What you need to know about AM4

Please also read our Ryzen CPU FAQ here

  AM4 is a different socket to previous generations, and the cooler mounting back plate has changed as well.  The plastic retainer clips which fit a plethora of aftermarket coolers still work, but if you want to reuse an AM2-3 cooler model which replaces the back plate you may need to upgrade to a new cooler, or get an adapter kit.  Many manufacturers offer a free adapter kit for their existing models to fit on the new AM4 platform, and HTPCX will endeavor to source all of the most common ones to have at the ready.

  Ryzen CPUs do not have integrated graphics, and video ports on motherboard with a Ryzen chip will be inactive.  The AM4 motherboards with video ports are for the upcoming AMD APU line, which features integrated graphics.  Buying a motherboard with video outputs will not make it inherently slower with Ryzen than a motherboard without, but will allow you to swap to a APU in the future if you choose.  The AM4 platform will continue to 2020 and it is speculated that the new AM4 APUs may be able to take further advantage of CrossFireX graphics than Ryzen in the future, however the Ryzen CPUs will continue to be more powerful in multi-threaded computing.


  Ryzen processors are very new.  Motherboard manufacturers tried to have many models ready for release day, but not all of the CPUs were released at once.  This means BIOS updates may be necessary in order to boot with a newer CPU.  Updating the BIOS can result in permanent failure if the system is not stable during the update.  Many reports of failures have come from people who did not use compatible RAM, or tried to update the BIOS with an unstable overclock.  If you will be buying a motherboard which may have BIOS version that does not support the CPU you have chosen, send us a message and we can verify or update the BIOS before sending it to you.  Updating the BIOS and Windows both is very important with this new processor.  Two noteworthy improvements over release day are drastically increased maximum RAM speeds, and a significant improvement in FPS while gaming.

  One of the primary complaints upon release was the clock speeds of DDR4 memory modules on the AM4 platform.  The problem was that even RAM which was rated to OverClock up to 3200OC* was running at 2400MHz.  This is largely fixed on most motherboards by installing the latest BIOS, which should include (at time of writing) AGESA 1.0.0.6. which allows RAM speeds up to 4000MHz.  Updating the BIOS should be done only when the system is stable, which may require reducing RAM speed during the update.  However, trying to exceed 2667MHz with Ryzen is overclocking and not guaranteed to work, with any motherboard or RAM configuration.  
Officially, Ryzen supported RAM speeds are:

Dual Channel

Single Rank

2x DIMM

2667MHz

Dual Channel

Dual Rank

2x DIMM

2400MHz

Dual Channel

Single Rank

4x DIMM

2133MHz

Dual Channel

Dual Rank

4x DIMM

1866MHz

  It is mention worthy that the performance difference in RAM between 2667MHz and 3200MHz is roughly 1%.  And as always, damage attributed to overclocking is not covered by any warranty.

  While Nvidia SLi is only supported on x370 motherboards, AMD Crossfire is available on many B350 models.

  Ryzen chips have 24 direct-to-CPU PCI-e lanes.  Of those 24, 16 lanes are dedicated to GPU use.  Regardless of how many PCIe x16 ports your motherboard has, a 2way Sli or CrossFireX will be running at PCI-e x8 for each card.  It is mention worthy that even with the most powerful video cards, the performance difference between x8 and x16 lanes on PCI-e 3.0 is less than 5%, which is less than the performance-per-card lost when enabling SLi or CrossfireX.

  Those 24 lanes add up.  Some motherboard offer up to 2 m.2 NVMe interfaces directly on the motherboard, but sacrifice a set of SATA ports when both are in use.  Please check the motherboard specifications if you have elaborate storage needs. 

  Picking the right board for your needs is easy if you read key differences below.  Overclocking to extremes however becomes hazardous to your components if you do not pay attention to the MOSFETs.  With insufficient power phases or cooling, the MOSFETS may overheat when overclocking on high core count processors or high frequency.  Each motherboard, regardless of chipset, may have different power phase specifications; if you are looking for a reliable overclocking board be sure to check the power phase info for the specific model.  In brief, more MOSFETs and more power phases make less heat.  Remember, liquid cooling the CPU reduces airflow over the MOSFETs.

  It's not specific to AM4, but many motherboards are advertising high phase count, when in actuality they are adding additional MOSFETs to the same phase.  This does increase capacity, but be aware that phase marketing by manufacturers can be misleading.

  AMD recommends staying below 1.42V on the Ryzen architecture.

A300:  Intended for small form factor miniITX builds, the A300s is similar to the A320 below.  Raid configurations are limited to 0, 1.

X300:  Intended for small form factor miniITX builds, the X300 is an enthusiast level chipset which supports overclocking as well as SLi and CrossFireX.  AMD recommends high end cooling for overclocking on this chipset.  Raid configurations are limited to 0, 1.

A320:  Intended for budget systems, the A320 chipset is the entry level board to AM4.  It lacks overclocking, SLi and CrossfireX, and a few interfaces shown in the graphs below.  It can however offer support for the full line of AM4 processors, and those who don't need the additional features can appreciate the factory comforts of a fully compatible system at an affordable price.

B350:  The best of both worlds, the B350 offers virtually every feature of the highest-end X370 motherboards at a lower price.  While fully capable of overclocking, the B350 does not have Nvidia SLi support.  Many models do support CrossFireX though, as well as many of the overclocking features the X370 has.  Among the interface trade offs shown below, the B350 gains 2 more PCI-e lanes and a 10GBps USB 3.1 port over the A320 models.

X370:  Socket AM4s elite chipset, X370 motherboards boast all of the features the CPU can muster.  A plethora of interfaces and options open up, including Nvidia's Quad SLi capability.  This may be its most important feature, as some of the best B350 motherboards offer everything else, though in reduced quantities.  See the chart below.

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