Heatsinks on flash controllers aren't a new concept, but it's becoming a novelty on small form factor SSDs using the M.2 form factor.
You should think of the flash controller like a processor, the main component in your PC. SSD controllers are intelligent and have to process more data than most realize. Those calculations require switching and power, so they produce heat just like your CPU and GPU, two components that we associate with heat sinks used for cooling.
Like other processors, newer SSD controllers use progressively smaller lithography nodes to decrease costs and increase efficiency. Western Digital has kept a tight lid on it's custom flash controller's architecture, but we suspect it uses a 28nm process node similar to the Phison PS5012-E12.
The 28nm node is a significant improvement over the 55nm node used on controllers like the Phison PS5007-E7. The E7 generates quite a bit of heat. The controller could idle in the high 40-Celsius range. The WD Black SN750 idles at 35-Celsius, and the heat sink model lowers the idle temperature to just 28-Celsius.
Most companies configure thermal throttling on a curve. The less obtrusive throttle usually kicks in around 75-Celsius. Some drives use a mid-throttle in the low 80-Celsius range and a severe, self-preserving at 85-Celsius. Every company uses different settings and techniques, so the values change. They can even change from one firmware revision to another.
To discuss how a heat sink helps users we first must pick a number where the controller decreases IO performance to reduce the temperature. We will just use 80-Celsius as the throttle point. With that set, we can look at the idle temperatures, 28 and 35-Celsius.
Right off the bat, the heat sink SSD gives users more headroom before engaging the thermal throttle feature. That's not the most important or even impactful effect. The heat sink first absorbs heat from the controller and then increases the surface area for the heat to dissipate compared to the bare controller.
This reduces the time it takes to reach a thermal throttle condition; it can even eliminate it if there is sufficient airflow. Using a hypothetical number, let's say the bare controller throttles after writing 200GB of data. The heat sink could extend the data writes to 500GB or more before throttling.
The WD Black SN750 now ships in both versions, the naked M.2 2280 form factor SSD we tested in January and the new version with an EK designed heat sink. The heat sink version we're testing today was announced with the original Black SN750, but shipping didn't begin until last month.
The heat sink series ships in three of the four overall capacities, 500GB to 2TB. The 250GB Black SN750 doesn't have a SKU with the heat sink. At the time of writing, the 500GB and 1TB heat sink models were on Amazon and Western Digital's own website for sale. The massive 2TB was not available, yet.
The performance specifications are the same as the non-heat sink versions we previously tested. The performance benefits of having a heat sink to cool the controller falls into the gray area not found on the specifications sheet.
In the chart above, we wrote 128KB block data to both 1TB Black SN750 SSDs. The orange bar show the amount of data written in ten minutes at queue depth 1. The Black SN750 with a heat sink wrote just over 44 gigabytes more than the non-heat sink version. The average megabyte per second increase (red bars at the bottom) was 168 MB/s.
Pricing, Warranty, and Endurance
WD released the Black SN750 heat sink SSDs at the same MSRP as the non-heat sink drives. SSD prices have dropped considerably since we tested the non-heat sink SN750. The 1TB drive we're testing today currently sells for $249.99, exactly where the non-heat sink was in January. The non-heat sink 1TB drive now sells for $228.56 at Amazon. You don't have to pay a lot for the heat sink upgrade, but the Black SN750 but this series sells in the same range as the Samsung 970 EVO Plus ($247.99 Amazon). That's around $100 more than the 960GB MyDigitalSSD BPX Pro ($149.99 Amazon).
When WD rolled out the new Black SN750, the company also unveiled a new Dashboard software. When the software detects a SN750, it gives users the option of enabling Game Mode.
The Game Mode feature disables the lower power states of the Black SN750. This reduces latency and increases what we call the user experience. SSDs will move into a lower power state to reduce power consumption. There are several power states but not every company uses them all.
The latency comes from the time it takes to turn everything back on. If you have soft lighting in your home or car, you can use that as a reference. In this case, you turn the power and over a split second, the light comes on with a slight transition between off and full light. This happens much faster with an NVMe SSD but any delay or transition state adds latency. Game Mode eliminates the transition because it keeps the drive ready to move data at high speeds.
A Closer Look
The EK heat sink looks great on the Black SN750. In our testing, it dropped the idle temperature around 7 degrees at idle, and we never reached the highest throttle temperature (80 degrees) in our testing.