Crucial BX300 480GB SSD Review

by AkG     |     August 29, 2017

BX vs. MX: New Similarities & Differences

Due to the rather unique nature of the BX300 it is almost assured that potential buyers are going to draw comparisons between it and the MX300 it replaces, or eclipses or resides alongside in Crucial's line up. As such we are going to go over these differences so that you can make an informed decision on which option is best for you. These differences and similarities do run the gamut from minor to major but coalesce into a virtual reversal of fortune for the plucky underdog BX series.

The most obvious change in just one generation is the asking price of the BX series. Crucial has always prided themselves on having some of best price per Gigabyte models available on the market. In the past it was the BX leading the way on how little buyers had to spend, and the MX following closely behind offering slightly higher prices but noticeably better performance. This one-two combination is why we have referred to them as the juggernaut of the industry. Few could match this pair and fewer still could beat its value.

This time around the BX300 is actually more expensive than a similar capacity MX300. The MX300 series costs about 25 to 30 cents (USD) per Gigabyte and while some pundits were wondering how low the BX series would go the opposite is true. The new BX series ranges from a whopping fifty cents per gigabyte (BX300 120GB) to a more reasonable but still slightly - higher thirty one cents per gigabyte (BX300 480GB). What this means to buyers is that the BX300 really is not going to offer much if any savings compared to a comparatively sized MX300. Talk about bucking industry trends.

This situation is certainly a first for the BX line but not all that unexpected as Crucial has also flipped the status quo on the NAND being used. BX models were always the lower priced models which relied upon more value oriented NAND, while the MX series may have cost a few cents per Gigabyte more but made up for it with superior NAND and thus performance. This time the BX300 is actually on the bleeding edge of technology as it is the first Crucial SSD to make use of their long promised MLC 3D CuA NAND. As such the new BX actually uses superior NAND compared to the MX series. That too is a first for the Crucial BX series which was previously never used as a showcase model.

This new NAND is how Crucial is easily able to justify the asking price of the BX300 series. In addition, this new BX model may indeed use a pseudo-SLC 'Dynamic Write Acceleration' buffer (4GB to 16GB depending on the capacity) but, unlike the MX300 series whose performance dips noticeably when this buffer is exhausted, this MLC NAND based drive's performance will not go in the toilet when it has to write directly to the NAND. This is because TLC has to be written to slower than MLC so as to ensure this relatively fragile NAND is not harmed by a simple write. As we will show later in the review this does translate to dramatically increased real world performance.

The NAND being used here is not only capable of higher throughput but also happens to be more durable as MLC is just more robust than TLC. Then to confuse consumers even more on why Crucial decided call this new creation a 'BX' instead of a 'MX', or even add another brand to their lineup, the BX300 models come equipped with more over-provisioning than similarly sized MX300 models.

There is no comparison to be made with the BX300 120GB's 8GB of over-provisioning as the MX300 simply does not go down that low. However even excluding the 120GB model from the equation the BX300 240GB comes with 16GB of over-provisioning. This is more than all but the EOL'ed MX300 750GB that had 18GB set aside. Meanwhile the 32GB of over-provisioning the BX300 480GB comes with is more than any sized MX300 including the cavernous 2TB MX300 model. This level of over-provisioning means that not only is the NAND more durable but there is more of it in reserve to replace dead cells, and help boost performance when the drive is in a 'dirty' state.

This increase over-provisioning is all due to the NAND technology Crucial opted for. As already pointed out the BX300 makes use of MLC 3D CuA NAND instead of TLC 3D CuA NAND. The TLC version has 48GB per layer NAND and a big reason why the MX300 has such oddball capacities. The MLC version is 'only' 32GB per layer and as such industry standard capacities allow for more streamlined levels of over-provisioning. This is why the MX300 is 120GB (128GB real capacity), 240GB (248GB real capacity), and 480GB (512GB real capacity).

The side-effect of using different NAND also translates into noticeably better performance at similar capacity points. This is because both the MX and BX 300 generation have quad channel controllers and it simply takes more NAND layers to hit a given capacity using 2bit MLC instead of 3bits per cell TLC. For example, the MX300 275GB (really a 288GB drive) only has six layers of NAND to spread across the four channels. This results is all four channels have only a single layer of NAND on each channel with two of the four channels having a second layer (i.e. 1/2/1/2 configuration). The BX300 240GB on the other hand has two layers on each and every channel. This difference only gets larger as the BX300 scales up. Right now Crucial is artificially limiting capacities to 480GB, whereas the BX200 topped out at 960GB, but even here the difference is already noticeable with 4 layers vs less than 3 layers (MX300 525GB with a 2/3/3/3 configuration) on each channel.

In order to keep the BX300 from entirely eating the MX300's smaller capacity versions' market share Crucial is using a lower power controller for the BX300 series. The SM2258 certainly is powerful enough for the entry level marketplace but it is a somewhat unfortunate design choice by Crucial. Consumers and critics alike will not be able to see the true potential of this NAND until it is paired with either a high performance 8 channel SATA controller, or more optimally a NVMe based one.

Further helping to distinguish the BX300 from the MX300 in the hearts and minds of buyers is the method in which each series protects data in the event of an unexpected loss of power. As we have outlined in previous MX300 reviews, the MX300 series uses a hardware based design to insure data loss protection. Literally the onboard capacitors allow the MX300 controller to mostly - finish what it is doing before doing a controlled shutdown.

The BX300 does things differently. Instead of using onboard capacitors the it just like the BX200 relies upon firmware algorithms for data safety. What this means is the controller is nearly constantly doing backups of master boot record changes so that data corruption is minimized. What it does not do however is cover off any data that has been marked as written by the OS but is in fact still in the RAM cache buffer. This data is a near total write off and can cause data corruption to occur. Its coverage is still adequate for the home user and non-mission critical data, but certainly not in the same class as the MX300s.

As you can see buyers do indeed face a difficult choice. Buyers can either get more durable NAND with better NAND interleaving and better levels of over-provisioning; or they can spend a bit less and get a MX300 that has better data loss protection, a better controller, but less robust and slower NAND. That is indeed a difficult decision, but only one you can make based upon your specific requirements and preferences. 

Latest Reviews in Storage
March 6, 2018
The Crucial MX500 follows in the footsteps of some of the best SSDs; the MX300 and MX200. But in a very competitive market, can it even compete these days?...
February 25, 2018
It is the FASTEST SSD we've ever tested, providing unbelievable benchmark performance but the Intel Optane SSD 900P also has some very serious limitations....
January 9, 2018
Toshiba has announced the new RC100 NVMe M.2 SSD Series, which targets value-oriented gamers, DIY system builders, and system integrators....