|
|
Analysis
The figures here show that the newer cards like the X1?00 & 7?00 range aren’t really using any more than the previous X?00 and 6?00 series which were used in many shuttle and low power systems. For example, if you ran a 5900 Ultra fine on your 350w PSU, then you will be fine running a 6800gt/7800GT/X800/X1800XL. The main reason is die shrinkage or more efficient architectures. In ATI's case you can see clearly that between the 9?00/X?00/X1?00 series cards there are marked drops in power consumption. This is due to a new core design and shrink from 150nm to 130nm to 110nm to 90nm. In nVidias case they've gone from 130nm with the FX series to 110nm with the 6?00 & 7800 series. That's why there's not a huge drop from 6?00 to 7800 series cards, they're both made on the same manufacturing process but with a newer presumably more efficient architecture.
Getting power to them cards!
The PCI-Express 1.0 standard allows between 60W and 75w to a graphics card through the PCI-E slot itself, without the need for an additional power connector. But with more and more graphics cards coming out that require either a Molex or 6-pin PCI-E power adapter, this is a dead give away that a PCI-E card needs more than 75W to operate stably (7800GT for example). Each 6-pin PCI-E connector can provide another 75W. So a PCI-E GFX card with a 6-pin power connector attached can draw up to 150W max, with a dual card setup they can draw up to 300W max between them both.
PCI-Express 2.0 offers a doubling of power to discrete cards, up to 150W though the motherboard.
The new 8-pin PCI-E power connector that's come out is in line with the PCI-E 2.0 standard. This means it'll provide 225W to the card with the PCI-E 1.0 slot to provide the remaining 75W for a total of 300W. This new connector is not to be confused with the EPS 8-pin motherboard power connectors already shipping with most power supplies, it's keyed differently and the polarity is reversed, so you really don't want to try and force the wrong connector in. The extra two pins are to be two extra grounding connections, but one is believed to be eventually replaced with a +12v sensor.
http://www.jonnyguru.com/forums/showthread...=171&page=2
The AGP 3.0 standard (AGP 8x) can only deliver a maximum of 41.8 W (6A from 3.3V, 2A from 5V, 1A from 12V = 41.8W and an additional 1.24W could come from the 3.3V auxiliary at 0.375A). AGP cards that need an extra power input will have a molex power connector (9800 Pro for example). By adding the four-pin Molex connections, manufacturers extended the life of AGP cards as each supplied 6.5A or 110.5W from these right angle connections (12V + 5V or 17V x 6.5A = 110.5W). Which makes a total of 151.8W available to AGP cards with a single molex connector.
Info found here http://www.tomshardware.com/2006/07/24/gra...ners/page5.html
For PCI, according to the PCI Local Bus rev 2.3, sections 4.3.4.1 and 4.4.1, "requires that an add-in card must limit its total power consumption to 25 watts (from all power rails)."
"Power Supply Rail Tolerances:
Power Rail Add-in Cards (Short and Long)
3.3 V ±0.3 V 7.6 A max. (system dependent)
5 V ± 5 % 5 A max. (system dependent)
12 V ±5% 500 mA max.
-12 V ±10% 100 mA max."
Info found here http://www.opencores.com/forums.cgi/pci/2006/02/000435
Overclocking
Many of you must be wondering how much power is drawn once overclocked. Power consumption does not change a great deal when overclocking (as seen on page 6 of the first ² link), a rough guide is to say the power consumption increases at a slightly greater rate than the overclock. So a 10% overclock will cause a ~11% increase in power and so on. In the case of volt modding the GPU, power draw raises fairly linearly with the overclock (see page 6 of the first ² link). But use this only as a rough guide, and do not count on it if you are in a small power situation such as a small form factor or very small PSU. Plus this may vary with newer architectures, but should remain fairly consistent. On the X800 Pro from the ^ article, increasing the core clock by 20MHz caused an extra 1W draw on power. With most of the other cards from that review being similar.
Multicard configurations
Due to the recent introduction of SLI and Crossfire graphics solutions I think it is time to talk a little about the power requirements of using dual video cards. By SLI/CF's very nature it would appear that the requirements on power will be doubled, as you can see by the graphs (in particular the 7800 GTX 512, X1900XT CF and X1800XT CF which I actually have raw data for) that's probably right. The X1800XT CF and GTX 512 requires slightly over double, but the newer X1900XTX CF configuration doesn't draw full (double) power. This is probably due to the fact that the XTX is coupled with an XT master card and thus gets underclocked to XT speeds. So when looking for a power supply to power these configurations make sure they can cater for a bit more (40W at least) than DOUBLE the single cards requirements (plus other PC components), this will ensure stability and allow for some overclocking head room (which I'm sure you'll be doing with these setups ;D)
Something that I've recently found regarding PSUs and the latest in top of the line mutli GFX card systems http://www.extremetech.com/article2/0,1697,1932958,00.asp A must read if your going to build a new, top end SLI/CF PC.
Recommendations
If you'd like to find out how much power (in watts) your current (pun!) PC uses at full load, the eXtreme PSU Calculator found here http://www.extreme.outervision.com/psucalculator.jsp is a good tool to help you find that out.
So now for the recommended PSU specs. For starters its recomended that you get a quality power supply, yum-cha brands often don't perform to their rated wattage. 300W PSUs may only be able to actually reliably output 250W. Antec, Silverstone, Enermax and OCZ are generally quite reliable PSU's. But there are many other brands that will do the job. There are instances of people using a 6800 Ultra with a 250w PSU. But they know what they are doing and have taken special care in the choice of hardware and monitoring, so it is not recommended. For cards drawing over 80w I suggest a 400w PSU or more, and for cards using over 100w to invest in a 480W+ PSU (while also using CPUs from around the same generation). But in SLI/CF mode with any card from the 6800/7800/X1800/X1900 series it is recommended that you power it with no less than a good quality 550w PSU. And for cards in the 6600 series it is recommended a 480w psu be used. Of course all this depends on your CPU and other components which have to share the available power, which is another section on it's own!
These recommendations take into account the usual configuration that a modern computer uses, such as multiple hard drives, dvd burners, fans, and many expansion cards and other ad-ons. So with these recommendations do not be afraid to have multiple devices.
See here http://www.slizone.com/object/slizone_build_psu.html and here http://ati.amd.com/technology/crossfire/buildyourown2.html for what PSUs nVidia and ATI certify for use with their multicard configurations. Generally something with 34 amps on the 12 volt rails. And here http://ati.amd.com/products/certified/powersupplies.html for ATI single card PSU recommendations.
原帖地址：http://forums.atomicmpc.com.au/index.php?showtopic=264 |
|
IP卡
狗仔卡
发表于 2008-9-23 12:17
QQ好友和群
收藏
分享
好贴
烂贴
提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
显身卡
楼主