When we published our first SSD report in September 2008, an Intel X25-M 80 GB cost around €500. Since then prices have certainly come down and Intel now markets its Intel SSD 320 Series 300 GB at the same price!
An entry level 128 GB SSD such as those tested in our latest article (SSD 2011 roundup: Crucial M4, OCZ Vertex 3, Intel 510/320) remains quite costly however, at €200. The only solution if you’re on a tight budget is to cut down on capacity, with a 64 GB model for example.
The problem is that only Crucial are currently marketing SATA 6G SSDs at this capacity, with the Vertex 3s and Intel SSD 510s only coming in at 120 GB. Is the Crucial solution a good one? We managed to get hold of an M4 64 GB so as to compare it to its predecessor and bring you up to date on the M4 range, versions 64, 128 and 256 GB.
The M4 range
Micron announced the RealSSD C400 at CES in January. A development of the RealSSD C300, this SSD is known as the M4, Crucial being Micron’s consumer arm. Launched one year earlier, the C300 stood out from other SSDs due to its adoption of the SATA 6 Gbits standard which opens the door to theoretical speeds of 600 MB/s, as against 300 MB/s for SATA 3 Gbits. Combined with aggressive pricing and high end random access performance, this was one of the flagship SSDs of 2010.
The M4 is also based on a Marvell 88SS9174 controller but in a more recent revision than the BJP2 used on the C300. In practice we compared a 256 GB version in the BLD2 revision with another at BKK2 (like the 64 and 128 GB models) and performance was identical. According to Crucial, it’s the firmware rather than the chip revision that makes the difference. The Marvell controller comes with a 256 MB DRAM cache, compared to 128 MB on the C300, and the memory used is now 25nm IMFT, while it was 34nm IMFT before.
Here are the performance figures announced by Crucial:
Read speeds are up 16.9% at equal capacity. Write speeds are up by between 26.7 and 20.9%. Although random writes are also up (+11.1 to 33%), the same can’t be said for random reads: 60,000 IOPs on the C300 but just 40,000 IOPS on the M4.
The Crucial M4 64 GB tested combines a Marvell 88SS9174-BKK2 controller, a Micron DRAM chip for the cache and 8 Micron 29F64G08CFACB flash chips. These chips are engraved at 25nm and combine two 32 Gb dies. The size of the pages and blocks is 4 KB and 1 MB respectively. It’s a surprise to find the BKK2 revision used here as the 128 and 256 GB versions use the apparently more recent BL02 revision. Nevertheless, according to Crucial, the firmware is what makes the difference between the C300 and the M4 and not the controller revision.
On the Crucial M4 128 GB, the DRAM chip from Micron is placed on the back and there are now 16 flash chips, though with the same reference.
Unlike the 64 and 128 GB versions, the Crucial M4 256 GB uses 29F128G08CFAAB flash chips. Their capacity is doubled as they use two 64 Gb dies. This time the pages are 8 Kb and the blocks 2 MB.
On the Crucial M4s, 6.9% of the flash memory is used for wear leveling and internal optimisations, which corresponds to the difference between the size of the flash chips (given on a basis of 1 KB = 1024 bytes) and SSD capacity (given on a basis of 1 KB = 1000 bytes).