Personal PSU Controversy - What the f---?

[Sovereign]

So I have a PC Power and Cooling 850SSI, which was basically the biggest, most badass power supply ever when I bought it for my gaming system last May. However, I am having a large number of issues that some are tracing to the power supply. Not that the power supply is faulty, but rather that there's simply not enough power to go around. By sheer wattage it seems OK, but I've been told that watts aren't everything.

The PSU has four 12v rails rated at 17A each. If my understanding of power supplies is correct, if one has multiple rails, and power is not utilized in one rail, it becomes trapped in that rail and the rest of the system can't touch it. Also, I have been told that dual 7900GTX SLI requires 2x22A rails (separate or on one big rail). This power supply has four 12v rails rated at 17A each and two PCI-E six pin power connectors. Each of these feeds a 7900GTX graphics board. Three SATA cables feed three hard drives, and two molex connectors drive two optical drives and some fans (there are eight molex power connectors total on two strings of four each). All mobo connectors are correctly attached, including the extra four-pin that plugs in for SLI systems!

The system configuration is as follows:
CPU: Opteron 170 at stock speed, 2.0GHz
RAM: 4GB DDR500 @ 400
MOBO: Asus A8N32-SLI Deluxe
HDD1: 150GB Raptor
HDD2 & 3: 250GB Caviar
GPU: Dual 7900GTX SLI
PSU: TurboCool 850SSI
OS: Windows Vista Ultimate x64

I have been told by a system integrator friend that my power supply is not enough. His logic is that each card by nVidia spec needs 22A, and I only have dual 17A, which starves my cards. I have further found this Thermaltake 250 watt dedicated graphics power supply (http://www.newegg.com/Product/Product.aspx?Item=N82E16817153037) which supplies 21A (max of 25A). nVidia certifies it for dual 7900GTX SLI as long as I have another power supply off their "All other SLI Configurations" list. The 850 certainly outstrips those units.

The solution based on these assumptions is to purchase the following:
- A Thermaltake 250w dedicated graphics unit
- A 2x PCI-E to 1x PCI-E joiner OR determine whether the four pin molexs are on different rails and if so, use a molex-to-PCI-E to combine the two

All I have to say to all this is :wtf: mate?

Note that none of these problems ever occurred under Windows XP with only 2GB RAM installed. I had a K8N Diamond Plus die on me, the PCI slot failed and I don't know if this was a manufacturing defect or a result of not enough power. Please enlighten me.

[Oklahoma Wolf]

His logic is that each card by nVidia spec needs 22A, and I only have dual 17A, which starves my cards.

His logic is faulty - each card will need less than 8A.

Your PSU should be fine for that system - what issues are you having?

[John]

Also, I have been told that dual 7900GTX SLI requires 2x22A rails (separate or on one big rail).

22A = 264W

A single 7900GTX pulls less than 100W (<8A) under a load.

The system configuration is as follows:
CPU: Opteron 170 at stock speed, 2.0GHz
RAM: 4GB DDR500 @ 400
MOBO: Asus A8N32-SLI Deluxe
HDD1: 150GB Raptor
HDD2 & 3: 250GB Caviar
GPU: Dual 7900GTX SLI
PSU: TurboCool 850SSI
OS: Windows Vista Ultimate x64

I have been told by a system integrator friend that my power supply is not enough. His logic is that each card by nVidia spec needs 22A
Your friend is way out in left field. :rant: It was recommended that you use a 500-550W psu w/ 30-34A (which covers the the entire system) when running 7900GTX SLI.

Example: http://www.bjorn3d.com/read.php?cID=891&pageID=2103

All I have to say to all this is :wtf: mate?
Exactly, you don't need a new psu.

*** It looks like the wolf beat me to the prey. :P

[Sovereign]

OK the issue is that I cannot boot correctly with SLI enabled. If I do so, no matter what drivers I use, I get a black/white strobe instead of my Windows logon screen. I have the latest BIOS as well.

[Zap]

RAM: 4GB DDR500 @ 400
OS: Windows Vista Ultimate x64
----
Note that none of these problems ever occurred under Windows XP with only 2GB RAM installed.
----
OK the issue is that I cannot boot correctly with SLI enabled. If I do so, no matter what drivers I use, I get a black/white strobe instead of my Windows logon screen.

So, adding two more GB of RAM put your system over power specs? I think not! What else has changed? Oh yeah, Vista 64 bit.

IMO that is the culprit. Leaving the extra RAM in there, install Windows XP (regular 32 bit) and see your problems disappear. :) That advice will be $20, please send Paypal.

Reason #1 64 bit OS can be quirky. At work we have high end Dell Precision 690 workstations running with 16GB FBDIMMs, dual 2.66GHz Woodcrest CPUs, Quadro FX 4600 video cards, 1kW power supplies... and running XP64. I hate those things. :@ Some engineering apps crunch stuff really well, but regular Windows tasks can be sooooo slow. Let's not get into the apps that don't work properly...

Reason #2 SLI drivers are still kind of broken for Vista.

Going to 32 bit Windows XP will lose a bit of RAM, so you'll be running around 3GB RAM instead of 4GB. Don't sweat it.

[jcgamo88]

Actually he could be running upto 3.5GB ram depending on how many PCI cards he's got plugged in. Judging from your specs you've got 3 cards in there. Two gfx cards and a sound card.

Honestly I haven't researched enough to be qualified to make this estimate but I'd think XP 32 bit might be able to address upto 3.2GB for you. Which would far more than you'd need anyway!

/my useless tidbit

[jonnyGURU]

I've had Vista 32 see anywhere between 2.5 and 3.5GB depending on the weather. I haven't been able to figure out the exact variable that changes the amount of RAM that comes up, but it seems to be different with each build.

Other than that, I'm still having problems with Vista and SLI and Vista and dual monitors. It just seems the drivers still aren't where they need to be for Vista.

Since Vista is such a huge variable, I would use XP to trouble shoot. And if the problem is still there, I would have to try one card at a time (not just enabling/disabling SLI) to see if the problem is just a faulty card. Don't know what's up with video cards these days, but just in the last month I've had an 8800GTS go completely dead and one of two 7900GT cards cause BSOD's after being installed in the rig for no less than a year. Weird.

[C'DaleRider]

Which ForceWare driver version are you using for your video cards?

I only ask because in nVidia's ForceWare Release 162.22, it was supposed to fix a Vista 64 issue with the 7900GTX in SLI and 4GB of RAM.......

From nVidia's release notes for ForceWare 162.22:

Listed under Fixed Issues–Windows Vista 64-bit

"GeForce 7900 GTX: On systems with 4GB of memory, the screen
goes blank when enabling SLI mode. [326183]"

(From page 14 of Release 162 Notes)


I just wonder if this is the same sort of issue you're having......

[Sovereign]

Which ForceWare driver version are you using for your video cards?

I only ask because in nVidia's ForceWare Release 162.22, it was supposed to fix a Vista 64 issue with the 7900GTX in SLI and 4GB of RAM.......

From nVidia's release notes for ForceWare 162.22:

Listed under Fixed Issues–Windows Vista 64-bit

"GeForce 7900 GTX: On systems with 4GB of memory, the screen
goes blank when enabling SLI mode. [326183]"

(From page 14 of Release 162 Notes)


I just wonder if this is the same sort of issue you're having......

Yeah, right nVidia. I call bullsh-t! The 158.xx (can't remember which exact version) was working fine until I tried to upgrade my chipset drivers, after which I got this SLI Strobe, as I call it.

I can try dicing the drive and installing XP, but I don't think I'll "see" any more than 3GB RAM because each 7900GTX takes up 512MB of address space and then there's the rest of the system.

So essentially it boils down to this: why did it work, but when I reformat and installed (to the best of my knowledge) the exact same drivers, does it NOT work?

I've tested each card individually in Vista and they both run fine (3DMark loops, games etc), I went to a LAN party and ran one card the whole night (6+ hours of games). Not saying anyone is wrong, just reporting what I've done to try and help us narrow this down.

And isn't XP x64 driver support even worse than Vista x64?

ARGH! :wall:

[Bun-Bun]

Yeah, right nVidia. I call bullsh-t! The 158.xx (can't remember which exact version) was working fine until I tried to upgrade my chipset drivers, after which I got this SLI Strobe, as I call it.

I can try dicing the drive and installing XP, but I don't think I'll "see" any more than 3GB RAM because each 7900GTX takes up 512MB of address space and then there's the rest of the system.

So essentially it boils down to this: why did it work, but when I reformat and installed (to the best of my knowledge) the exact same drivers, does it NOT work?

I've tested each card individually in Vista and they both run fine (3DMark loops, games etc), I went to a LAN party and ran one card the whole night (6+ hours of games). Not saying anyone is wrong, just reporting what I've done to try and help us narrow this down.

And isn't XP x64 driver support even worse than Vista x64?

ARGH! :wall:

Yes but what the others recommended is you revert back to XP 32bit.

Driver support for Vista just sucks. Go to the nvidia forums (actually don't because they are useless) and you will find tons of people moaning about lack of SLI in Vista and yadda yadda... I am sick of it. XP was broken when it first came out and no where is the company obligated to make SLI work when only 1% of their consumer base use it. (BTW I pulled that number out of my head... could be completely wrong.)

Install XP 32bit, and be happy. Don't even think of vista until some serious updates have been done on both vendors and microsoft's part.

If you still have problems after installing XP 32bit then you can come complain to us some more ;) (or try the latest drivers that just came out a couple days ago before reinstalling XP 32bit)

EDIT:

BTW if you think 850watt isnt enough for your rig... look at mine in the sig... thats off a 700watt and theres still room to spare... so yeah... ;)

[Sovereign]

What about Vista SP1? I read that it "fixes compatibility with certain hardware" and "improves functionality with high-end graphics cards" or something like that...

I'm pinning my hopes on that.

[signmeuptoo]

The soonest SP1 will come is later in 2008 IIRC, if then. MS has their heads up their...

[MrWicked1968]

why do your 7900GTX's take up 512mb of address space? they're not turbocache cards. there's no reason for them to use any system memory.

[jcgamo88]

why do your 7900GTX's take up 512mb of address space? they're not turbocache cards. there's no reason for them to use any system memory.

I was wondering about that too. I believe he's confused about the gfx cards actual onboard memory.

So I did a tad more research. Thanks to the good old 32bit computer architecture a 32bit processor can only address upto 4.2 billion unique bits of address space. The pagefile that windows creates is counted as system memory. If the pagefile is set to 1gb then windows will only see 3gb RAM in the system.

But I think generally once the RAM size increases (if XP is set to manage virtual memory automatically, this is default) then the pagefile size will be lowered.

In addition to this, anything on the PCI bus (AGP, PCI, PCIx, PCIe, ISA, etc) also uses address space. And so the maximum addressable RAM is again lowered.

It's a very common occurrence actually. I've always known it happened, just was enver sure why.

[signmeuptoo]

Good information to know!

[mp666]

why do your 7900GTX's take up 512mb of address space? they're not turbocache cards. there's no reason for them to use any system memory.

He's talking about address space issue which will be seen when you have lots of memory (3 to 4 GB) and running a 32-bit system. This is a shortcoming of old intel 32-bit x86 architecture and consumer OSes and chipsets.

[mp666]

Thanks to the good old 32bit computer architecture a 32bit processor can only address upto 4.2 billion unique bits of address space.

Actually the limit for 32-bit Intel compatible architecture is 64 GB. And that's for one chipset and cpu.

The pagefile that windows creates is counted as system memory. If the pagefile is set to 1gb then windows will only see 3gb RAM in the system.


Are you saying that if someone had 4 GB of RAM and set the pagefile to 1 GB windows will think there is 3 GB of system memory ? Many people who need large swap space run their system with for example 2 GB of RAM and pagefile set to 4GB. Will windows see -2GB of RAM ? :D

But I think generally once the RAM size increases (if XP is set to manage virtual memory automatically, this is default) then the pagefile size will be lowered.


Nope. XP use a very simple algorithm for pagefile size. It multiplies the amount of RAM by 1.5. This is not a perfect way of doing this. Because in general you'll need less swap space when you have more RAM. If you don't need to have full memory dumps you don't need a huge swap. And you can't have a pagefile that is larger than 4 GB. But you can create multiple pagefiles if you need to.

In addition to this, anything on the PCI bus (AGP, PCI, PCIx, PCIe, ISA, etc) also uses address space. And so the maximum addressable RAM is again lowered.

True but as an aside don't forget that Windows knows how much memory you have, it just shows the addressable amount. People who are using XP-32 bit can check this by :
1. Right clicking MY computer and choosing properties. You'll see the lower amount here.
2. Start/Run/Msinfo32. In system summary (if you don't have a buggy BIOS etc) total amount of physical RAM will be shown as 4096 MB.

[Per Hansson]

Regarding the RAM issues you asked about: A 32 bit OS only has a 4GB Virtual Address Space

It also has a 4GB Physical Address Space

The Virtual Adsress Space is devided up in a 32 bit Windows OS with 2GB for the kernel and 2gb for applications (so any single app can't use more than 2gb...)

But in the Virtual Address Space the memory maps for the graphics card must also be located, so if you have 2x 256MB GFX cards you will remove 512MB from the total, thus you will only be able to use 3.5GB of physical memory. Plus there is more stuff that requires memory maps, so usually you will end up at about 3gb of usable memory on a 32 bit OS

More info here: http://www.dansdata.com/askdan00015.htm
There are also two articles on Anand about it...

[mp666]

Regarding the RAM issues you asked about: A 32 bit OS only has a 4GB Virtual Address Space

It also has a 4GB Physical Address Space

That's not entirely true. A 32-bit OS can address more than that. It will have to use ugly remappings etc but it's possible as address width of x86 architecture is 64 GB with a single CPU. 32-bit Datacenter edition of W2003 can address up to 128 GB and 64-bit one up to 1 TB.

The Virtual Adsress Space is devided up in a 32 bit Windows OS with 2GB for the kernel and 2gb for applications (so any single app can't use more than 2gb...)

True but can be upped to 3GB with a boot.ini switch. However, that's more for testing or server usage.

But in the Virtual Address Space the memory maps for the graphics card must also be located, so if you have 2x 256MB GFX cards you will remove 512MB from the total, thus you will only be able to use 3.5GB of physical memory. Plus there is more stuff that requires memory maps, so usually you will end up at about 3gb of usable memory on a 32 bit OS


Yup.

More info here: http://www.dansdata.com/askdan00015.htm
There are also two articles on Anand about it...

I've read dansdata article some times ago and I can recommend it. I don't know much about the Anand articles.

[Per Hansson]

Here are the two articles I mentioned:

http://www.anandtech.com/gadgets/showdoc.aspx?i=3034
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3044

They supplement the dan's data article quite well

[Sovereign]

...ahem.

My patience has been rewarded by Microsoft Hotfixes!
- Microsoft Hotfix 929777 (4GB RAM memory addressing problem)
- Microsoft Hotfix 938194 (General compatibility fix)
- Microsoft Hotfix 938979 (Overall performance update)

Installing that batch makes everything work great. The 4GB RAM (they call it the "can't boot with over 3GB RAM" fix on Microsoft.com) fix is common and has been suggested for any system running 4GB RAM.

Hotfixes 938194 and 938979 have not, as far as I can tell, been marked "beta" but nor have they been pushed via WU yet. Those two seem to have corrected the "SLI Strobe" I was experiencing as I no longer have the issue. I'm guessing credit goes to 938194 because it is labeled "compatibility."

[jcgamo88]

Great to hear you got that fixed. I've been away for almost two days because my router borked itself.

Else I would have said to mp666, That info would ahve been relevant about 2 days prior when I amd emy first post in this thread X(

Geez, leave someone who absolutely has no clue to google for something that he doesn't know how to. Shame on you for waiting so long! :P

[Bun-Bun]

Glad you got that working.

On the addressing issue... A 32bit bus can only address 4GB worth of bits. This may be possible with different codeing practices as Windows server has been able to get around this limitation but the limitation in the architecture is still there.

But talking about that is moot as we are discussing Win XP/Vista 32bit which are limited to 4GB virtual/physical address space. Which is why I won't go Vista because I would hit the 2GB threshold very quickly when playing supreme commander... once they fix the memory issues in vista in regards to video cards taking up far too much in games then I will consider switching...

[Sovereign]

Wait does SupComm still have a memory issue under Vista x64? I have 4GB RAM and if SupComm runs out on me heads will roll...

[Bun-Bun]

Wait does SupComm still have a memory issue under Vista x64? I have 4GB RAM and if SupComm runs out on me heads will roll...

You may have to flag it so that windows gives it a larger virtual space. By default applications that arnt flaged to support larger memory windows will treat as legacy and still only give 4gb virtal space (and thus only 2GB to the game itself).

Anandtech had two very good articles on this. Once flagged properly (you edit a .exe file and change a header to flag it) Supreme Commander will have no issues in Vista 64bit.

EDIT: Latest revisions of the game shipping out are already flagged to use more memory. And work is being done with the expansion to better memory manegment.

[Sovereign]

It doesn't currently have any issues, I was just wondering if it is possible. I played it on 2GB/max/XP for several hours (3+) and never had a crash, now mind you this was against a single human opponent on a LAN, not a massive multiplayer with AI.

[mp666]

Here are the two articles I mentioned:

http://www.anandtech.com/gadgets/showdoc.aspx?i=3034
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=3044

They supplement the dan's data article quite well

Thanks. I remember reading the first one. Both have interesting points. The first one also makes the common mistake of thinking that Intel 32-bit systems are limited to 4 GB but otherwise good reads. I also learnt that now using BCDedit you can adjust memory amount for user space in Vista (for XP it's either the default 2/2 or 3/1 with a boot.ini switch). Now you can choose different sizes. I will play with this later.

Have a nice day.

[Per Hansson]

Thanks. I remember reading the first one. Both have interesting points. The first one also makes the common mistake of thinking that Intel 32-bit systems are limited to 4 GB but otherwise good reads. I also learnt that now using BCDedit you can adjust memory amount for user space in Vista (for XP it's either the default 2/2 or 3/1 with a boot.ini switch). Now you can choose different sizes. I will play with this later.

Have a nice day.

Just saw a new article:
http://www.anandtech.com/systems/showdoc.aspx?i=3060

Have not read it yet...

[mp666]

Read it. It's not really about the 4 GB problem but nevertheless an interesting read. It shows that the fix from MS really fixes something.

[Per Hansson]

Read it. It's not really about the 4 GB problem but nevertheless an interesting read. It shows that the fix from MS really fixes something.
Yea I did read it
Interesting info for sure

After SP1 or SP2 Windows ME 2 might actually become a usable OS ;)

[mp666]

Yep. I have Vista but I don't use it. I'll be playing with it for learning more but for a production system as always I'll wait the first service pack at least.