Advice on FX8120

[RGone]

My gawd when will this Bulldozer/Zambezi thing ever end? Heat heat heat, everywhere you turn. Caddi Daddi has raising capacitors on his motherboard from 1.6+ Vcore on a power hungry BD. Questions of can I get enough VRM circuitry and cooling to push a BD. That is a funny statement I just typed. To me anyway. Did anyone ever try to 'push' a bulldozer. In real life pushing a bulldozer would be a 'heavy' job for sure. So to in computer land to push the clocks of a BD processor with its' high heat and power draw when removed from its' designed power control parameters.

I sincerely hope for the consumer's sake that PD is less hungry for energy and then should need less cooling to remove the heat from that energy consumption.

The problem we all are facing is when a user wants informational help in specc'ing out a system. That specc'ing is even more of a complicated task of trade-offs if there is a tight budget and we want to purchase enough VRMs and cooling of that power circuit at the outset. That costs money. We are all 'beginning' to believe in VRM phases due to the power hungry nature of BD. We did not know this at first for extended periods of use. We believe we know it now.

My recommendation to the OP would be to NOT buy BD at all. Wait for PD processors since they are being hyped as faster performing and less power hungry. Stick AMD with all those HOT FX processors like they screwed us by drying up all the good 1090T and 1100T processors so we HAD to buy the FX series of processor. Maybe teach big business a minor lesson. I digess. Crap am sorry.

If one has to buy FX-series before the PD processors arise and also intends to run with the power controls turned off then buy the best proven VRM circuit you can buy and that includes good power phases and cooling. I think over the long term course of time, that we may see boards fail from pushing power and heat for BD. Warranty time frame may become a topic in a year or two. i know some boards have a 5 year warranty and for those that do not upgrade often, that might be a consideration with an always pushed BD not running in BD's designed power parameters.

Yes, I know I am typing some stuff that is perhaps not considered yet, but I think it maybe time to look at the bigger picture for out reccomends. Well just maybe.

At any rate I am still RGone...ster. To my place.

 

[Bobnova]

Remember for computational analysis that you will only get the full benefit of the Bulldozer if you're performing integer calculations. FLOP will perform as if it was a quad core.

This may be the most crucial post in this thread.
If the program uses floating point stuff a Thuban will be faster.
If it is pure integer math and heavily threaded, the BD will be in its element and will stomp pretty much anything.

On motherboards: For BD you absolutely positively need a heatsink on all MOSFETs near the CPU socket.

On phases: There are two things that are called a "phase" in the VRM world.
There is the marketing definition, where a "phase" is a MOSFET/MOSFET/inductor group, regardless of how it is wired/driven.
Then there is a "phase" in the larger EE/electronics world, which is a MOSFET/MOSFET/inductor group that is driven out of phase with the other groups.
An Ascii example follows, please note that the end results are not a square of course, ascii has it's limitations. First, an example with three marketing type phases:

Phase1 output: _____/-------\_______/---------
Phase2 output: _____/-------\_______/---------
Phase3 output: _____/-------\_______/---------

Overall voltage output: _____/-------\_______/---------

Next, with three "real" phases. I call 'em EE phases.
Phase1 output: -----\_______/--------\_______/-------
Phase2 output: ___/-------\_______/---------\_______/
Phase3 output: ________/-------\_______/---------\__

Overall voltage output: ---------------------------------------


Now obviously this is a Made For TV drama, but that is the difference between real phases and marketing phases.
The crucial thing is, very few voltage controllers can control more than six real phases! If you look around you you'll find that most motherboards and video cards have "phases" multiples of 6. If you want to know how many EE phases there are you can look for the MOSFET drivers. They're typically ~0.25" square jobs on the bottom of the board that have a lot of pins that just barely stick out from the package on all sides. Not to be confused with the rectangular characters with four pins that barely stick out on each end, those are MOSFETs.
An excellent example is the 5870 lightning. "12" phases, 6 MOSFET drivers.
http://www.techpowerup.com/reviews/MSI/R5870_HD_5870_Lightning/3.html

More EE phases mean smoother power. More phases of any kind mean more peak current output is possible, as the MOSFET/MOSFET/inductor groups are the limiting point for current flow.

 

[trents]

Thanks for the technical insight, Bobnova. By "bottom" of the board do you mean the underside or the bottom edge? Could you circle the mosfet drivers for us in an attached pic from that link you provided?

 

[Bobnova]

Back side, here are some pics. First of the front side with a marketing phase (also a phase from the sense of current capacity) circled (with a square...).




Now the rear of the board with a MOSFET driver circled. Note six drivers and 12 marketing phases. If you have the card in front of you there are traces you can look for, but the drivers are the easiest.
Do note that on some motherboards some of the drivers are under the MOSFET heatsink and some controllers (lower phase count controllers) have drivers built into them, so this isn't always accurate. There are no controllers I am aware of with more than eight output channels however.


Thanks to TPU for the nice clear photos.

 

[RGone]

A motherboard for reference...

The pictures linked below are taken from a Bit-tech review of P755D Deluxe motherboard. High Definition pics of the rear of a mobo a hard to find. http://www.bit-tech.net/hardware/motherboards/2009/09/09/asus-p7p55d-deluxe/3

Highlighting is theirs not mine. Thanks to BTech.

The first pic is of Asus's Advertising Cpu phase layout on top of the motherboard.




This second pic of is the rear of board and Asus Adv. phase drivers.

 

[Bobnova]

That's a remarkable number of drivers!
Something else that has been done in the past by Gigabyte in the P55 era with their "24 phase!" bits is to use phase doublers, they double the outputs to the drivers at the cost of cutting the switching frequency in half. The gigabyte P55-UD29835 had "24" phases with all the smoothness of 6 phases

In any case, Asus appears to be being more honest then usual there.

 

[caddi daddi]

ok so i am looking for a new board, asus crosshair v, and the asrock fatality pro.
#1 what do power phases mean to me?
#2 how do i identify good power phaseing?
#3 what is meant by the terms 8+2 power phaseing and i think i saw 1 that said 12+2 power phaseing?

 

[caddi daddi]

hhhhhhhmmmmmmmmmmm, your on to something here. in my 8 core or 6 core thread i have just run the sim that i run on my 8 core with a thuban, and it ran the sim in a time very much closer to my 955 than to my fx. yet owners of thubans show a much higher glop number running intel burn test than any of my 4 fx 8120's can approach.....
tells me that for processors, it all depends on what you are doing with it, and i have also found that out and out clock spped means little in the day to day use.