Power Supply Recommendations - ATI X1950 512mb AGP???

[Potoroo]

Potoroo; Your reply has actually got me a bit interested. I did the test in alalou's post and put in all my hardware i have (Included the X1950 as that is what it will be eventually) and it says that i needed a PSU of at least 320W. Now since i have a 350W supply now does this mean that i 'should' be able to use this card fine with my current setup?

Also on a side note does anyone know what any of the data on the side of the PSU refers to? I read above about the different rails but obviously i haven't a clue on my current PSUs stats as it was in the case when my mum got it 2 years ago when putting this PC together (And i can't find any information on the net either). Attached a picture below to show what it says;

Rabid is quite right to point out that the PSU's nominal total wattage is inadequate as a guide to its real capacity. PSUs provide 12v, 5v and 3.3v rails. It used to be that 5v was most important. However, as more devices have become 12v today the 12v capacity has become most important. Get that right and the 5v and 3.3v capacities pretty much fall into place.

The data on the image you provided shows clearly that yours is an older PSU. The key number is the +12v capacity. It has a single 12A rail. That's a nominal 144W (12v * 12A = 144W). Ignore the -12v rating as that's only provided for backward compatibility with some (very) old motherboards. It hasn't been used in contemporary motherboards for years.

So, lets make some educated guesses about how much power you'll really need. You haven't specified your CPU but your motherboard is Socket 754, so assume an Athlon64 3700+. Its thermal capacity is 89W, so if we assume a DC conversion efficiency of 90% we can calculate:

(89W/12v)*(1/0.9)=6.7A

A spinning HD consumes around 1A and a DVD-ROM around 1.5A. Add 0.5A for a fan or two and you've got 3A. All up that's 10A. (Ignore the HD spin-up consumption of around 3A since at that time the video card is in 2D mode which consumes vastly less power than 3D mode).

So far, so good.

Now, your video bus is AGP. Older graphics cards draw all their power from the AGP bus, which can supply a maximum of 41.8W (6A @3.3V + 2A @5V + 1A @12V). However, cards like the X1950 Pro AGP are essentially just the PCIe version with a PCIe-AGP bridge chip, so they need extra 12v which they get from either one or two supplementary power connectors directly from the PSU. This is usually the 6-pin PCIe connector, although on some older cards it may be either one or two 4-pin Molex connectors (the Molex connectors are the same ones that you use to connect power to things like hard disks). I believe the X1950 Pro AGP uses 2 Molex connectors but check with your vendor first.

Xbitlabs measured the PCIe X1950 Pro peaking at 65.7W (5.8A). Other sites have higher results but as far as I'm concerned Xbitlabs is the only hardware review site that measures video card power consumption properly. They put shunts into the bus itself and the supplementary power connector if necessary so they measure exactly what the card is drawing. It will be close enough to the AGP power consumption figure to be useful, hence:

10A + 5.8A = 15.8A.

There you have it. These estimates are close enough to tell you you need a new PSU with more 12v capacity. Even if it was something like 11.9A you'd still want to upgrade.

Right this one looks reasonable http://www.antec.com/uk/productDetails.php?ProdID=07656 and found it on the net for £60 (Well if i need to replace it i might as well get something that is goof).

Lets check out the specs for the TruePower Trio 550. It has three +12v rails, each with a nominal capacity of 18A (3*18=54A). However, note the fine print. The total real 12v capacity is 504W (42A). 54A - 42A is a big difference but an important one. You never achieve the total nominal capacity across multiple rails, so unlike many manufacturers Antec are being honest about the real 12v capacity. 42A is still so far beyond what you need it's not funny but if having that much headroom will help you sleep better at night then go for it.

Another thing I like about Antec is they quote their efficiency ratings at 50C. Since PSUs become less efficient as they get hotter most manufacturers quote their efficiency ratings at 40C. Yes, I like Antec. I've used them myself and the NeoHE is my PSU of choice (I like modular PSUs because they help make cabling easier). But equally, there are other decent PSU manufacturers out there. Just not no-names that claim to provide 600W for less than 20 quid.

1 slight problem though ... Can anyone confirm whether this will work with mothorborads that have a 20-pin ATXPWR1 + ATX12V1 connections? This isn't really answered anywhere that i have looked and obvioulsy don't want to spend £60 for it not to be compatible.

It will be fine. If your motherboard has only the 20-pin connector then physically split the 20+4 connector from the PSU in two (it's trivial, you can do it with your fingers), use the 20-pin and just leave the 4-pin dangling. If it's one of those that won't split then just plug in the 20 pins and leave the extra 4 hanging over the end.

[PrinceGaz]

Another thing I like about Antec is they quote their efficiency ratings at 50C. Since PSUs become less efficient as they get hotter most manufacturers quote their efficiency ratings at 40C. Yes, I like Antec. I've used them myself and the NeoHE is my PSU of choice (I like modular PSUs because they help make cabling easier). But equally, there are other decent PSU manufacturers out there. Just not no-names that claim to provide 600W for less than 20 quid.

Antec have had there ups and downs in recent years. They've never been a bad PSU manufacturer, but at times they have only just qualified as a good one (certain Antec PSUs are not as good as you might expect). They are better than the vast majority out there of course.

I've got an Antec TP II which seems to be doing a decent job at powering my machine (I say decent because there is an unconfirmed issue with those Antec PSUs and DFI motherboards, possibly related to standby voltage, which requires the PSU is turned on for at least a full minute before the motherboard can cold-boot).

Modular PSUs are a mixed-blessing. Yes it makes cabling easier as you don't have any unnecessary cables running from the PSU, but they make for an inferior PSU as every cable connection (especially high amperage connections like those at the sockets of a modular PSU) incur a voltage drop. It is not a great drop, but it is a drop nontheless, and one which can be avoided by using a conventional PSU with all the wires permanently attached, and the ones not needed stuffed out the way behind or between other parts. It isn't difficult to stuff all the left over cables into an area which needs no airflow, that's all part of putting together your own PC. The voltage-drop from modular PSUs won't matter to most people, but if you want to push things to the limit (overclock it) they are best avoided.

One thing I can say for certain is the no-name unbranded PSUs rated at 450W or 550W which are sold very cheaply in high-street or internet stores, are almost invariably junk. With PSUs you generally get what you pay for, and brand names like Antec, Enermax, OCZ are a much better choice than some unspecified manufacturer PSU with even twice the wattage.

[Potoroo]

Voltage drop due to the increased resistance from the modular connectors is way overstated by the PSU manufacturers trying to sell you ridiculously over-powered PSUs. I have put NeoHEs in every box I've built in the past two years, including my own. Some are overclocked (including mine), some aren't. Everyone of them runs well within the ATX margin for error for voltages. I regard the NeoHe range, for example, as superior to the True Powers, despite the latter having dedicated cabling. TP IIs have a bad reputation for unreliability under heavy load. I'm less certain about the TP IIIs. I assume Antec have improved them.

[jennings]

Essntially items that i have that will mainly be in use are;

AMD Sempron 2800+ Processor
CRRW Drive
DVDRW Drive
Soundcard (5.1 surround sound)
Roughly 6 USB ports (But this does vary - 6 is the maximum though)
X1950 Graphics card
SCSI 7200 RPM hard disk
1 fan
2GB DDR400 RAM

And thats basically it - So its not really going for a 550W model for the extra 1A (Cost wise its about £8 more which is hardly anything to be honest) that is gained on the various channels. I'm still not decided between the modular Antec one or the truepower Antec one. The idea of only having pulgged in whats required is swinigng me that way as in my PC tower now i have a huge mass of cables that are not used for anything.

... And yes my budget of £40 has gone out the window. Might as well replace this once so will get a decent one that will last the next 2 years.

Many thanks for all the very good advice - Its really been very helpful

[dee4141]

I've been reading this thread with interest as I'm considering upgrading to an x1950pro (pci-express) but have only a 300watt PSU. I have a SFF Antec NSK1300 cube-type case which has an Antec proprietary PSU included. I built this last year and the system is currently an AMD AM2 4200x2 + 1GB DDR2 + X1300pro. The system runs sweetly at around 50 Degrees C and plays MSTS and Oblivion quite well.

Using a PSU calculator it appears that this system currently requires 170Watts, but upgrading to the x1950pro would increase the requirement to 200Watts. Do you think this is a viable upgrade or would it be asking too much of the PSU? Would appreciate any comments, Thanks.

[Potoroo]

Stop thinking in terms of nominal total wattage and start thinking in terms of real 12v capacity. Knowing nothing about your Antec proprietary PSU there is no way to make any reasonable comment either way.

[dee4141]

thinking in terms of real 12v capacity.

PSU states : +5v 26A, +12v 18A, +3.3v 27A

+5v, +3.3v max output 195w

[PrinceGaz]

Whilst I will be the first to advise buying a quality PSU, the actual wattage used by a typical PC is much less than many people think.

To put things in perspective, here is a summary of my PC:

Athlon 64 X2 4400+ overclocked to 2.5GHz (5000+ equivalent) with slight over-volting
2GB DDR400 memory
GeForce 8800GTS 640MB overclocked by 20% in all three areas (core, shaders, memory)
2x 7200rpm 3 1/2" hard-drives
DVD-RW drive
CD-RW drive
4x 80mm case-fans
plus other odds and sods like an Audigy 2ZS soundcard but they take very little power

When idling, my PC takes about 195W from the wall (this is with a power-monitor thingy from Maplins, which they regualrly sell for £15 in their sales). Given that even the best PSUs are only about 80% efficient, that means my PC is actually drawing less than 160W of power from the PSU when it is idling.

When both cores of the CPU are fully stressed (using something like Prime95 twice), the power drawn from the socket increases to about 280W. Fully loading my 8800GTS graphics-card as well (with the Rthdribl benchmark) can increase that to 335W.

That 335W is somewhat more than my PC draws under any normal conditions, it is only the combinations of those demanding stress-tests that can push it that high. Assuming an 80% PSU efficiency, that would mean the components in my PC under those conditions were drawing about 270W in total- the other 65W being wasted by the PSU itself.

For comparison, playing MSTS or EARS with the graphics settings set as high as my 8800GTS can manage results in a load of 285W or so. Neither MSTS or EARS makes any real use of the second CPU core though, which explains some of the 50W lower usage while playing them. The remainder is explained by the fact that the combination of tests I ran pushed both the CPU and GPU to their limit, beyond which any game normally does.

The thing is, a box like mine is only drawing 335W from the wall under maximum load conditions, meaning the PSU is only having to deliver about 270W. It makes a mockery of the 550W requirements some people throw around, especially as the 8800GTS is quite a power-hungry card (like the high-end X1950's). Now I would never recommend running a PSU close to its limit, such as a 350W for my system which may draw in excess of 270W for instance, but a good 450W PSU would certainly be fine.

The emphasis is, as always, on the "good" as you can get cheap 550W PSUs which would be unreliable and could cause random crashes when powering my box, but a good 430W PSU would keep it running steadily throughout.

[CaptainBazza]

You can read PSU specs with the same credibilty of system requirements on the WinXXX box. You get what you pay for and all PSUs included with cases are mostly rubbish. Do be afraid to spend good money for a name brand PSU (I don't mean case brand name either) - don't go under 550 - 600w for modern computer systems. (I speak from experience.)

Cheers Bazza

[dee4141]

I have had a PSU failure in the past which "fried" my processor - so I'm very wary. However the upgrade I'm considering would only add an extra 30W to a system that is currently running both smoothly and cool - also the total calculated requirement of 200W is still only 2/3rds of the (supposedly) 300W available.

PrinceGaz - I fed your computer specs into the PSU calculator and it came up with 285W minimum........so this PSU Calculator appears to give results broadly in line with your own findings.

If the 30W increase for an x1950pro is too much, then the alternative would probably be the HD2600XT - this gives a 15W increase, but doesn't require an additional power lead and is still an improvement on the X1300pro..... maybe I should err on the safe side...

[Potoroo]

However the upgrade I'm considering would only add an extra 30W to a system that is currently running both smoothly and cool - also the total calculated requirement of 200W is still only 2/3rds of the (supposedly) 300W available.

Stop thinking in terms of total nominal wattage. What matters is how the supposed 200W and supposed 300W are broken down into 12v, 5v and 3.3v - with 12v being far and away the most important.

On paper 12v 18A is enough to do what you want to do. Whether your PSU delivers a genuine 18A on the 12v rail I cannot say from here.

[PrinceGaz]

You can read PSU specs with the same credibilty of system requirements on the WinXXX box. You get what you pay for and all PSUs included with cases are mostly rubbish. Do be afraid to spend good money for a name brand PSU (I don't mean case brand name either) - don't go under 550 - 600w for modern computer systems. (I speak from experience.)

Cheers Bazza

Bear in mind it is an Antec case and therefore includes an Antec PSU, not some no-name piece of junk that has trouble supplying half the amount it is supposed to.

However dee4141: I'm a bit concerned that putting any big (either physically or power-hungry) graphics-card in your SFF cube-case could cause various problems. It might not even fit in the case, in fact that is probably the no.1 concern as power-supply issues won't matter if some other essential component prevents you inserting the card. Cards like the X1950 Pro are pretty long; nine inches (23cm) is typical. You might want to open your case and see if a card nine inches long would even fit in it (bearing in mind it will be the full height of the bracket at the end for the whole nine inches).

Even if it does fit, it could seriously interfere with the airflow in the case causing overheating problems elsewhere. You've got to be careful when upgrading SFF systems, you can't approach them in the same way as a standard midi-tower box.

[dee4141]

Here is a pic of the Antec case. The dimensions are 12in (L) x 10.5in (W) x 8in (H), so it is not as small as some designs. The footprint makes it large enough to accept a standard mATX motherboard - the ability to use standard components was one of the attractions.



Shown below is a pic with the side removed. The x1300pro card can be seen in place. This is a standard card and measures (above the slot) 6.5in (L) x 4in (H). There is sufficient room to fit a card 9in in length, but it couldn't be higher than 4in. The width of the card would not be a problem either, as the remaining slots are not used.

[PrinceGaz]

You should be okay then with the likes of an X1950 Pro or 8800GT sized card, provided it gets adequate cooling. One thing to watch for is that these cards are often slightly taller than other full-height cards, my 8800GTS which is based on the standard nVidia design has a circuit board roughly 5mm higher over its whole length than the top of the metal connecting-bracket to secure it to the case. That sort of difference makes minimal difference with a large case, but might be critical in a SFF case. And don't overlook the cooling aspect-- these graphics-cards need to be kept cool and if they are so large as to impede case-airflow, even if all other requirements are met you could end up with an overheating card.

Actually, given how graphics-card development tends to progress, and given the state RS is in currently, I'd recommend holding off till the next generation of cards, by which time RS will hopefully have received a comprehensive patch, and a card capable of running it is much less power demanding (not to mention smaller and much cheaper) than the equivalent today.

[jennings]

Got an Antec NeoHE 550W PSU yesterday - Easy to fit and can run rail sim with an X1950 - Get at least 20fps which is very good. I was a bit concerned at the temperture my PC was reading (Upto 34C) but i guess this is normal for these types of cards (My thermometer is at the bottom of my case).