Micron has finally introduced a second consumer SSD with 3D NAND flash. Rather than a high-performance NVMe drive, they've brought back the entry-level BX product line for the Crucial BX300.

At Computex 2014, Micron introduced the Crucial MX100, the first SSD to use their 16nm MLC NAND. The MX100 was a hit with great performance and great pricing. It was followed up in 2015 by the Crucial MX200, which wasn't much of an improvement over the MX100. But at the same time, Crucial introduced a second product line with the BX100. Using the same 16nm MLC but a cheaper Silicon Motion controller, the Crucial BX100 continued to offer good performance for most purposes and was also the most power efficient SSD of its time.

Later in 2015, the consumer SSD market began to rapidly switch over to TLC NAND: consumers wanted cheaper SSDs, but only Samsung had usable 3D NAND, so planar TLC was the way to increase capacity. Micron introduced the Crucial BX200 in November 2015 as their first SSD to use TLC NAND. The BX200 successfully reduced price per GB, but sacrificed a great deal of performance and power efficiency in the process. The BX200's fate was sealed by drives like the ADATA SP550 that used faster and cheaper SK Hynix TLC to undercut the BX200's pricing while offering somewhat better performance.

Finally, in June 2016 Micron's 3D NAND was ready for mass market use, and the consumer SSD market's race to the bottom was put on hold. Micron introduced the Crucial MX300 using a high-performance Marvell controller like previous MX series SSDs, but using the TLC variant of their 3D NAND rather than MLC. The MX300 thus was serving as successor to both the MX200 and BX200, and it has done the job well with good performance and far better power efficiency than any previous TLC SSD (even considering Samsung's 3D TLC-based 850 EVO).

Crucial MX Series Specifications
Model	MX100	MX200	MX300
Controller	Marvell 88SS9189		Marvell 88SS1074
NAND	Micron 16nm 128Gbit MLC		Micron 384Gbit 32-layer 3D TLC
Capacities	128GB-512GB	250GB-1TB	275GB-2TB
SLC Caching	No	Some Models	Yes
Encryption	TCG Opal 2.0 & IEEE-1667 (eDrive)
Warranty	Three years
Write Endurance	72 TB	80-320 TB	80-400 TB
Launch Date	June 2014	January 2015	June 2016

The main limitation of the Crucial MX300 stems from the odd capacity of Micron's 32-layer 3D TLC parts. The 32L TLC die is Micron's 32L 256Gb MLC operated as a TLC chip, yielding a capacity of 384Gb (48GB) per die. It is awkward to build SSDs with standard power of two capacities out of such chips, so Micron initially introduced the MX300 with a 750GB (768GB raw) capacity model. The rest of the MX300 lineup used capacities that were slightly above the standard sizes (eg. 525GB instead of 512GB), which still left the MX300 with more overprovisioning than a typical consumer SSD. The odd capacity effect is most pronounced with the smallest MX300, the 275GB model. Micron didn't go any smaller than that because a drive in the ballpark of 128GB would use only three TLC dies, wasting one of the four channels on most SATA SSD controllers.

Micron's upcoming second generation 3D NAND parts are designed with TLC in mind as the primary use, and Micron will be producing both 256Gb and 512Gb parts. But this new 64-layer 3D NAND is still ramping up in production. Intel has shipped limited quantities in their 545s, but most of the early 64L NAND is going to the enterprise SSD market.

That's where the new Crucial BX300 comes in. The BX300 brings MLC NAND back to the Crucial product line for the sake of making smaller capacity entry-level SSDs. The Crucial BX300 will be produced in capacities from 120GB to 480GB using Micron's 256Gb 32L 3D MLC. Micron is again using a Silicon Motion controller for the BX line, this time the SM2258. Micron has not opted to use the DRAMless SM2258XT variant and instead has equipped the BX200 with 256MB to 512MB of their own DDR3.

Crucial BX Series Specifications
Model	BX100	BX200	BX300
Controller	Silicon Motion SM2246EN	Silicon Motion SM2256	Silicon Motion SM2258
NAND	Micron 16nm 128Gbit MLC	Micron 16nm 128Gbit TLC	Micron 256Gbit 32-layer 3D MLC
Capacities	120GB-1TB	240GB-960GB	120GB-480GB
SLC Caching	No	Yes	Yes
Encryption	None
Warranty	Three years
Write Endurance	72 TB	72 TB	55-160 TB
Launch Date	January 2015	November 2015	August 2017

On paper, the BX300 does not appear to be making any significant compromises to reach low price points. In some respects it is superior to the MX300, and it certainly seems like it will have lower profit margins for Micron. The BX300 may be the kind of product that only a vertically-integrated manufacturer like Micron can successfully bring to market in the midst of an industry-wide NAND shortage. ADATA uses the same controller and NAND in their SU900 and SX950 SSDs, but those are selling for significantly higher prices than the Crucial MX300, not lower. The BX300 may turn out to be a short-lived stopgap product to go after a segment of the market that the MX300 is ill-suited for. A replacement for both the MX300 and BX300 using 64L TLC will probably show up as soon as Micron can spare the NAND. Certainly by Computex in June 2018 we should expect a new product, but I wouldn't be surprised to hear about something at CES in January.

Crucial BX300 Specifications
Capacity	120GB	240GB	480GB
Form Factors	2.5" 7mm
Controller	Silicon Motion SM2258
NAND	Micron 256Gbit 32-layer 3D MLC
DRAM (DDR3)	256MB	256MB	512MB
SLC Write Cache	4GB	8GB	16GB
Sequential Read	555 MB/s	555 MB/s	555 MB/s
Sequential Write	510 MB/s	510 MB/s	510 MB/s
4KB Random Read	45k IOPS	84k IOPS	95k IOPS
4KB Random Write	90k IOPS	90k IOPS	90k IOPS
Encryption	No
Write Endurance	55 TB	80 TB	160 TB
Warranty	Three years
MSRP	$59.99	$89.99	$149.99

The Crucial BX300 is Micron's first MLC-based consumer SSD since the Crucial MX200. With the MX200, Micron experimented with using SLC caching on smaller capacities and had mixed success—peak performance was boosted a bit, but at the cost of creating more background work for the controller that hurt sustained workloads. For the Crucial BX300, Micron is using relatively small fixed-size SLC caches. Sequential performance and random write performance are rated the same across all three capacities, while random read performance is reduced a bit for the 240GB and is cut in half for the 120GB model. The rated write endurance numbers are probably chosen simply to be lower than the ostensibly higher-end MX300 model, rather than being based on actually lower expectations for drive lifetime. The MX300 does have lots of overprovisioning with which to reduce write amplification, but the BX300 has a reasonable amount too and the advantage of inherently higher endurance from using MLC instead of TLC.

For this review, the our 480GB Crucial BX300 will primarily be compared against:

• The Crucial MX300 525GB: Micron's other consumer SSD, based on 3D TLC NAND
• The Crucial BX200 480GB: Micron's first TLC SSD and the nominal predecessor to the BX300.
• The Crucial MX200 500GB: The last MLC-based consumer SSD from Micron.
• The Intel SSD 545s 512GB: Based on newer 64L 3D TLC NAND and the newer Silicon Motion SM2259 controller
• The ADATA Utimate SU800 512GB: Using the same SM2258 controller as the BX300 but Micron's 3D TLC like the MX300.
• Samsung 850 PRO 512GB and 850 EVO 500GB: Samsung's SATA SSDs with 3D MLC and 3D TLC respectively

AnandTech 2017 SSD Testbed
CPU	Intel Xeon E3 1240 v5
Motherboard	ASRock Fatal1ty E3V5 Performance Gaming/OC
Chipset	Intel C232
Memory	4x 8GB G.SKILL Ripjaws DDR4-2400 CL15
Graphics	AMD Radeon HD 5450, 1920x1200@60Hz
Software	Windows 10 x64, version 1703
	Linux kernel version 4.12, fio version 2.21

• Thanks to Intel for the Xeon E3 1240 v5 CPU
• Thanks to ASRock for the E3V5 Performance Gaming/OC
• Thanks to G.SKILL for the Ripjaws DDR4-2400 RAM
• Thanks to Corsair for the RM750 power supply, Carbide 200R case, and Hydro H60 CPU cooler

AnandTech Storage Bench - The Destroyer

The Destroyer is an extremely long test replicating the access patterns of very IO-intensive desktop usage. A detailed breakdown can be found in this article. Like real-world usage, the drives do get the occasional break that allows for some background garbage collection and flushing caches, but those idle times are limited to 25ms so that it doesn't take all week to run the test. These AnandTech Storage Bench (ATSB) tests do not involve running the actual applications that generated the workloads, so the scores are relatively insensitive to changes in CPU performance and RAM from our new testbed, but the jump to a newer version of Windows and the newer storage drivers can have an impact.

We quantify performance on this test by reporting the drive's average data throughput, the average latency of the I/O operations, and the total energy used by the drive over the course of the test.

The Crucial BX300 is tied for second-fastest average data rate on The Destroyer among SATA drives. The BX300's performance falls between the Samsung 850 EVO and 850 PRO, and matches the Intel 545s that uses a newer generation of 3D NAND and a newer SSD controller.

The BX300's latency during The Destroyer is best in class, with both average and 99th percentile latencies at the top of the chart.

Breaking the average latency score down by read and write operations, we find the BX300 in second place for each subscore, but with a different drive in first place each time: the 850 PRO is what beats the BX300's average read latency, and the Crucial MX200 beats the BX300's average write latency.

The Crucial BX300 does a great job keeping read latency low throughout the destroyer, with the lowest 99th percentile read latency out of this bunch of drives. By contrast, the 99th percentile write latency only ranks third, behind the Intel 545s and Samsung 850 PRO. The MX300's 99th percentile write latency is moderately worse than the BX300's, but its 99th percentile read latency is almost twice as high.

The BX300 further improves on the power efficiency of the MX300, but not enough to match the Intel 545s that benefits both from a newer Silicon Motion controller and from newer 64L 3D NAND.

AnandTech Storage Bench - Heavy

Our Heavy storage benchmark is proportionally more write-heavy than The Destroyer, but much shorter overall. The total writes in the Heavy test aren't enough to fill the drive, so performance never drops down to steady state. This test is far more representative of a power user's day to day usage, and is heavily influenced by the drive's peak performance. The Heavy workload test details can be found here. This test is run twice, once on a freshly erased drive and once after filling the drive with sequential writes.

When the Heavy test is run on an empty drive, the Crucial BX300's average data rate is not quite as fast as the drives using Micron's 3D TLC with large SLC caches. The situation is very different when the test is run on a full drive: the ADATA SU800 and Crucial MX300 are far slower, while the Crucial BX300 retains almost all of its performance and ends up placing right behind the Samsung 850 PRO and EVO.

The average latency and 99th percentile latency of the BX300 on the Heavy test are slower than most of the other drives in this bunch except the BX200. It is again very clear that the Micron 3D TLC drives have serious problems when the drive is full, but the BX300 handles that situation fine.

The average read latency of the BX300 is faster than the Crucial MX drives and the Intel 545s, while the BX300's average write latency is slower than those, though not to a worrying degree. Samsung comes out ahead for both reads and writes, though the ADATA SU800 is competitive provided the test isn't run on a full drive.

The 99th percentile read latency of the Crucial BX300 is a bit slower than the Samsung 850 PRO but clearly faster than any other Crucial drive and is also ahead of the Samsung 850 EVO. The 99th percentile write latency of the BX300 is about twice as high as most of its competition, though when full the MX300 and ADATA SU800 show even higher latency.

The Crucial BX300 is tied for second place with the Samsung 850 EVO for power efficiency on the Heavy test. The MX300 uses substantially less power when the test is run on an empty drive, but significantly more power when the test is run on a full drive.

AnandTech Storage Bench - Light

Our Light storage test has relatively more sequential accesses and lower queue depths than The Destroyer or the Heavy test, and it's by far the shortest test overall. It's based largely on applications that aren't highly dependent on storage performance, so this is a test more of application launch times and file load times. This test can be seen as the sum of all the little delays in daily usage, but with the idle times trimmed to 25ms it takes less than half an hour to run. Details of the Light test can be found here. As with the ATSB Heavy test, this test is run with the drive both freshly erased and empty, and after filling the drive with sequential writes.

The Crucial SSDs occupy the bottom half of the average data rate rankings for the Light test, as the other 3D NAND SSDs in this bunch are able to deliver higher peak performance. The BX300 is slower than the MX300 when the test is run on an empty drive, but for a full drive the BX300 is the fastest Crucial SSD and also faster than the ADATA SU800.

The average and 99th percentile latency scores for the BX300 are worse than the other 3D NAND SSDs in this comparison, but there's enough of a gap for it to matter.

The average read latency of the Crucial BX300 on the Light test is better than any other Crucial drive, but is unimpressive compared to the 3D NAND SSDs from other brands. The average write latency is significantly higher than most of the other SSDs (excepting the BX200), but is not enough to cause real problems for light workloads.

The 99th percentile read and write latencies tell pretty much the same story as the averages for the BX300: it performs fine for read operations, but is a bit slower for writes.

The Crucial BX300 turns in another second-place score for power efficiency, behind the MX300. The Light test doesn't put too much stress on the MX300's SLC caching, so it keeps its first-place efficiency even when the test is run on a full drive.

Random Read Performance

Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Each burst consists of a total of 32MB of 4kB random reads, from a 16GB span of the disk. The total data read is 1GB.

The burst random read performance of the Crucial BX300 is better than the previous Crucial SSDs, but still trails behind quite a few other MLC SSDs and the two fastest 3D TLC SSDs.

 

Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.

On a longer test of random read performance and with some higher queue depths in play, the Crucial BX300 ends up falling behind the MX200 but is substantially faster than the MX300 and most other TLC SSDs. Most of the MLC SSDs and the 3D TLC-based Samsung 850 EVO and Intel 545s significantly outperform the Crucial BX300.

The power efficiency of the Crucial BX300 when performing random reads is a bit below average for SATA SSDs, with a few planar TLC SSDs beating it.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

With a high enough queue depth, the Crucial BX300 delivers random read performance that is as good as any SATA drive of this capacity, but it also requires quite a bit of power to perform that well. At more modest queue depths, the BX300 underperforms most of its competition-especially the Samsung drives, which saturate at QD16.

Random Write Performance

Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.

The Crucial BX300's QD1 burst random write performance is tied with the Samsung 850 EVO for second place, slightly behind the ADATA SP550 of all things. Crucial's MX300 is only about 6% slower, while the Samsung 850 PRO is about 16% slower.

 

As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.

With a longer test duration and higher queue depths, the Crucial BX300 holds on to second place, this time scoring just behind the Crucial MX200. The Samsung 850s are just a hair slower than the BX300, and the Crucial MX300 is the next fastest.

In terms of power efficiency during the random write test, the BX300 is again in second place, with the MX300 holding on to a safe lead. The BX200's efficiency was abysmal, and the BX300 provides four times the performance per Watt on this test.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

The Crucial BX300 scales to near saturation by QD4, but power consumption keeps increasing up to QD8. The performance curve for the MX300 is just below the BX300's, but the power consumption of the MX300 stays significantly lower and even the slowest drives end up drawing more power than the MX300.

Sequential Read Performance

Our first test of sequential read performance uses short bursts of 128MB, issued as 128kB operations with no queuing. The test averages performance across eight bursts for a total of 1GB of data transferred from a drive containing 16GB of data. Between each burst the drive is given enough idle time to keep the overall duty cycle at 20%.

The sequential read burst speed of the Crucial BX300 is faster than any previous Crucial drive, but only just barely catches up to the rest of the market.

 

Our test of sustained sequential reads uses queue depths from 1 to 32, with the performance and power scores computed as the average of QD1, QD2 and QD4. Each queue depth is tested for up to one minute or 32GB transferred, from a drive containing 64GB of data.

The sustained sequential read performance of the BX300 actually shows a regression from the BX200, though both drives fall in the middle of the pack and above Crucial's MX drives. The fastest SATA SSD (Samsung 850 PRO) is 45% faster than the BX300, and even the Intel 545s is 22% faster.

The power efficiency of the Crucial BX300 on the sequential read test is poor, and the other two drives that use Micron's 3D NAND (as TLC) join the BX300 at the bottom of the chart. The Intel 545s does well on this efficiency score, so Micron will probably be able to shore up this weakness in future products when they adopt their 64L 3D NAND.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

Samsung's SSDs are the best-behaved on this test, with performance saturating at QD2 and consistently staying there through the rest of the test. The MX300 is also quite consistent through this test, but with much lower performance overall.

Sequential Write Performance

Our test of sequential write burst performance is structured identically to the sequential read burst performance test save for the direction of the data transfer. Each burst writes 128MB as 128kB operations issued at QD1, for a total of 1GB of data written to a drive containing 16GB of data.

The burst sequential write speed of the BX300 is good, but not enough for it to stand out from the crowd or to beat the MX200. The MX300 stands out for being substantially slower than most SATA SSDs.

 

Our test of sustained sequential writes is structured identically to our sustained sequential read test, save for the direction of the data transfers. Queue depths range from 1 to 32 and each queue depth is tested for up to one minute or 32GB, followed by up to one minute of idle time for the drive to cool off and perform garbage collection. The test is confined to a 64GB span of the drive.

On the longer sequential write test, the BX300 stays in the top half of the chart and performs close to the top tier of drives, but is a bit slow given that it uses 3D MLC.

The power efficiency of the Crucial BX300 is a bit better than Samsung's SSDs, but the drives using Micron's 3D TLC are more efficient and Toshiba's OCZ VX500 is in the lead by a substantial margin.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

The Crucial BX300's sequential write speed saturates at QD4 and it performs steadily thereafter, but at QD2 it is much slower than its maximum and is outperformed by many SSDs.

Mixed Random Performance

Our test of mixed random reads and writes covers mixes varying from pure reads to pure writes at 10% increments. Each mix is tested for up to 1 minute or 32GB of data transferred. The test is conducted with a queue depth of 4, and is limited to a 64GB span of the drive. In between each mix, the drive is given idle time of up to one minute so that the overall duty cycle is 50%.

The mixed random I/O performance if the Crucial BX300 puts it in the second tier of SATA SSDs, with Samsung's 850s forming the top tier. The Crucial MX300 is a bit slower than the BX300.

With the exception of the Crucial MX200, all of the drives that outperformed the BX300 are also more efficient. The MX300 is also significantly more efficient despite being slightly slower.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

The Crucial BX300's performance on the mixed random I/O test increases slowly as the proportion of writes grows, and it accelerates near the end of the test. The power consumption is flat across almost all of the test, but ticks up as the workload shifts to pure writes.

Samsung's drives are faster than the BX300 across the entire test, while the Intel 545s and Crucial MX200 managed higher average performance scores by performing better on the read-heavy portions of the test and a bit worse during the write-heavy phases.

Mixed Sequential Performance

Our test of mixed sequential reads and writes differs from the mixed random I/O test by performing 128kB sequential accesses rather than 4kB accesses at random locations, and the sequential test is conducted at queue depth 1. The range of mixes tested is the same, and the timing and limits on data transfers are also the same as above.

The Crucial BX300 performs very well on the mixed sequential I/O test, slightly ahead of the Samsung 850 EVO and only 5% slower than the 850 PRO. The MX300 scores closer to the middle of the pack, while the BX200 and MX200 are near the bottom.

The Crucial BX300's power efficiency score isn't quite as close to the top score, but only because Toshiba's OCZ VX500 really stands out from the crowd. The BX300 is ahead of the Samsung 850 PRO and close to the 850 EVO, MX300, and Intel 545s.

Crucial BX300 480GBIntel SSD 545s 512GBSamsung 850 EVO 500GBSamsung 850 PRO 512GBCrucial BX200 480GBPNY CS1311 480GBPNY CS2211 480GBSanDisk Extreme Pro 480GBCrucial MX200 500GBCrucial MX300 525GBPlextor S2C 512GBADATA Premier SP550 480GBADATA Ultimate SU800 512GBOCZ Trion 150 480GBOCZ VX500 512GB

The BX300's performance doesn't change much over the course of the mixed sequental test, but it does speed up a bit near the end. Power consumption starts out high but drops dramatically across the first half of the test, and then follows the shape of the performance curve.

Power Management

Real-world client storage workloads leave SSDs idle most of the time, so the active power measurements presented earlier in this review only account for a small part of what determines a drive's suitability for battery-powered use. Especially under light use, the power efficiency of a SSD is determined mostly be how well it can save power when idle.

SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.

Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.

We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled.

The active idle power consumption of the Crucial BX300 is the same as for the BX200. Both are a bit on the high side, but there are Silicon Motion drives with both higher and lower active idle draws. With SATA link power management enabled, the BX300's idle power draw is better than average, but 20mW worse than what the BX200 and Intel 545s manage with older and newer Silicon Motion controllers.

The BX200 had a serious problem with idle wake-up latency of over 10ms, which the BX300 has fixed. The BX300 wakes up quickly, though the drives with the Phison S10 controller are still the quickest by far.

Final Words

The Crucial BX200 comes in last place as often as not. The Crucial BX300 doesn't entirely reverse that, but it still provides one of the biggest generational jumps the SSD market has seen. Micron has learned from their mistakes with the BX200 and produced a worthy successor to the BX100. With the MX300 doing so well as a mainstream SSD with entry-level pricing, the focus of the BX line has shifted from simply being the cheaper option to being the drive designed specifically for the smaller capacities demanded by cost-conscious consumers.

Micron's large 384Gb 3D TLC die is ill-suited to making small SSDs, as 120-128GB SSDs end up only having 3 NAND chips on a four-channel controller, and even at larger capacities the flash is not well balanced across the controller channels. For the next generation of 3D NAND, Micron is addressing this issue by manufacturing both a large 512Gb die and a smaller 256Gb die. Since that 64-layer 3D NAND is still ramping up to full production, Micron has chosen for the BX300 to use their 256Gb 3D MLC that allows for a small SSD to be reasonably fast and free of the downsides of the TLC NAND that dominates the entry-level SSD market.

It's a bit of a puzzle how Micron can afford to sell an MLC SSD for less than their TLC SSD without making serious compromises elsewhere like using a DRAMless controller. But as long as they're willing to sell the BX300 at these prices, it's a great product.

The BX300 only has a few notable weaknesses. Micron's 32L 3D NAND is unusually power-hungry during sequential reads, despite being otherwise quite efficient. This also affects random reads to some extent. The BX300's peak performance is on average slightly below top-tier SATA drives like Samsung's 850 PRO and EVO and the Intel 545s, and it is outperformed by other 3D TLC drives like the MX300 and ADATA SU800 when they're able to make good use of their SLC caches. But this is offset by how well the BX300 retains its performance under heavier workloads and when operating with a nearly-full drive. In that respect, it has a significant advantage over the Crucial MX300.

	120-128GB	240-275GB	480-525GB	960-1050GB	2TB
Crucial BX300	$59.99 (50¢/GB)	$89.99 (38¢/GB)	$149.99 (31¢/GB)
Crucial MX300		$99.99 (40¢/GB)	$159.99 (32¢/GB)	$289.99 (29¢/GB)	$549.00 (27¢/GB)
ADATA SU800	$56.68 (44¢/GB)	$91.99 (36¢/GB)	$168.58 (33¢/GB)	$265.00 (26¢/GB)
ADATA SU900		$108.99 (43¢/GB)	$197.80 (39¢/GB)
ADATA XPG SX950		$109.99 (46¢/GB)	$214.99 (45¢/GB)
Intel SSD 545s		$99.99 (39¢/GB)	$169.99 (33¢/GB)
Samsung 850 PRO		$114.99 (45¢/GB)	$212.19 (41¢/GB)	$420.99 (41¢/GB)	$897.99 (44¢/GB)
Samsung 850 EVO		$89.99 (36¢/GB)	$174.75 (35¢/GB)	$299.99 (30¢/GB)	$715.00 (36¢/GB)

The Samsung 850 EVO is available with very competitive pricing at the moment, shutting many drives using Micron 32L 3D NAND out of the market. The MSRP of the 480GB BX300 we tested is low enough to beat basically everything on a price per GB basis, and is far enough below the Samsung 850 EVO that it isn't an automatic decision to get the Samsung instead. The 240GB BX300 will debut with the same price as the 250GB Samsung 850 EVO, making the Samsung the better option for now.

The smallest capacity of the Crucial BX300 may prove to be the most popular and most competitive. There are other 120GB drives on the market that are priced a bit lower, but the BX300 has the advantage that it uses 3D MLC NAND, doesn't use a DRAMless controller and uses all four NAND channels on its controller. The 120GB BX300 will be slower than the 480GB model we tested, but it will retain the general characteristic of performing almost as well when it is full as when empty. This is far more important at such small capacities. The 120GB BX300 also benefits from lack of competition from Samsung: the planar TLC-based 750 EVO is not available at competitive prices and the 120GB 850 EVO and 128GB 850 PRO were discontinued when Samsung moved from 32L 3D NAND to 48L 3D NAND.