Apologies in advance for the long post!
Many of the latest Mini-ITX boards now include an M.2 slot on the underside of the board. These drives offer many advantages over conventional storage drives such as reduced component space inside the case and vastly increased data transfer speeds.
Those are the positives, now onto the negatives:
There seems to be allot of talk about how well these drives will perform in cramped and hot cases with reduced airflow, with concern for throttling and reliability. M.2 drives are known to run hot and their massive transfer rates causes drive temperatures to rapidly rise even further.
I have carried out a series of testing in the LZ7 to try and see whether throttling is a real issue, and also whether storage maximum performance can be maintained under heavy load stress conditions.
The test system being used:
SYSTEM SPEC
LZ7 Case
140mm Prolimatech Case Fan
Corsair SF450 PSU
Gigabyte B150N Pheonix-Wifi motherboard
Intel i5-6500
Noctua NH-L9i
8Gb Dual Channel 2133Mhz DDR4 RAM
Gigabyte GTX 960 4G OC
STORAGE DRIVE
Samsung PM951 256Gb M.2 PCIe SSD
Claimed Sequential Read/Write = 1000/280 (MB/s)
TEST SETUP
The PM951 SSD was benchmarked under various system conditions, including:
Each test state allowed the system and drive temperatures to settle before benchmarking was carried out.
Temperatures of the PM951 were recorded under each condition at idle drive state and also the maximum drive temp recorded during the CrystalDiskMark benchmarking test. The sequential read speed was recorded from each test to determine how much (if any) the drive throttled.
RESULTS
OBSERVATIONS
IDLE SYSTEM STATE
Straight away you can see that the PM951 exceeds its claimed sequential read speed by around 50% under normal conditions reaching a massive 1,576MB/s. Great stuff!
During the testing it was observed that throttling occurs in 2 steps, the first step is when the drive hits 70C, the PM951 throttles down to 315MB/s, around one third of its claimed 1000MB/s rating. The second step occurs at 75C where the drive takes a massive dip down to just 71MB/s. it may drop further above 80C but the drive never exceeded this temp.
Focusing on the M.2 Idle temps, you can see that without any active case cooling (0 rpm case fan) the M.2 Drive sits at around 60C when the system is completely idle. This is a worrying temperature sitting just 10C below its throttle temp without any effort.
Activating the system fan to 50% speed reduces the M.2 idle temp down by around 10C, taking the fan up to 100% brings it down a further 10C sitting at a more comfortable 38C.
Running the CrystalDiskmark test caused the PM951 to reach 72C and throttle to 315MB/s without any active cooling, it took less than a minute to pass 70C. With the case fan set to 100% the PM951 reached 59C maximum and maintained its full performance.
Now for the interesting part, covering the vents had the opposite effect to what I was expecting, the PM951 drive temperatures actually reduced in both idle and benchmarking conditions in the region of 5C - 10C. I will talk more about this later.
FULL SYSTEM STRESS STATE
Whilst the system is being put under heavy load and without any active case cooling the system temperature reaches a toasty 57C, the noctua NH-L9i is also nearly flat out trying to keep the CPU under control. Under these conditions the PM951 drive sits at a disturbing idle temperature of 67C, just 3C lower than its throttle point. As soon as the CrystalDisk benchmark is started the drive hits 70C and throttles, and within a minute the drive hits its 75C limit resulting in a read speed of just 71MB/s and maxing out at 80C by the end of the test.
A system case fan speed set to 50% (753 rpm) brings the drive temperature down by 10C during disk benchmarking, but it still experiences some throttling achieving a read speed of 607MB/s.
Taking the fan speed up to 100% (1072 rpm) reduces the idle drive temp by around 10C but doesn't bring the benchmark temperature down below 70C, however it does allow the drive to achieve almost full performance during the disk benchmarking at 1515MB/s.
Again, covering the underside vents up has a positive effect on M.2 drive temperatures, this is completely unexpected and will be discussed in the next section.
UNDER SIDE VENTS
The bottom panel of the LZ7 has a series of vents under the motherboard, the intention of these vents is to allow hot positive pressure air to escape out and apply a cooling effect to M.2 drives mounted on the underside of a motherboard.
However, from the testing carried out so far, it has been observed that covering up vents actually results in lower M.2 drive temperatures in almost all conditions. This is the complete opposite of what was expected.
I have put some serious thought into why this could be, and I think there are 2 possible reasons both of which may be contributing:
REASON 1
On the Gigabyte B150N board, the M.2 Drive is located along the edge near to the GPU which is the opposite side of the board to the case fan. The underside vents sit in between the fan and the drive, it is very possible that the fresh cool air from the case fan is escaping through the vents before it reaches the drive.
Covering the vents forces the cool air from the fan to instead travel all the way along the underside of the motherboard so it reaches the M.2 Drive, the air cools the drive and the heat is then carried toward the GPU side and exits the case.
A possible improvement to the design would be to remove the 'square' vent arrangement (middle of the picture above), and instead increase the width of the GPU underside vents (seen on the left of the picture above).
This theory explains the large difference in temperatures when the fan is running for open and closed vents.
REASON 2
The GPU vents directly out the bottom of the case, it is possible that some of this heat will make its way under the case and travel towards the middle vents, this hot air may be seeping upwards back into the case through the vents and contributing to the M.2 drive temperature. Covering the vents may be preventing this re-circulation from happening.
This theory explains why there is a small difference in temps when the case fan is switched off between open and closed vents.
CONCLUSION
Hopefully your still with me, sorry for the long post!
Without any active case cooling the M.2 PCIe PM951 SSD idles at around 60C with a system temp in the high 40's, this temperature rises to around 67C when the system is put under heavy load. With a throttle temp of 70C it doesn't take much storage activity before throttling occurs with read speeds dropping from 1576MB/s to 315MB/s in a low loaded system and as low as 71MB/s in a heavy loaded system.
Add in some active case cooling and the M.2 drive temperatures reduce to a more acceptable level and are able to sustain their full performance for much longer periods.
Under normal system usage with some level of active case cooling I don't expect that an M.2 PCIe drive will throttle unless you are transferring some really large files one after another.
However, a couple of hours of gaming with higher system temps the PM951 PCIe SSD does begin to struggle, even with good case cooling and ventilation the drive can hit its throttle temp very quickly during sequential reading.
Part of the reason for these high temperatures are that the drives are tucked away under the motherboard and shielded from most of the direct the case cooling. Directing airflow under the motherboard is intended to help with this.
Testing has shown that airflow under the motherboard is key to maintaining full drive performance and vent position play a part in directing the airflow, therefore a small design change will be made to the underside ventilation layout to improve M.2 Drive thermal performance.
*EDIT:
I forgot to mention that this testing was done in 25C ambient thanks to a brief encounter with something called a 'summer' in the UK.
Many of the latest Mini-ITX boards now include an M.2 slot on the underside of the board. These drives offer many advantages over conventional storage drives such as reduced component space inside the case and vastly increased data transfer speeds.
Those are the positives, now onto the negatives:
There seems to be allot of talk about how well these drives will perform in cramped and hot cases with reduced airflow, with concern for throttling and reliability. M.2 drives are known to run hot and their massive transfer rates causes drive temperatures to rapidly rise even further.
I have carried out a series of testing in the LZ7 to try and see whether throttling is a real issue, and also whether storage maximum performance can be maintained under heavy load stress conditions.
The test system being used:
SYSTEM SPEC
LZ7 Case
140mm Prolimatech Case Fan
Corsair SF450 PSU
Gigabyte B150N Pheonix-Wifi motherboard
Intel i5-6500
Noctua NH-L9i
8Gb Dual Channel 2133Mhz DDR4 RAM
Gigabyte GTX 960 4G OC
STORAGE DRIVE
Samsung PM951 256Gb M.2 PCIe SSD
Claimed Sequential Read/Write = 1000/280 (MB/s)
TEST SETUP
The PM951 SSD was benchmarked under various system conditions, including:
- Idle system
- Heavy load system (Simultaneous Prime 95 + Unigine Valley)
- Various case fan speeds (0%, 50% and 100% speed)
- Underside vents open
- Underside vents closed
Each test state allowed the system and drive temperatures to settle before benchmarking was carried out.
Temperatures of the PM951 were recorded under each condition at idle drive state and also the maximum drive temp recorded during the CrystalDiskMark benchmarking test. The sequential read speed was recorded from each test to determine how much (if any) the drive throttled.
RESULTS
OBSERVATIONS
IDLE SYSTEM STATE
Straight away you can see that the PM951 exceeds its claimed sequential read speed by around 50% under normal conditions reaching a massive 1,576MB/s. Great stuff!
During the testing it was observed that throttling occurs in 2 steps, the first step is when the drive hits 70C, the PM951 throttles down to 315MB/s, around one third of its claimed 1000MB/s rating. The second step occurs at 75C where the drive takes a massive dip down to just 71MB/s. it may drop further above 80C but the drive never exceeded this temp.
Focusing on the M.2 Idle temps, you can see that without any active case cooling (0 rpm case fan) the M.2 Drive sits at around 60C when the system is completely idle. This is a worrying temperature sitting just 10C below its throttle temp without any effort.
Activating the system fan to 50% speed reduces the M.2 idle temp down by around 10C, taking the fan up to 100% brings it down a further 10C sitting at a more comfortable 38C.
Running the CrystalDiskmark test caused the PM951 to reach 72C and throttle to 315MB/s without any active cooling, it took less than a minute to pass 70C. With the case fan set to 100% the PM951 reached 59C maximum and maintained its full performance.
Now for the interesting part, covering the vents had the opposite effect to what I was expecting, the PM951 drive temperatures actually reduced in both idle and benchmarking conditions in the region of 5C - 10C. I will talk more about this later.
FULL SYSTEM STRESS STATE
Whilst the system is being put under heavy load and without any active case cooling the system temperature reaches a toasty 57C, the noctua NH-L9i is also nearly flat out trying to keep the CPU under control. Under these conditions the PM951 drive sits at a disturbing idle temperature of 67C, just 3C lower than its throttle point. As soon as the CrystalDisk benchmark is started the drive hits 70C and throttles, and within a minute the drive hits its 75C limit resulting in a read speed of just 71MB/s and maxing out at 80C by the end of the test.
A system case fan speed set to 50% (753 rpm) brings the drive temperature down by 10C during disk benchmarking, but it still experiences some throttling achieving a read speed of 607MB/s.
Taking the fan speed up to 100% (1072 rpm) reduces the idle drive temp by around 10C but doesn't bring the benchmark temperature down below 70C, however it does allow the drive to achieve almost full performance during the disk benchmarking at 1515MB/s.
Again, covering the underside vents up has a positive effect on M.2 drive temperatures, this is completely unexpected and will be discussed in the next section.
UNDER SIDE VENTS
The bottom panel of the LZ7 has a series of vents under the motherboard, the intention of these vents is to allow hot positive pressure air to escape out and apply a cooling effect to M.2 drives mounted on the underside of a motherboard.
However, from the testing carried out so far, it has been observed that covering up vents actually results in lower M.2 drive temperatures in almost all conditions. This is the complete opposite of what was expected.
I have put some serious thought into why this could be, and I think there are 2 possible reasons both of which may be contributing:
REASON 1
On the Gigabyte B150N board, the M.2 Drive is located along the edge near to the GPU which is the opposite side of the board to the case fan. The underside vents sit in between the fan and the drive, it is very possible that the fresh cool air from the case fan is escaping through the vents before it reaches the drive.
Covering the vents forces the cool air from the fan to instead travel all the way along the underside of the motherboard so it reaches the M.2 Drive, the air cools the drive and the heat is then carried toward the GPU side and exits the case.
A possible improvement to the design would be to remove the 'square' vent arrangement (middle of the picture above), and instead increase the width of the GPU underside vents (seen on the left of the picture above).
This theory explains the large difference in temperatures when the fan is running for open and closed vents.
REASON 2
The GPU vents directly out the bottom of the case, it is possible that some of this heat will make its way under the case and travel towards the middle vents, this hot air may be seeping upwards back into the case through the vents and contributing to the M.2 drive temperature. Covering the vents may be preventing this re-circulation from happening.
This theory explains why there is a small difference in temps when the case fan is switched off between open and closed vents.
CONCLUSION
Hopefully your still with me, sorry for the long post!
Without any active case cooling the M.2 PCIe PM951 SSD idles at around 60C with a system temp in the high 40's, this temperature rises to around 67C when the system is put under heavy load. With a throttle temp of 70C it doesn't take much storage activity before throttling occurs with read speeds dropping from 1576MB/s to 315MB/s in a low loaded system and as low as 71MB/s in a heavy loaded system.
Add in some active case cooling and the M.2 drive temperatures reduce to a more acceptable level and are able to sustain their full performance for much longer periods.
Under normal system usage with some level of active case cooling I don't expect that an M.2 PCIe drive will throttle unless you are transferring some really large files one after another.
However, a couple of hours of gaming with higher system temps the PM951 PCIe SSD does begin to struggle, even with good case cooling and ventilation the drive can hit its throttle temp very quickly during sequential reading.
Part of the reason for these high temperatures are that the drives are tucked away under the motherboard and shielded from most of the direct the case cooling. Directing airflow under the motherboard is intended to help with this.
Testing has shown that airflow under the motherboard is key to maintaining full drive performance and vent position play a part in directing the airflow, therefore a small design change will be made to the underside ventilation layout to improve M.2 Drive thermal performance.
*EDIT:
I forgot to mention that this testing was done in 25C ambient thanks to a brief encounter with something called a 'summer' in the UK.
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