Corsair 520HX or 750TX - any reason not...

[oneblue]

I'm building a system and am thinking of buying the Corsair 750TX.

I don't really that much power right now, but for $10 more (after rebate) than the 520HX I can get the 750TX. As I understand it, the PSU is only going to use the amount of power the PC draws, so I don't think I'm chewing up up energy. I like the fact that I have that I that much more flexibility for $10 (I have multiple harddrives, will have a high end video card, will probably go quad core at some point, etc., etc.).

Is there any reason NOT to buy the 750 for $10 more? Some obvious thing I am not seeing?


(or, is there a reason I'd want to spend $25 more than the 520HX for a 620HX?)

[cypherpunks]

If a noticeable fraction of their power losses don't depend on load, then they can be very efficient at higher loads but terribly inefficient at 25% loads.

However, the TX750 stays efficient down to 30% load (225 W) at least, so shouldn't do too badly. And actually, it's a couple of points more effiicient than the HX. So the 750 will be fine in this case.

Just remember that with a power supply that's honestly rated, you need a lot less power supply than you think. Even a pretty high-end machine, as long as it only has one GPU, pulls around 200W at full load. That 750W supply will be positively loafing.

Here's a system like yours, with a quad-core processor, 8800GTS video card, and three hard drives (one a raptor) that peaks at 218W during gaming while writing a DVD.

People are so used to bullshit ratings on cheap junk power supplies that they have no idea how much (or more to the point, little) power they actually use.

[Stefan555]

The main difference between the HX serie and the TX serie is; HX has modular cabling, TX not.

[spursindonesia]

@Cypherphunks, while i agree that overestimation does happen quite often, i wonder whether the example that you've presented there really gives us the right picture of a system power consumption.

I mean, that looks a bit on the lower extreme of a measurement result, doesn't it ? Did the tester use proper tools when measuring power consumption on his rig ?

[jonnyGURU]

It is strange since we see HardwareCanucks test non-overclocked rig pull well over 200W just doing th efficiency tests (running Company of Heroes) which is a 3800+ with a single 8800GTS card.

Overclocked, he typically pulls almost 300W.

Naturally, SLI and Crossfire figures are much higher.

[Spectre]

Originally Posted by cypherpunks

If a noticeable fraction of their power losses don't depend on load, then they can be very efficient at higher loads but terribly inefficient at 25% loads.

However, the TX750 stays efficient down to 30% load (225 W) at least, so shouldn't do too badly. And actually, it's a couple of points more effiicient than the HX. So the 750 will be fine in this case.

At 184w load at 45c the TX750 was 81.41% efficient.

http://www.hardocp.com/article.html?...50aHVzaWFzdA==

Just remember that with a power supply that's honestly rated, you need a lot less power supply than you think. Even a pretty high-end machine, as long as it only has one GPU, pulls around 200W at full load. That 750W supply will be positively loafing.

My wife's system pulls more than that...............................

[cypherpunks]

Originally Posted by Spectre

My wife's system pulls more than that...............................

Just out of curiosity, what's in it? I should perhaps clarify that I meant pull from the power supply, for comparison with the power supply's rating, not pull from the wall (that will be 25—33% higher given a 75–80% efficient supply), and I did mean "about 200" to mean "a lot closer to 200 than 300".

Things that I know require budget adjustments:

• P4s can be pretty power-hungry. +50W.
• Obviously, dual processors (by which I mean dual sockets) take more. +100W.
• Dual GPUs (SLI/Crossfire) will blow the power budget completely to hell.
• Overclocking, particularly the associated overvolting, can bump power consumption significantly. +75–100W.
• Hard drives (standard 7200 RPM 3.5 inch) pull about 12W operating and 35W spinning up. (And older, larger ones pulled even more.) +12W, and ensure the spin-up surge is under the maximum.

If you haven't got one of those factors and are pulling more than 230 W from the PSU, I'm curious what's in the box.

Most PSUs are happiest running at about half of maximum capacity, so I consider 350W a good rating for most computers (300W if you have really wimpy or on-board graphics), and 400W to have plenty of headroom. 500W is overkill, but not totally insane.

For most people, a PSU of over 500W (which is every PSU that Corsair makes, except for one!) is just crazy. You'll never use that much. I have a busy server with 8 hard drives running very happily off an old Enermax EG365P with only 17A on the +12V rail. (Although, y'know, the math on the spin-up surge on +12V suggests that it shouldn't work. I ought to break out the kill-a-watt and see what it's pulling.)

[jonnyGURU]

Originally Posted by cypherpunks

For most people, a PSU of over 500W (which is every PSU that Corsair makes, except for one!) is just crazy. You'll never use that much. I have a busy server with 8 hard drives running very happily off an old Enermax EG365P with only 17A on the +12V rail. (Although, y'know, the math on the spin-up surge on +12V suggests that it shouldn't work. I ought to break out the kill-a-watt and see what it's pulling.)

Emphasis on "most people."

Most people don't run dual procs or dual (or sometimes three) graphics cards easily needing 550W to 800W of power.

Of course, most people also wouldn't know a decent PSU if it bit them in the ass.

[cypherpunks]

Originally Posted by jonnyGURU

Emphasis on "most people."

Most people don't run dual procs or dual (or sometimes three) graphics cards easily needing 550W to 800W of power.

No question; those german guys benchamrking Crysis on three 8800 Ultras needed a 1 kW supply.

Of course, most people also wouldn't know a decent PSU if it bit them in the ass.

It just drives me up the wall that common perceptions have been so warped that people think a decent 350W supply won't be enough and they should get a 650W supply instead.

[Spectre]

Why is it you assume none of us have a clue?