If you have wondered what caused SSD prices to drop so dramatically in the last few years, it has more to do than just competition. Higher density NAND is what has led the charge in plummeting prices; with the ability to cram more storage onto a package, the overall price goes down.
This comes with some drawbacks, however. As you know from reading our SSD reviews, controllers need to be able to access as much memory in parallel as possible. How much it takes to fully saturate a controller (and the SATA bus) depends on various factors, but generally the more channels it has to work with, the better, to a certain point.
This can be easily demonstrated by reading our Intel SSD 525 review, where we tested the exact same product in five different capacities ranging from 30GB to 240GB. The Sandforce controller in each drive gets to access either 4, 8, 16, 24, or 32 channels depending on capacity, and it seems to cap out at 24. Anything lower than that, and performance suffers. This has been the case for years – SSD performance generally reached its peak at 180 GB or so. Anything above that won’t be any faster, but anything below will be slower.
If a drive’s capacity is high enough, manufacturers can get away with using higher density NAND, as the parallel channels will be the same. However, what Crucial did with the M500 is was use 16GB NAND packages on capacities like 120GB and 240GB. Sequential write performance on the 120GB topped out at 130 MB/s. Compare that to the 480GB version at 400 MB/s. Because of this, they had trouble competing with competing drives in the most common capacities sold. Peak performance wasn’t achieved until you got to the 480GB model.
The Crucial M550 addresses this directly, by using 8GB packages. They also upgraded the Marvell controller to a newer model (88SS9189, from 9187), and have significantly lowered the amount of overprovisioned NAND, but I think it’s the new (well, old actually) lower-density flash that makes the most difference.
Crucial M550 Review
The Crucial M550 is not a direct replacement to the M500. Instead, it will be sold alongside it as a high performance option. We will be comparing it to other performance SSDs from Intel, OCZ, Samsung, and others.
The Crucial M550 continues their unique design philosophy of placing the labels on the opposite sides of what other manufacturers do. I guess it doesn’t really matter if you’re never going to see it, but there you go.
The Crucial M550 features Micron NAND and RAM of course (in case you weren’t aware, Crucial is simply the retail brand for Micron), and the newest Marvell controller. Seeing a DDR cache is nothing new on an SSD – almost all of them use it in some way. In this case, the capacity is 512MB for all sizes except for the 1TB model. That one gets 1GB of cache.
At the top right you will see a series of capacitors, which are what allows the M550 to have write protection. This is a feature we’re used to seeing on enterprise SSDs, and it’s nice to see it on retail drives like this. It should be considered essential for the Crucial M550 (and all Marvell controlled drives) since they don’t work properly in Windows without write caching enabled. 
On the next page, we’ll take a look at how the Crucial M550 performs, compared to some of the most common drives sold in the last few years.
