LAB501

Clash of the Titans VGA 2014 – ASUS Geforce GTX 780 Ti DirectCU II vs ASUS Radeon R9 290X DirectCU II

VRM analysis

Asus R9 290X DC2

1

2

3

4

5

6

The GPU voltage regulator module is build with 6 x 60 amps phases (Dr.Mos IOR 3550M mosfets), “Super Alloy” chokes and polymeric/ceramic capacitors. The VRM is controlled by an ASP 1300 PWM. The memory VRM is very robust as well and employs two phases, each of them is composed by 3 Low RDS(on) mosftets and polymeric/ceramic capacitors.

PLL VRM is per phase identical to the memory VRM, is built with one phase and the only difference is the use of tantalum capacitors instead of the polymeric ones.

Although I would have preferred the let’s call it “classic” 8 phase DC2 VRM (that has shown its strengths time and time again), this VRM is very solid as well and put up quite well with extreme testing under air and water cooling. But stability and load-line calibration attributes where not as good as with the previous DC2 VGA cards, as you can clearly see below:

VRM TEST (loadline + stability)

~20mv idle load difference and ~ 20mv load variation is far from the best I’ve seen.

Asus GTX 780 Ti DC2

P1350804

P1350807

P1350810

I was pleased to see the old DC2 design used on this board, especially the 8-phase GPU VRM and the 2-phase memory VRM. Each phase is built with three low impedance MOSFETs, a “Super Alloy” choke and ceramic/polymeric capacitors, and is controlled by Asus’ PWM IC. The GPU also benefits from additional filtration provided by the tantalum capacitors placed on the back of the PCB.

Load-line calibration tests and stability tests reveald a situation worse than of the the 290X, more precisely a difference between idle and load of 34mv and a 21mv variation during load.

VRM TEST (load-line + stability)

This are not particularly good results, I’ll let you check out the stability test we subjected the 7970 DC2 to, to see what millivolt level stability means.

HD 7970 DC2 VRM TEST

A wide voltage variation during load will definitely affect stability, so I am not happy at all with the shortcomings we see here. It is quite clear by know that this not is progress., but regression. Still, with a little interest from ASUS this problems can easily be fixed.

Voltmod

mod 780

P1350740

P1350743

Leave a Reply