Author Topic: Looking for a new PSU.  (Read 6487 times)

Offline JacksRag(e)

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Looking for a new PSU.
« on: Wednesday, February 27, 2008, 07:29:53 PM »
So I just got an 8800 GT yesterday, but have been holding back on installing it because of my weak ass PSU.  I've been looking around for sales on different PSUs and found this one.
What are your thoughts on this?  My current power supply just doesn't have enough amperage on the +12V rail (18A single rail, when the minimum is 26A).  This has two +12V rails at 18A, now I'm not too sure if you can add them up and use that, or if I'm just being a simpleton about the amperage.  Anyway, thanks for any advice in advance.

Offline scottws

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Re: Looking for a new PSU.
« Reply #1 on: Wednesday, February 27, 2008, 08:23:36 PM »
I never even knew you had to look all that deeply into the individual rails.  But look like you picked an Antec, so that's a good start. 

BTW, your link doesn't work.  The URL you have there is... weird.

Offline Pugnate

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Re: Looking for a new PSU.
« Reply #2 on: Wednesday, February 27, 2008, 11:04:42 PM »
Congrats on the 8800GT Hooby!

I'd say any brand name 550Watts would be more than sufficient. Recently, whenever I would start any game -- even chesss -- my computer would just instantly lose complete power. Turned out that my 5 year old Antec 500 was about dead, so I had to get a new one. This is what I got:

http://www.wccftech.com/forum/asus-a55ga-550w-psu-review-13590.html

By the way, I hear really good things about this:

http://www.corsair.com/products/hx.aspx

See if you can get that Corsair PSU. Got some solid reviews. I was going to get that initially, but it was out of stock, so I had to opt for the Asus.
« Last Edit: Thursday, February 28, 2008, 12:15:59 AM by Pugnate »

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #3 on: Wednesday, February 27, 2008, 11:47:15 PM »
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371004

How odd....the link I copied must have been..tampered with?  Dunno.  That's the one I'm looking at, though. hmm.

And I'll take a look at the other psus, too, pug.  The thing is I'm trying to keep this under a budget, this was a pricey little item and what with Patapon, Jeanne D'arc, Katamari, Disgaea already bought and then God of War and Smash Brothers next week..I don't know if I can afford much now.  ARGH.

Offline gpw11

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Re: Looking for a new PSU.
« Reply #4 on: Wednesday, February 27, 2008, 11:54:06 PM »
That's probably good. There was a website somewhere that not only had a breakdown of various PSUs but a little flash app where you could imput all your components and it would tell you what you could get away with.  I'll see if I can track it down.

I'm personally using a 450W, which isn't a problem, but might require an upgrade if I go 8800GT (I'd have to see what the power draw difference is between it and my current card).  I've always been told that the watts isn't the most important factor, but rather a combination of the brand and the watts.  Some cheaper PSUs may be rated for 500 or 600, but could crap out before that because they don't provide 'clean' power.  No, I don't really know what that means at all.  Now leaving thread.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #5 on: Thursday, February 28, 2008, 12:03:01 AM »
From all the research on the cards and whatnot, I've found that more important than the wattage of the psu it's the amperage.  If I remember, you have a 7900 gt, right?  You're ok on wattage, because even at high loads, the 8800gt is more efficient than the gts or gtx.  You're gonna want to check your +12V amperage, though.  You could have 500 or 600 watts, but if you don't have enough amperes going through the +12V rail, you're bottlenecking the card and also putting the card and your system at risk.

This clean power you're talking about, I think, has to do with the stability of the voltage and whatnot.  If your psu is rated at a certain wattage or voltage, but it dips back and forth, you're gonna be stuck with one unstable rig where it might reboot when the power dips and stuff...yea, that's as far as I understand it.  Eh.

And oh yea, the brand is important too.  I've consistently seen Corsair, Antec, Coolermaster, Rosewill seems to be well regarded on newegg,

Offline gpw11

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Re: Looking for a new PSU.
« Reply #6 on: Thursday, February 28, 2008, 12:13:11 AM »
I.....I love you hoob.

Offline gpw11

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Re: Looking for a new PSU.
« Reply #7 on: Thursday, February 28, 2008, 12:13:22 AM »
 :)

Offline WindAndConfusion

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Re: Looking for a new PSU.
« Reply #8 on: Thursday, February 28, 2008, 02:27:17 AM »
I've found that more important than the wattage of the psu it's the amperage.
God damn you, Jack.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #9 on: Thursday, February 28, 2008, 03:09:58 AM »
You're saying what matters most is current capacity at the +12V rails, right?  Because on paper at least, once you're in the DC circuitry, P=IV (power = current * voltage, or watts = amps * volts).  That does get complicated when you go over to the AC side, and of course, the power rating of the PSU is what it sucks out of your AC outlet.  It gets into calculus, which I've forgotten and I like it that way.  Suffice it to say that the actual AC power drawn is somewhere between a half and 3/4 of volts*amps, depending on magnetic fields, induction, and other such shit I don't want to think about.  In any case, given a fixed voltage, amps are directly proportional to watts.  So unless something besides the +12V rails is drawing lots of current away in the PSU, once you know the wattage is good, the amperage should be good as well (and vice-versa).  So it would seem anyway.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #10 on: Thursday, February 28, 2008, 04:08:44 AM »
Mmm, well what matters most when it comes to the newer generation of cards and those of us with older generation psus, more like.  My psu, from research and other folks' accounts, is nothing more than a 330 watt psu rebranded as 430 watts.  Sure, it could push out 430 watts under peak load, but it wouldn't hold up for extended amounts of time.  All this crap is unduly complicated. 
And cobra..that whole post scared me.
Well, from how I've come to understand it, the newer power supplies have dual +12v rails with 18 amperes across each rail.  Some of that goes to the cpu and the rest goes to peripherals.  My psu is single railed, so that 18 amperes is nowhere near enough to power the new card.
Buh.

Offline scottws

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Re: Looking for a new PSU.
« Reply #11 on: Thursday, February 28, 2008, 07:56:15 AM »
And oh yea, the brand is important too.  I've consistently seen Corsair, Antec, Coolermaster, Rosewill seems to be well regarded on newegg,
I've heard good things about OCZ PSUs as well, but they're crazy expensive.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #12 on: Thursday, February 28, 2008, 03:00:28 PM »
Mmm, well what matters most when it comes to the newer generation of cards and those of us with older generation psus, more like.  My psu, from research and other folks' accounts, is nothing more than a 330 watt psu rebranded as 430 watts.  Sure, it could push out 430 watts under peak load, but it wouldn't hold up for extended amounts of time.  All this crap is unduly complicated. 
And cobra..that whole post scared me.
Well, from how I've come to understand it, the newer power supplies have dual +12v rails with 18 amperes across each rail.  Some of that goes to the cpu and the rest goes to peripherals.  My psu is single railed, so that 18 amperes is nowhere near enough to power the new card.
Buh.

OK, so the problem is that the current capacity of the rail isn't high enough?  Keep in mind that the current drawn from each rail varies.  18 is just a limit.  If one rail draws much less current, there will be more power available to deliver current to the other rail.  But if the current capacity of the rail used for the video card is too limited, you're right.  It won't work right, regardless of the PSU's power rating, or power use through the other rail. 

Don't forget, though, that at a fixed voltage (12V here), there is a fixed max amount of current that can be delivered from a given power rating, regardless of how many rails you get.  I'm not sure why the number of rails would even matter, as long as the whole capacity of the PSU is made available to whatever you hook up to it.  If 18 amps is the overall limit, the max power draw can be figured out.  (See the formulas above.)  If that power number falls way below the PSU's rating, then the rating is a lie.  No?  Let's apply it here.  12V * 18A = 216 VA.  In a DC circuit, 216 VA = 216 watts.  That's all you can get out of a PSU at 12V with an 18-amp current limit.

Here's where I need to punt, though.  When you take that DC wattage over to its AC generation, it gets away from me.  There's all the shit I mentioned before, and there are conversion inefficiencies as well.  It could well be that it takes 450 AC watts to deliver 216 DC watts.  Seems like a huge loss to me, given that to get 450 watts AC, you need something like 800 VA AC.

You know what?  You're right.  You're absolutely right.  After trying to work through all this while posting, I've realized that to rely on the AC power rating doesn't get close enough to what you need to know.  You need to know the requirements of your card, and if current capacity at the molex plug tells you the whole story, you're better off.  So what is the max current draw of that card?

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #13 on: Thursday, February 28, 2008, 04:27:21 PM »
The manufacturer recommends a psu with at least 26 amperes across the 12 volt rail(s).  My old psu had a max of 18A across a single rail, enough to power the cpu and other peripherals, but not stable enough when you add in the 8800gt.  So, I ended up getting the Antec with 2 +12v rails at 18A each, giving me some decent headroom with 36A across the rails.  I installed it earlier and I've been chugging along quite well.  CoD4 and Bioshock look amazing maxed out, though I can barely play Crysis at medium settings at 1248x1024.  Buh.  Yea, I was with you for a while too, cobra.  But damn it, once you got into AC you lost me.  haha...thanks.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #14 on: Thursday, February 28, 2008, 05:43:02 PM »
Oh, but now I'm confused again.  If your card is hooked up to one rail, and that rail has an 18-amp limit, who cares that the PSU can deliver a total of 36 amps?  How does that help the card at the 18-amp bottleneck?

Edit:  Is the point that 18 amps is enough, as long as everything else is hooked up to the other rail?  It would still be nice to know what the card's max current requirement is.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #15 on: Friday, February 29, 2008, 12:07:07 AM »
What I found is that with multiple rails, the amperage adds up.  So, originally my single 12v rail gave out 18A.  But with my dual 12v rail, I get a total of 36A.  The minimum for amperage is 26A as stated, but I haven't been able to find the max requirement for current.  And I think that current is outputted as needed by the component.  So you've got the cpu pulling some current, and then most of the new cards come with the 6-pin molex converter that splits into two 4-pin molex plugs.  I've heard it's recommended to plug in a 4-pin molex from both rails so as to let the card draw the current when needed too. 
The thing with my new psu is that there's an actual 6-pin molex plug on it so that I just plugged it directly into the card instead of using the converter.  It's run well so far, so I'm not sure if I should go ahead and put the converter back in.  I might run some benchmarks and see if it makes a difference.  I'm just lazy at the moment.

Offline WindAndConfusion

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Re: Looking for a new PSU.
« Reply #16 on: Friday, February 29, 2008, 01:45:36 AM »
I'll ignore all the fucked up physics in this thread and just comment on the last post:

If you're connecting two 18 amp rails in parallel, that gives you 36 amps total. 36 amps at 12 VDC is 432 watts, which is roughly what your power supply is rated at. 26 < 36, so you're OK.
« Last Edit: Friday, February 29, 2008, 06:46:52 PM by WindAndConfusion »

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #17 on: Friday, February 29, 2008, 03:18:54 AM »
Basically, yea.  A lot of the power supplies are a bit deceiving in their descriptions.  They'll say 500 or 430 watts, but that's just the peak wattage and it's really not all that sustainable.  Have it running at max and you run the risk of frying the unit.  I'm sure I've got some things wrong and misunderstood in the thread, but I did learn a few things.  And my card's flying right now.
Except in Crysis.  Damn you, Crysis.

Offline scottws

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Re: Looking for a new PSU.
« Reply #18 on: Friday, February 29, 2008, 06:57:24 AM »
Dudes, you all don't know what you're talking about.  E=mc² and A²+B²=C² and C=2πr.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #19 on: Friday, February 29, 2008, 02:58:10 PM »
Haha!  A²+B²=C² is actually very pertinent.  In AC circuits, apparentPower² = realPower² + reactivePower², or VA² = watts² + VAR².  VA is volt-amperes, which you get from the simple DC equation P=IV.

Here's a link, for those of us who like to deal with the fucked up physics.

Offline Pugnate

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Re: Looking for a new PSU.
« Reply #20 on: Friday, February 29, 2008, 03:05:14 PM »
I have reported Cobra951's post to the moderators for hurting my brain.

Offline Quemaqua

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Re: Looking for a new PSU.
« Reply #21 on: Friday, February 29, 2008, 07:03:36 PM »
Math should be outlawed.

天才的な閃きと平均以下のテクニックやな。 課長有野

Offline scottws

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Re: Looking for a new PSU.
« Reply #22 on: Friday, February 29, 2008, 07:26:43 PM »
Haha!  A²+B²=C² is actually very pertinent.  In AC circuits, apparentPower² = realPower² + reactivePower², or VA² = watts² + VAR².  VA is volt-amperes, which you get from the simple DC equation P=IV.

Here's a link, for those of us who like to deal with the fucked up physics.
How do you know all this about electrical circuits?  That's one thing in math and physics that none of my classes ever covered.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #23 on: Friday, February 29, 2008, 08:00:48 PM »
I did learn all about the simpler equations in physics class.  I took 9 hours at OSU.  The AC complications I learned about way after, the first time I looked into uninterruptible power supplies.  They have a VA rating, and a watt rating which is much lower.  That intrigued me, so I looked it up.  The equations get into calculus--you have to do an integral, and that I've left way behind.  I hated freaking calculus.  (I took 12 hours of that.)

Offline gpw11

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Re: Looking for a new PSU.
« Reply #24 on: Saturday, March 01, 2008, 03:09:17 PM »
Did you ever figure out if you can add the 12V rails together?  Because upon checking mine, I have two both rated at 18A.  Combined, they're more than enough, but obviously they fall short individually. 

I've also looked at some newer ones, and most still seem to use 18A 12V rails, but have three or four of them as opposed to the two mine has. 

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #25 on: Saturday, March 01, 2008, 03:31:21 PM »
Yea, I found that what matters is the total number of amps you have.  You should be good with the number of amps for a 8800gt.  Not nearly good enough for SLI though.
Does your psu have a dedicated pci-x pin?  I noticed a lot of newer psus have one of those now.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #26 on: Saturday, March 01, 2008, 04:13:44 PM »
In order to add up the amperage capacity, the rails need to be hooked in parallel to your card.  W&C mentioned that, but is it possible?

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #27 on: Saturday, March 01, 2008, 04:33:29 PM »
Yea, it's recommended that if you use the 6-pin to double 4-pin converter that comes with the newer cards, you should plug in the 4-pin molex from the different rails.  My PSU had two sets of 4-pin molex plugs on separate cables, I assume that I should plug in one 4-pin from each cable.  That's what I gathered.  But fortunately, my psu also has a 6-pin molex plug, making the converter unnecessary.

Offline Cobra951

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Re: Looking for a new PSU.
« Reply #28 on: Saturday, March 01, 2008, 04:41:33 PM »
If you can skip an extra plug, you are definitely better off.  No possibility of excess heat in a pressure connection.  That's wild, though, 36 amps.  Haul out your car battery, and hook the video card up to that.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #29 on: Saturday, March 01, 2008, 06:03:51 PM »
I know, right?  And the 8800gt is fairly efficient compared to the big guns.  Imagine the current for a pair of 8800gtx ultras in SLI.

Offline gpw11

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Re: Looking for a new PSU.
« Reply #30 on: Saturday, March 01, 2008, 08:17:00 PM »
Sweet, thanks.  I don't know how I read right over that the first time.

and yeah, it's kind of insane how much power these things require.  I did, however, find that calculator I was talking about (actually, a different one that does the same thing), and it figures that at 90% load, I'll be using just under 350W   at 90% load.  That's with some upgrades I don't have at the moment.    So, I figure I should be more or less good with a buffer zone of 100W or so.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #31 on: Tuesday, March 04, 2008, 01:19:46 AM »
I'm curious about #C's "god damn you jack" post.  I just sort of assumed I had said something wrong.  Did I?

And so far, the machine's been perfectly fine.  Ran some DX10 games just to see the difference.  Lost Planet looks muuch much nicer.  As does the Witcher.  Bioshock is just as beautiful and it takes muuuch less time to load.  CoD4 is great.  Crysis...still kicks my system's ass, even at medium settings.  Argh.

Offline Pugnate

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Re: Looking for a new PSU.
« Reply #32 on: Tuesday, March 04, 2008, 01:54:58 AM »
Even at medium? Somethings not right then. Maybe you left anti aliasing on? I am using an 8800GTX and running on a mix of high and very high. Getting 25+ fps.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #33 on: Tuesday, March 04, 2008, 02:01:46 AM »
Could be?  I don't think so..I mean my computer's no slouch, but the game still jerks and skips a tiny bit when I play.  Buh.  I'll have to check the settings again.

Offline Pugnate

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Re: Looking for a new PSU.
« Reply #34 on: Tuesday, March 04, 2008, 02:03:07 AM »
Use fraps. What frames are you getting on average?

Offline WindAndConfusion

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Re: Looking for a new PSU.
« Reply #35 on: Tuesday, March 04, 2008, 02:04:31 AM »
Quote
I'm curious about #C's "god damn you jack" post.  I just sort of assumed I had said something wrong.  Did I?
This whole thread is partially wrong and partially right, but if I complain about it no one will care and I'll get called a smartass.

And stop calling me #C. #C is the name of a Bosnian serial killer, still at large, and I'm sick of getting arrested by Interpol.

Offline JacksRag(e)

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Re: Looking for a new PSU.
« Reply #36 on: Tuesday, March 04, 2008, 02:05:58 AM »
I thought it was something to that extent.  Just curious.  Either way, whatever you would have said, I think I was gonna go ahead and call you an asshole, anyway.

Asshole.

#C

Yea, so I'm averaging just about 25 fps, also.  But there will be random jerkiness in the game.  It's odd.  But it's definitely much less than the last time I played.  Odd.

Offline gpw11

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Re: Looking for a new PSU.
« Reply #37 on: Tuesday, March 04, 2008, 02:23:11 AM »
Please refer to my "hey we don't really know how to code for shit so we're just going to throw in some more foliage and graphical effects to trick people into thinking there's a reason our game runs like ass.  Scale it down?  WE CAN'T SCALE IT DOWN. You don't deserve to live if you don't have quad SLI anyways" post.

And that's why I think it's retarded when people compare Crytek to ID, Epic, or even Valve.


Offline Pugnate

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Re: Looking for a new PSU.
« Reply #38 on: Tuesday, March 04, 2008, 09:54:28 AM »
Please refer to my "hey we don't really know how to code for shit so we're just going to throw in some more foliage and graphical effects to trick people into thinking there's a reason our game runs like ass.  Scale it down?  WE CAN'T SCALE IT DOWN. You don't deserve to live if you don't have quad SLI anyways" post.

And that's why I think it's retarded when people compare Crytek to ID, Epic, or even Valve.



I think I was the only one who compared Crytek to those companies on these forums :P.

You are partially correct on the lack of scaling, but the rest of it, I disagree with. I know you were being facetious with the SLI comments, but here is what I think: 

1. I am getting an average of 25 fps at a resolution of 1440x900 on high settings using a system not significantly better than this. That PC you can build on NewEgg without the Windows CD for about $750. The system was recently tested on Maximum PC with Crysis running on high on a 19'' monitor, and earning 30+fps second. So yea, the quad SLI thing is normally something echoed by console gamers with a bone to pick.

2. a) You mention ID software, but keep in mind that similarly to Epic or Valve, they have never released a cutting edge engine that rendered anything other than closed environments.

b) When Quake III was released, fanboys were in an uproar of Crysis proportions, because the game ran like ass on even the most modern of systems at maximum settings. That was something the Quake fans weren't expecting, and it took nearly a year for technology to catch up with Q3. The problem with Crysis has been the marketing, and the fact that ATi pushed the GPU market a year behind schedule.

c) People forget that the Xbox 360 is capped at 30 fps in its shooters. So isn’t getting the same on a PC (that also has to shoulder Windows) just as acceptable? The only point where you can compare Epic or Valve to Crytek is in the internal environments, of which are many in Crysis. In the underground settings of Crysis, I found the game looked technically better than Unreal Tournament 3, and was running at over 80 frames per second.

3. On that $750 machine I pointed out, PC Gamer magazine benchmarked Crysis on medium settings and were getting an average of 58 frames per second. You might argue that Crysis on medium doesn't look nearly as good as high, but it still looks gorgeous. In fact at medium Crysis looks better than Gears of War, Half-life 2, Halo 3 and Doom 3. Of course there is little comparison to those static environments, because Crysis renders gorgeous terrains with dense foliage affected by environmental effects in real time; trees sway, leaves rustle, water ripples etc. When you compare Doom 3 or Unreal Tournament to Crysis, the only life you will see from the former two, is in the form of enemy AI, limited object destruction (read: crates), and physics. 

The only games that can be compared to the open ended environments of Crysis are Operation Flashpoint, Ghost Recon, Oblivion, and S.T.A.L.K.E.R. All of those look worse than anything in Crysis, and ran each poorly at launch. The best of the bunch is Oblivion, which at max settings runs at 30fps on my system, yet pales in comparison to Crysis.
Finally, have a look at the screenies I took. Some of that looks near photorealistic, don’t you think? And it feels even better when played through. If you look at pretty screenies from Epic or ID games, the still frames will be about as static as the actual game. 










Offline scottws

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Re: Looking for a new PSU.
« Reply #39 on: Tuesday, March 04, 2008, 10:52:39 AM »
I totally disagree with the notion that Crysis looks gorgeous on medium settings.