- Joined
- Mar 12, 2002
The FX platform is the latest high performance offering from AMD, and while they can offer up quite a bit of performance they do come with some serious requirements. Id like to cover some of the essential bits of info you need to know in order to make the right choice for your new system.
A few things you need to ask yourself when selecting a motherboard are:
1: How many graphics cards do I plan to install
2: Do I have any special connectivity needs.
3: Am I planning to overclock the system.
4: How many cores do I need.
5: Aftermarket cooling options
Issue #1 and #2 go somewhat hand in hand. Todays latest and greatest GPUs require a high performance PCI-e slot. While x16 is there prefered opperation settling for and x8 slot will only impact your performance slightly, but you should shy away from using a x4 slot if at all possible. Other things to consider though are do you need a PCI slot? Are you using dual or triple slot GPUs? Do you need firewire/usb 3.0, or lots of SATA3.0 slots?
Issue #3 and #4 also have some common ground. More cores demand more from the motherboard supporting it, and overclocking even a 4 core FX chip will put a heavy demand on the motherboard in itself. If your considering overclocking your CPU and/or considering an FX 8XXX CPU you really want to put careful consideration into which board you select.
If you have no intention of overclocking your CPU ever(I mean this) then your choice in motherboards is alot wider. In this situation you simply want to verify that the CPU is on the motherboards supported list.
Issue #5 is a simple one, many motherboard manufacturers use a standard mounting dimensions for the chipset and VRM cooling. Gigabyte motherboard for example all use a standard set of holes for VRM and both chipset and as a result there are a wide variety of both air and water cooling options.
Ok now lets get onto the nitty gritty of it. Were going to discuss a few of the KEY FEATURES of a high quality motherboard.
Motherboard Chipset
At the time of this writing there are currently 3 AMD FX chipsets available the 970, 990x, and 990FX.
The 970 sports a total of 22 PCI-e 2.0 lanes split up as follows: 1 x16, 1 x4, and 2 x1 slots, and 4 dedicated between the northbridge and CPU. For users of a single GPU and few additional PCI/e devices this chipset likely offers everything you need.
The 990X carries a total of 22PCI-e 2.0 lanes split up into 1x16 or 2x8, 1 x4, and 2 x1 slots, and again we find 4 dedicated lanes between the CPU and NB. This is the lowest level chipset that is nVidia SLI capable, and therefore if you are considering SLI you cannot buy below this level.
The 990FX is rocking out with a total of 38 PCI-e 2.0 lanes. You get 2x16 or 1x16,2x8 or 4x8 slots, and of course you also get 1x4 and 2x1 slots depending on your particular motherboard's configuration.
Consider this as a general rule about motherboard chipsets. The higher up the chipset rank you go the better equipped the motherboard tends to be in general. While you may not need the features of a 990FX you will find that an entry level 990FX board SHOULD be better equipped than the average 970 motherboard, but as with everything there are some serious exceptions to this rule.
For the sake of completeness I want to mention that SOME older chipset motherboards are capable of supporting FX CPUS. If you can track down an 890FX based motherboard from the last generation with FX support BIOS it could potentially be as good as anything in the 990FX lineup.
However, there are a few current generation products built on top of older chipsets but are now considered low end parts and their price reflects that. In theory these boards will run an FX CPU but in my experience they are simply just to far down the spectrum to be worth using. I had one 770G based motherboard which was not able to run my CPU at stock speed without throttling.
VRM A.K.A the Voltage Regulation Module
The VRM is the circuit on the motherboard which supplies the required voltage to the CPU and memory. It is the heart of any motherboard and with the FX processors very high power demands it is ESSENTIAL to find a motherboard with a sufficient VRM.
The VRM is made up of a few layers of parts, and to make matters worse right now we are in the middle of a transition between the latest generation of analog VRM and the first generation of digital VRM systems. I am not going to get into the highly technical details of how these circuits do what they do, but we are going to spend a good bit of time covering what this circuit is, and how to pick one.
Things to know about VRM:
The VRM is made of of a bank of mosfets with a controller chip some chokes and a bank of filter capacitors. One mosfet, choke, and filter cap make up what we refer to as a "phase". More phases better distribute the load which permit a more stable stream of voltage, and increase the total theoretical power supply limit.
Digital VRMs have a faster response time and produce less heat for a given current draw. What this means to you is that if your highly overclocked 8 core chip goes from idle to full load the VRM will be able to jump the voltage from a nice power saving 0.9ish up to a sturdy 1.5+v faster than an analog system. Since they do not produce as much waste heat they require LESS cooling than an analog counterpart.
Analog VRMs can provide a smoother voltage when pushed to there absolute limits. The analog circuit WILL suffer from a larger margin of VDroop than a digital counter part, but when your pushing into highly unpredictable land the more stubborn nature of an analog VRM to just keep pumping out the high voltage can be a benefit, especially on CPUs that get really finicky past 4.2ISH ghz.
Mosfets have a very high thermal limit BUT when your asking a single mosfet to deliver 50+ amps at 1.4v you can expect that its going to get HOT, VERY HOT. Most lower end motherboards come equipped without VRM heatsinks. This is a clear indication that the motherboard is NOT well suited to overclocking or driving a high current CPU like one of the FX 6XXX or FX 8XXX series cpus.
To sum it up you want a MINIMUM of 6+2 digital or 8+2 analog phase VRM, and it MUST have atleast a passive heatsink. If your looking for very high clockspeeds consider 8+2 digital with PASSIVE COOLING OR 8+2/12+2 analong with ACTIVE COOLING. This bit of the motherboard is just as important as the PSU you connect to it, so take the time to find a board whos VRM is capable of meeting your needs. Here is a nice completish list list of motherboards and there VRM
Lets wrap it up with my personal list of approved AMD mobos at this time In order would be:
Closing Thoughts
There are alot of AM3+ motherboards out there, and with price ranging from $50 to $250. The above list shows that even if your a enthusiast overclocker that you still have a nice wide variety of price ranges to pick from. With the 970A-UD3 or the M5A97 EVO your looking at around $110 shipped. If you ask me this is a completely fair entry price point for an overclocking part.
The other thing you must be aware and this more or less belongs in the CPU section is the FX CPUs when overclocked can really put out some heat. Do not cheap out on your cooling solution, but it is not necessary to spend more than $50 on cooing if your not looking to shoot for the stars.
Notes
note1: This is my personal estimate of how far this motherboard can take a given CPU sample. IE if you have a CPU that will clock to 5Ghz max the listed board will be able to get you within that margin of the final OC. So lets say you have a CHV your going to get 4.95-5.0Ghz from this chip, while the M5A97 Evo would be stuck at around 4.6-4.7Ghz.
note2: All 3 of these gigabyte UD3 motherboards use the exact same VRM circuit design. The exact components used between models may vary.
note3: It has been brought to my attention that the Rev3.0 boards do not properly implement the APM disable option. While this could be fixed with a BIOS update it appears that Gigabyte is unlikely to do so. APM can have a major impact on your overclock by making you believe you are maintaining a higher overclock when in reality the board is throttling the CPU based on power load without your knowledge.
******UPDATE******
It appears that the UD3 Rev 4 boards are back on the menu. According to some testing done by bassnut these now support overclocking with APM disable working properly.
note4: This board has the potential to unleash your CPU unfortunately it appears that it is suffering from an unusually high rate of failure. Should you choose to purchase one of these you may find a gem or you may end up with a month or more of headaches RMAing boards trying to find a working unit. It appears that most major online etailers have stopped stocking this board due to the high number of RMAs. If you can find one for a good price it may be worth playing with, but I wouldnt take the gamble on my main rig.
A few things you need to ask yourself when selecting a motherboard are:
1: How many graphics cards do I plan to install
2: Do I have any special connectivity needs.
3: Am I planning to overclock the system.
4: How many cores do I need.
5: Aftermarket cooling options
Issue #1 and #2 go somewhat hand in hand. Todays latest and greatest GPUs require a high performance PCI-e slot. While x16 is there prefered opperation settling for and x8 slot will only impact your performance slightly, but you should shy away from using a x4 slot if at all possible. Other things to consider though are do you need a PCI slot? Are you using dual or triple slot GPUs? Do you need firewire/usb 3.0, or lots of SATA3.0 slots?
Issue #3 and #4 also have some common ground. More cores demand more from the motherboard supporting it, and overclocking even a 4 core FX chip will put a heavy demand on the motherboard in itself. If your considering overclocking your CPU and/or considering an FX 8XXX CPU you really want to put careful consideration into which board you select.
If you have no intention of overclocking your CPU ever(I mean this) then your choice in motherboards is alot wider. In this situation you simply want to verify that the CPU is on the motherboards supported list.
Issue #5 is a simple one, many motherboard manufacturers use a standard mounting dimensions for the chipset and VRM cooling. Gigabyte motherboard for example all use a standard set of holes for VRM and both chipset and as a result there are a wide variety of both air and water cooling options.
Ok now lets get onto the nitty gritty of it. Were going to discuss a few of the KEY FEATURES of a high quality motherboard.
Motherboard Chipset
At the time of this writing there are currently 3 AMD FX chipsets available the 970, 990x, and 990FX.
The 970 sports a total of 22 PCI-e 2.0 lanes split up as follows: 1 x16, 1 x4, and 2 x1 slots, and 4 dedicated between the northbridge and CPU. For users of a single GPU and few additional PCI/e devices this chipset likely offers everything you need.
The 990X carries a total of 22PCI-e 2.0 lanes split up into 1x16 or 2x8, 1 x4, and 2 x1 slots, and again we find 4 dedicated lanes between the CPU and NB. This is the lowest level chipset that is nVidia SLI capable, and therefore if you are considering SLI you cannot buy below this level.
The 990FX is rocking out with a total of 38 PCI-e 2.0 lanes. You get 2x16 or 1x16,2x8 or 4x8 slots, and of course you also get 1x4 and 2x1 slots depending on your particular motherboard's configuration.
Consider this as a general rule about motherboard chipsets. The higher up the chipset rank you go the better equipped the motherboard tends to be in general. While you may not need the features of a 990FX you will find that an entry level 990FX board SHOULD be better equipped than the average 970 motherboard, but as with everything there are some serious exceptions to this rule.
For the sake of completeness I want to mention that SOME older chipset motherboards are capable of supporting FX CPUS. If you can track down an 890FX based motherboard from the last generation with FX support BIOS it could potentially be as good as anything in the 990FX lineup.
However, there are a few current generation products built on top of older chipsets but are now considered low end parts and their price reflects that. In theory these boards will run an FX CPU but in my experience they are simply just to far down the spectrum to be worth using. I had one 770G based motherboard which was not able to run my CPU at stock speed without throttling.
VRM A.K.A the Voltage Regulation Module
The VRM is the circuit on the motherboard which supplies the required voltage to the CPU and memory. It is the heart of any motherboard and with the FX processors very high power demands it is ESSENTIAL to find a motherboard with a sufficient VRM.
The VRM is made up of a few layers of parts, and to make matters worse right now we are in the middle of a transition between the latest generation of analog VRM and the first generation of digital VRM systems. I am not going to get into the highly technical details of how these circuits do what they do, but we are going to spend a good bit of time covering what this circuit is, and how to pick one.
Things to know about VRM:
The VRM is made of of a bank of mosfets with a controller chip some chokes and a bank of filter capacitors. One mosfet, choke, and filter cap make up what we refer to as a "phase". More phases better distribute the load which permit a more stable stream of voltage, and increase the total theoretical power supply limit.
Digital VRMs have a faster response time and produce less heat for a given current draw. What this means to you is that if your highly overclocked 8 core chip goes from idle to full load the VRM will be able to jump the voltage from a nice power saving 0.9ish up to a sturdy 1.5+v faster than an analog system. Since they do not produce as much waste heat they require LESS cooling than an analog counterpart.
Analog VRMs can provide a smoother voltage when pushed to there absolute limits. The analog circuit WILL suffer from a larger margin of VDroop than a digital counter part, but when your pushing into highly unpredictable land the more stubborn nature of an analog VRM to just keep pumping out the high voltage can be a benefit, especially on CPUs that get really finicky past 4.2ISH ghz.
Mosfets have a very high thermal limit BUT when your asking a single mosfet to deliver 50+ amps at 1.4v you can expect that its going to get HOT, VERY HOT. Most lower end motherboards come equipped without VRM heatsinks. This is a clear indication that the motherboard is NOT well suited to overclocking or driving a high current CPU like one of the FX 6XXX or FX 8XXX series cpus.
To sum it up you want a MINIMUM of 6+2 digital or 8+2 analog phase VRM, and it MUST have atleast a passive heatsink. If your looking for very high clockspeeds consider 8+2 digital with PASSIVE COOLING OR 8+2/12+2 analong with ACTIVE COOLING. This bit of the motherboard is just as important as the PSU you connect to it, so take the time to find a board whos VRM is capable of meeting your needs. Here is a nice completish list list of motherboards and there VRM
Lets wrap it up with my personal list of approved AMD mobos at this time In order would be:
Code:
Motherboard % overclock *note1
Asus Crosshair V formula/z 99-100%
Asus Sabertooth R2.0 Gen 3*note4 99-100%
Asrock Fata1ity 990FX 99-100%
Asrock 990FX Ext9 99-100%
Asus Sabertooth R2.0 and Asus Sabertooth 990FX 97-99%
Gigabyte 990FX UD5 or UD7 97-99%
Asus M5A99X Evo or M5A99FX pro 95-97%
Gigabyte 970, 990X, 990FX UD3*note2/3 95-97%
Asus M5A97 Evo or any MSI 990(X/FX) 94-95%Closing Thoughts
There are alot of AM3+ motherboards out there, and with price ranging from $50 to $250. The above list shows that even if your a enthusiast overclocker that you still have a nice wide variety of price ranges to pick from. With the 970A-UD3 or the M5A97 EVO your looking at around $110 shipped. If you ask me this is a completely fair entry price point for an overclocking part.
The other thing you must be aware and this more or less belongs in the CPU section is the FX CPUs when overclocked can really put out some heat. Do not cheap out on your cooling solution, but it is not necessary to spend more than $50 on cooing if your not looking to shoot for the stars.
Notes
note1: This is my personal estimate of how far this motherboard can take a given CPU sample. IE if you have a CPU that will clock to 5Ghz max the listed board will be able to get you within that margin of the final OC. So lets say you have a CHV your going to get 4.95-5.0Ghz from this chip, while the M5A97 Evo would be stuck at around 4.6-4.7Ghz.
note2: All 3 of these gigabyte UD3 motherboards use the exact same VRM circuit design. The exact components used between models may vary.
note3: It has been brought to my attention that the Rev3.0 boards do not properly implement the APM disable option. While this could be fixed with a BIOS update it appears that Gigabyte is unlikely to do so. APM can have a major impact on your overclock by making you believe you are maintaining a higher overclock when in reality the board is throttling the CPU based on power load without your knowledge.
******UPDATE******
It appears that the UD3 Rev 4 boards are back on the menu. According to some testing done by bassnut these now support overclocking with APM disable working properly.
note4: This board has the potential to unleash your CPU unfortunately it appears that it is suffering from an unusually high rate of failure. Should you choose to purchase one of these you may find a gem or you may end up with a month or more of headaches RMAing boards trying to find a working unit. It appears that most major online etailers have stopped stocking this board due to the high number of RMAs. If you can find one for a good price it may be worth playing with, but I wouldnt take the gamble on my main rig.
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Might help save some people a headache.
if there's a weak component on the board chances are it will pop no matter what load. Best to crank it up and see how it copes 
