Do I Have Enough Wattage?

[Christopher Sadlowski]

Alright guys and gals, I need a little bit of advice. So, I just purchased new components to rebuild by PC that, uh, well let's just say divorce and electronics don't mix well. Some components I was able to salvage, including the DVD drive, the PSU, and maybe the hard drive, but I'm still waiting for the last few components to arrive (WHY is the motherboard the last to arrive; it's not the most critical component, you know? :/ ). The PSU is a 650 watt Corsair and I'm not sure if it's got enough juice to run the new PC. I purchased the new AMD Rx line, specifically the Rx 470 by XFX and the documentation suggests at most a 550 watt PSU. I'm (and don't laugh! I tend to use "last years tech" anyway because I have to be very conscious of my budget) using an AMD FX-8300 95 watt CPU, an MSI Krait Edition SLI blablabla AM3+ Socket motherboard, 16 GBs of DDR3 Corsair Vengeance RAM across 4 sticks, a Western Digital Green 2TB HDD, and I think that's probably enough info for you all to help me out. If I use just the posted wattage as a guide, 550 watts for the PSU and another 95 watts for the CPU, that only leaves me with an overhead of 5 watts if I use a 650 watt power unit. That doesn't also take into account the power requirements of the RAM and other components. I know the old 28nm architecture of the CPU is going to need more power to run and is a little less efficient than the new 14nm manufacturing process for the GPU which requires much less electricity. I also overclock, but I use software for it (typically what comes with the mobo and I fiddle around with the driver software from AMD to get my GPU clocks stable). So, am I really and truly cutting it too close with the max wattage of my PSU? I read a few posts of people running a comparable build as what I'm about to put together and they said they were running as low as 450 watts and everything was fine, but I'd appreciate a little input from the community to make sure I'm not setting up a build that simply won't turn on because not enough electricity is available.

 

[weberdarren97]

You're running a single CPU and an RX 470 on a 650W unit. That's plenty enough wattage.

The graphics card says that it wants 550W, but that's not how much power it will actually draw. Due to the fact that different manufacturers of power supplies have different ways determining where power goes, AMD can't always guarantee that there will be the necessary connectors on units under 550W. Hence the 550W recommendation.

 

[weberdarren97]

Typical board power of an RX 470: about 120 watts. That's including power draw from the PCIe slot and PCIe power connectors.

https://www.amd.com/en-gb/products/graphics/radeon-rx-series/radeon-rx-470

 

[Calvin7]

The FX-8300 has a TDP (Thermal Design Power) of 95 watts.

The Thermal Design Power (TDP) is the average maximum power a processor can dissipate while running commercially available software. TDP is primarily used as a guideline for manufacturers of thermal solutions (heatsinks/fans, etc) which tells them how much heat their solution should dissipate.

XFX Radeon RX 470 Series graphics card
Requirements

External Power - 6-pins : 1
Minimum Power Supply Requirement : 500 watt
XFX Recommended Power Supply : XFX 550W PSU

 

[weberdarren97]

I estimate that OP's machine will draw less than 400 watts when under load.

 

[Christopher Sadlowski]

You're running a single CPU and an RX 470 on a 650W unit. That's plenty enough wattage.

The graphics card says that it wants 550W, but that's not how much power it will actually draw. Due to the fact that different manufacturers of power supplies have different ways determining where power goes, AMD can't always guarantee that there will be the necessary connectors on units under 550W. Hence the 550W recommendation.

Wow, thanks for the quick reply! I can rest easy knowing I don't have to go through the hassle of an RMA. So I guess the other folks running similar builds were correct and legitimately running 450W PSUs. I just found it unbelievable; it just seemed so...low. I know that high-output PSUs (like 1,000W or so) are pretty pointless for a typical gaming machine, but knowing that low power requirements are the real deal I can proceed with putting everything together with confidence that it won't say, "HAHA, f**k you with this pitiful power supply!" I always leave room for a second GPU and I just never proceed with running CrossFire as my machines tend to last a really long time and I never find a need for that second card as I'm not a fanatic of getting outrageous framerates and whatnot. I wish these damn companies put these specifications in a prominent spot so I don't have to waste everyone's time asking these noobish questions. Thanks a ton @weberdarren97, you've saved me a bi headache!

 

[weberdarren97]

What you can do if you're not sure about a video card's power draw is just look at the connectors it has on it.

A graphics card can draw up to 75 watts from the PCIe slot. It can also draw up to 75 watts from a 6-pin PCIe power connector and up to 150 watts from an 8-pin PCIe power connector. If you add together the total possible amount of wattage from the power connectors then add 75 watts from the motherboard, you'll have the maximum amount of power the card can draw. No cards actually draw as much power as their connectors provide unless you get a modified card BIOS that allows you to raise the power limit to not so sane levels. These "hacked" BIOS's are usually used for liquid hydrogen overclocking... Not usually to run games, but simply to break world records.

 

[Christopher Sadlowski]

What you can do if you're not sure about a video card's power draw is just look at the connectors it has on it.

A graphics card can draw up to 75 watts from the PCIe slot. It can also draw up to 75 watts from a 6-pin PCIe power connector and up to 150 watts from an 8-pin PCIe power connector. If you add together the total possible amount of wattage from the power connectors then add 75 watts from the motherboard, you'll have the maximum amount of power the card can draw. No cards actually draw as much power as their connectors provide unless you get a modified card BIOS that allows you to raise the power limit to not so sane levels. These "hacked" BIOS's are usually used for liquid hydrogen overclocking... Not usually to run games, but simply to break world records.

Ah, thanks for that little bit of information! This will surely come in handy in the future. I won't have to waste anyone's time again! You know, funny you should mention GPU mainboard BIOSes, I always wondered whether or not those could be updated much like those for the motherboard; I always see the BIOA version listed for my GPU but I've never gone on a hunt to gather information about whether or not they can or should be updated. I overclock, but I don't have any liquid nitrogen tanks laying around to use in a thermal loop for my GPU. Oh well, no world records for me.
Oh, and the PC works great so your advice was certainly helpful. The only hiccup I'm dealing with is some networking issues but I'm seeking advice for that on another thread. It never fails, there's always SOMETHING that gets snagged when I put together a new rig. At least this time it wasn't two DOA hard drives like the last build I assembled.