Reviews - Corsair HX520W 520W
Sample Provided by: Corsair (By jonny on Tue, Aug-15-2006)

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     Now that you've all had a chance to digest the plethora of HX620W reviews out on the web, I'd like to offer you an HX520W review. The HX520W is Corsair's other power supply. The 520W little brother, if you will, of the 620W I reviewed a couple weeks ago.

     Why bother with a 520W when you could get the 620W? Price, of course! The 520W is significantly less expensive than the 620W, circulating for around the neighborhood of $119 as opposed to the HX620W's price of $169.

     The HX520W looks almost identical to the HX620W, except for all of the red stickers have been replaced with yellow stickers. I heard from a friend of mine that street races an Integra Type R that red is faster than yellow.

     Outside of appearance, we notice we're shorted a couple cables. We're missing one of the two-device peripheral Molex modular cables and one of the three-device SATA modular cables.

Type of connector: Corsair HX520W 
ATX connector 20+4
2 x 2 12V connectors 1
2 x 3 PCIe 2
8-pin Xeon/EPS connector 1
6-pin Xeon/AUX connector 0
5.25" Drive connectors 8**
3.5" Drive connectors 2*
SATA Drive power connectors 4
Fan only connectors (12V only) 2***
* The floppy power connectors are accomplished by using a Y-splitter off of one of the peripheral Molexes.
** Four of the 5.25" peripheral/drive Molexes are on two very short cables: 12" X 6" Ideal for optical drives.
The other six cables are longer 21" X 6" cables.
*** Fan only connectors are on a Y-splitter.

     Naturally, since this power supply is 100W shy of it's "big brother" we're going to see some lower ratings on the label...

Corsair HX520W
+3.3V +5V +12V1 +12V2 +12V3
-12V +5VSB
24A 24A 18A 18A 18A
0.8A 3A
Max Combined Watts 140W 480W 9.6W 15W

     According to this chart, based on the label on the unit itself, we have limiters on the 12V rails set to 18A each, but the total combined output of the 12V rails is only 480W (40A.) We see the 5V is brought down from 30A to 24A and the total combined for the 3.3V and 5V is now 140W instead of 170W.

 We shall tweak our load tests accordingly...

     Last time we tested a Corsair PSU, an assumption was made that the rails were split up like other 3 rail power supplies on the market: CPU on it's own rail to conform with ATX12V specs and the PCI-e connectors on their own rail so they can be loaded up to that rail's maximum capability.

     After the 620W was dissected following the publishing of the review, I found that one PCI-e connector was on one rail with two peripheral connectors while the other PCI-e connector was on another rail with the three peripheral connectors. Assuming that the PSU was following ATX12V specifications, I concluded that the CPU (via 4-pin +12V or 8-pin EPS+12V) was still on it's own rail and that the 12V leads on the ATX connector must be on the rail with the one PCI-e connector and two peripheral connectors.

     Now I come to find out, after looking closely at the PCB and speaking with individuals at Corsair, that the PSU actually DOES NOT follow ATX12V specifications and that I was wrong about the rail distribution AGAIN!

This is the front of the modular PCB as removed from the PSU housing.

On the back, we can see the traces and how the two different 12V leads go to the two different PCI-e connectors and the different peripheral connectors.

The "official" word from Corsair was the following:

  • 12V1: ATX 20+4, 4-pin +12V and 8-pin +12V
  • 12V2: PCI-e 1 and first two peripheral connectors
  • 12V3: PCI-e 2 and last three peripheral connectors

It gets better...

     Looking at the main PCB, we only see two points where 12V leads are soldered down. One labeled 12V1 and another labeled 12V2. For fun, I put a 30A load on the 8-pin EPS+12V connector. This should have tripped the PSU. It did not, which tells me that there is no OCP limiter set for this rail. I did the same with the ATX main connector and again the PSU did not trip.


Above is a close up shot of the PCB and where the 12V wires all solder down.

     This demonstrates that if the two rails are in fact separate, there is no OCP (over current protection) on each rail. Outside of a few traces zig zagging across PCB, I couldn't find how even 12V1 and 12V2 are separate, but I'm going to give Seasonic (the OEM for the Corsair units) the benefit of the doubt and say that we seem to have two 12V rails here, neither with any kind of "limit" on them.


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