X1900 Crossfire and Tagan TG580-U15 PSU advice

I had installed a X1900XTX and a X1900 Crossfire card in my project build parallel HEX and ran into a bit of a problem.

When I really pushed the system hard and run a benchmark or play a game, a good few minutes in to it the system completely shut down. No warning, no artifacts, no slow down - just bam! It's like someone has just pulled the power cord from the wall (system leds on the motherboard are still on).

This was happening all the time running HL2 Hi Res Pack, X3 benchmark demo, with the following settings in CCC:
Resolution - 1920x1200
Crossfire - enabled
AA - 14X
Adaptive AA - Quality
Anisotrpoic Filtering - HQAF 16X
CAT AI - Advanced
Mipmap Detail Level - Quality

Those games ran like oil on teflon and looked amazing before the power cut. I then ran 3dmark06 with the above settings on default and it was happening too, but wasn't as predicatable or sure-fire.

The system spec are:

AMD X2 4400 @ 2.64Ghz stock cooler
2 x 1Gb Ballistix PC4000 @ 240Mhz, 2-2-2-7 1T
DFI RDX200
X1900XTX stock setting
X1900CF stock setting
WD Raptor 74Gb
WD 400Gb
Tagan 580W psu

Now I was pretty sure the power shutdown wasn't due to heat, as the system would run less maxed out without a hitch. It's only when the newly added Crossfire setup demanded more power that this happend.

The power advisory leaflet that came with my X1900's states that it requires 30A on the 12V for single card, and 38A on the 12V for Crossfire. That's a lot of ampage!

I started to think the Tagan TG580-U15 psu wasn't up to the job, even with it's 580W's. The TG580 has 2 12V rails, and a switch with led to change to/from split and combine mode. In split mode (what I had it set to) it is rated to 20Amax on each 12V rail, 35A total (understand that ). In combine mode the single 12V rail is rated at 35A. That's 3A under the recommended psu requirements from ATI.

The description of this 12V rail switch in the manual didn't translate very well and makes you think that it should switch automatically - "when the +12V rails is over 20A the switch will jump into 'Combine' mode, the blue LED will light up automatically". I ran the X3 demo that I knew would cause the shutdown and watched the blue led for this switch. Sure enough, right at the time the system shutdown, the blue led flickered briefly before the power was killed.

I manually put the switch to 'Combine' mode and re-ran the test. Right at the point of the X3 demo where it had died before, this time the blue led would come on and go out a few times, presumably indicating that the 12V rails had exceeded 20A. No system shutdown! Woot!

What does this tell us?
- if you are running a high load dual gpu set up and a Tagan TG580 psu, set the switch at the rear of the psu to 'Combine'.
- the rail switch on the Tagan doesn't "jump" like the manual suggests
- if you want to run a simillar setup with a different psu, make sure the psu can handle more than 20A on each rail, or can be combined (more if you have more 12V devices)
- are psu's with 'un-conbinable' separate 12V rails of 20A or less no good for Crossfire setups?
- the X1900 Crossfire config takes a shed load of power at high resolutions and detail
- I reckon the total ampage on the 12V rail is only slightly above 20A, from watching the behaviour of the blue led at the back of the psu
- there should still be enough redunancy left in the 12V rail to overclock the X1900's and connect more devices (pumps, fans)

Sorry for the long post, but hopefully I have explained this well enough and others won't have problems, and future builders can select their psu's with better understanding.

I'll post a link to this thread in the Power Supply forum so they get to read it too.

Try ATI Tool and check out how much amp your GPU is drawing from the power supply.

Can you post a screenshot of ATI Tools?

I'm looking to see if I can connect another monitor while I'm in Crossfire mode and then move all the monitoring software stuff to that monitor. This will allow me to watch the power while in full load. Don't know if it's possible or how I can capture it while playing a game though!

Manoj said:

Try ATI Tool and check out how much amp your GPU is drawing from the power supply.

Can you post a screenshot of ATI Tools?

Click to expand...

That will not give you the proper amp rating. That is the amps being pushed at the lower voltage to the core, not the 12 volt rail amperage being drawn...

I should have guessed this, but I can't run an extra monitor while in Crossfire mode. There goes that idea.

I am also running X1900XT Crossfire and I have the Enermax Liberty 620W power supply. I don't get any shut down problems when running games at 1900x1200.

The Enermax Liberty 620W has Two 12V rails with 22A each. Combined is only rated as 36A.

I am looking to buy a new power supply with 750W soon. I think I need is because I also have a Pentium D 955XE @ 4.7Ghz.

wow - glad I saw this one.. I was thinking about buying a tagan 650 with the same rail "bonding" (combining) ability as stated in the OP... this psu:

http://www.meritline.com/epower-silents-engine-tiger-650-p5-power.html

it's got 2x 20amp +12v rails, but can run them as one rail for 45amps combined.. seems like a good PSU for the $. and I guess the single rail mode does work, so this 650 might not peg out to max...hrm........

Also, there's a 750 tagan here:
http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=177&products_id=3818
that was my next choice... it can run in 4 rail mode, or 1 rail mode also.. looks nice.

Revenant, I have a confession to make regarding this PSU - when the load exceeds 20A (combine mode) and the blue LED comes on, the PSU makes a strange noise. It's hard to describe, but it's created by vibration of heatsinks or the laminations of the transformer when the load gets high.

This probably won't affect other Tagan psu's, as when I first got the PSU, it had a nut loose inside it. Luckily I heard the rattle before I switched it on! I got the nut out and decided to keep the psu and it's been working fine ever since. It was only after adding the monster load of two X1900's that the noise became apparent. That little nut has came back at bit me in the ass!

I'll have a look at where it came from and put it back when I mod the psu - to take the load monitoring blue LED from the back of the psu to the front of the case.

Edit: Rattlesnake, that's what the psu sounds like when the current draw is over 20A and the led comes on!

Thanks for the info (confession).. I am going with the 750W one now... I don't want to mess around. It's got a hard switch for making the +12v one rail with 40+ amps... I'll run it like that. w00t.