSU = 85%. Not ideal but definitely not at 100%.

    Nushi - would you please check on and report the model name and number of your PSU. TheEarthwatts series normally came in the Antec Sonata III, but the EA 500 PSU only has 17a per 12v circuit, not 22a.

    Nevertheless, at 34a total for 12v = 408w on 12v circuits.
  10. red1776

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

    I think you were correct the first time.
    the Antec EarthWatts EA-500D does have 22A on 12v1 and 12v2

    Learn more about the Antec EA-500D Green
    EA-500D Green
    ATX12V v2.3 / EPS12V
    Maximum Power
    80mm low noise cooling fan
    Main Connector
    +12V Rails
    PCI-Express Connector
    1 x 6-Pin, 1 x 6+2-Pin
    SATA Power Connector
    82% or higher
    80 PLUS BRONZE Certified
    Over Voltage Protection
    Input Voltage
    100 - 240 V
    Input Frequency Range
    47 - 63 Hz
    Input Current
    9A @ 100V, 4.5A @ 240V
    +3.3V@24A, +5V@24A, +12V1@22A, +12V2@22A, -12V@0.8A, +5VSB@2.5A
    UL, CUL, FCC, TUV, CE, CB, C-tick, CCC, BSMI
    3.4" x 5.9" x 5.5"
    3.6 lbs.
  11. rockyjohns

    rockyjohns TS Rookie Posts: 80

    Yes, I see the 22a. They must have increased the power. I have the Antec spec list for the EA 500 which I copied and saved when I purchased one several years ago. And it shows 17a for both 12v rails.

Similar Topics

Add New Comment

You need to be a member to leave a comment. Join thousands of tech enthusiasts and participate.
TechSpot Account You may also...