The ADATA Premier SP550 SSD Review: A Second Look At Silicon Motion's SM2256 Controller
by Billy Tallis on March 23, 2016 8:30 AM ESTFinal Words
Wrapping things up, I want to return to the broader question of what the ADATA SP550 does for the SM2256's reputation. In short, it helps a lot. The SM2256 clearly isn't the blockbuster that the SM2246EN controller was and isn't fully living up to the original expectations, but it does now have a place in the market.
To that end the ADATA Premier SP550 takes shape as a properly working implementation of an SM2256-based SSD, without the ugly surprises of the Crucial BX200. Write speeds - both sequential and random - are an acute weakness, though this admittedly is nothing new for a low-end TLC drives and at this point is becoming a known trade-off to reach lower prices. Unfortunately this also means that it still lags behind the prototype that used Samsung NAND and that it rarely pulls ahead of the pack of retail competitors. Meanwhile latency is consistently worse than drives based on other controller architectures that have multi-core processors.
The unexpected bright spot is that the SP550 exhibits relatively little performance degradation from a full drive. On the ATSB Light and Heavy tests the SP550's average data rate is lower than that of the OCZ Trion 100 when the test is run on an empty drive, but the SP550 comes out ahead when the drives are full. This effect also shows up when comparing the random write test against the steady-state performance: the SP550 is in last place on the shorter test but ranks much higher on the longer test. This is an important advantage for the 120GB model, which is the easiest to accidentally fill up. Since the 120GB SP550 is also the cheapest 120GB SSD at the moment, it's a reasonable pick for consumers trying to save every dollar possible.
At higher capacities it is much easier to justify spending a few dollars more for improved performance, and it's much easier to keep some free space on the drive. The 960GB model in particular won't make sense unless its price comes down substantially; that capacity was released more recently but probably can't compete against newer Phison drives, let alone the MLC-based Mushkin Reactor 1TB that is only $10 more. In the 480GB range the OCZ Trion 100 is priced very close and performs close albeit with different strengths and weaknesses. But again MLC drives like PNY's CS2211 aren't that much more expensive. Otherwise in the 240GB class there's not much that can compete with the SP550's price, and none of them can clearly beat it on performance.
| Value SSD Price Comparison | ||||
| Drive | 960GB | 480GB | 240GB | 120GB |
| ADATA SP550 | $219.99 | $112.99 | $57.99 | $38.99 |
| PNY CS1311 | $229.99 | $119.99 | $59.99 | $39.99 |
| OCZ Trion 100 | $199.99 | $114.99 | $64.95 | $54.99 |
| OCZ Trion 150 | $255.99 | $133.49 | $72.26 | $52.96 |
| Crucial BX200 | $259.27 | $128.50 | $64.99 | |
| SanDisk Ultra II | $224.65 | $129.99 | $74.99 | $54.99 |
Ultimately the bottom of the SSD market is crowded and it's hard to make a product stand out, especially as the limiting factor in both cost and performance is frequently the NAND. No value drive is without its faults and there's no clear top performer in this segment. But the ADATA SP550 does manage to stand out unambiguously with the best pricing at 120GB and 240GB while not earning notoriety for its performance. We can't reasonably demand more than that from a value drive.
As for the SM2256 controller, it's clear that Silicon Motion is learning to deal with the challenges of managing TLC flash, and many of the remaining weaknesses exhibited by the SP550 can be blamed on the limitations of the flash rather than the controller. For the impending transition to 3D NAND, the SM2246EN controller will be sticking around for MLC drives, but the SM2256 will be updated to SM2258 for 3D TLC. This suggests that Silicon Motion may be addressing more shortcomings in order to be ready to play a bigger role in the budget TLC SSD market with the next generation of drives.
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tipoo - Wednesday, March 23, 2016 - link
I never really thought about core counts in storage controllers before this review. What would your average mid range and high end SSDs have for controller CPUs?I think I also remember looking into this model for a cheap old laptop upgrade, but some reviews mentioned it didn't have a DRAM cache which made performance consistency very not consistent. That looks similar here in the charts, is this the one with no DRAM?
vladx - Wednesday, March 23, 2016 - link
Most SSD controllers use dual or tri-core ARM Cortex-R4 configurations.MrCommunistGen - Wednesday, March 23, 2016 - link
The 2TB 850Pro/EVO article here on Anandtech has a table showing core counts and clock speeds of the recent Samsung SSD controllers: MDX, MEX, MGX, MHX, all of which are 3-core ARM Cortex R4 except for the MGX which is a dual core ARM Cortex R4.The breakdown is a bit complex but it looks like MDX is 840/840 Pro. MEX is 840 EVO, 128-1TB 850 Pro, and 1TB 850 EVO. MGX is 120-500GB 850 EVO, and MHX is in the 2TB 850 Pro/EVO.
Going through historical articles (840 Pro review) I found that the Samsung 830's controller was called the MCX and it is implied but not directly stated that it was a 3-core ARM9 design.
Not to toot my own horn, but the "Update" in the 840 Pro article regarding MDX being R4 rather than ARM9 was at least partially due to an email chain I had with Anand. Yes, I emailed him instead of blasting him in the comments section. As I recall, he said the original press kit had said ARM9. I'd seen Cortex-R4 elsewhere on the 'net, and Anand reached out to Samsung for confirmation. I assume he got it because he updated the article later that day.
I don't remember seeing much info on core counts for other controllers, but the 840 Pro article also has a table where it notes DRAM Size for various controllers of the time. What's notable to me is that the old Intel controllers like in the X25M G2 didn't cache user data, only the mapping tables, so the G3 is listed in the table as using up to 64MB cache.
Also notable is that the SandForce controllers didn't use a DRAM cache - probably a large part of their huge industry success, in addition to their (at the time) class leading performance, and the fact that they sold turn-key solutions to OEMs.
Billy Tallis - Wednesday, March 23, 2016 - link
The SP550 uses Samsung DRAM. Silicon Motion does have a controller designed for DRAM-less MLC drives, but their controllers for TLC SSDs all still have a DRAM controller. I've been told that it's theoretically possible to use SM2256 or SM2258 without external DRAM, but I don't know if anyone has actually written the firmware necessary to accomplish that. The performance hit of operating without external DRAM is so far something that is usually only acceptable for USB drives, not mass-market SATA SSDs.hojnikb - Wednesday, March 23, 2016 - link
Well, sandforce and sm246xt perform just fine without dramghanz - Wednesday, March 23, 2016 - link
In general, they perform fine for light & general user scenarios, but IOPS suffers.In SM2246XT product brief, random reads are quoted at 28,000 IOPS & random Write at 65,000 IOPS (120GB SSD with Toshiba 19nm MLC).
Both Sandforce & SM2246XT are only used with MLC NAND since they were not design to work with TLC ones.
The IOPS drop on a theoretical SSD controller without external dram & working with TLC NAND will be much worse I presume.
Samus - Wednesday, March 30, 2016 - link
Any TLC platform without DRAM or an SLC caching mechanism is going to burn out the NAND; the wear leveling will be off the wall.Pizzahut23 - Wednesday, March 23, 2016 - link
Are we going to get a review of the phison PNY cs2211? It was recommend last month on the recommend budget SSD list. How does it compare to the legendary bx100 which is about the same price? Is it the new go to budget SSD?Billy Tallis - Wednesday, March 23, 2016 - link
I've tested both the PNY CS1311 and CS2211. They won't be the next review I post, but probably the one after that. As compared to the BX100, the CS2211 is very broadly in the same performance class, but its different controller architecture means it has very different strengths and weaknesses.ghanz - Wednesday, March 23, 2016 - link
Hi Billy, are there any plans to review the Sandisk Plus 240gb or/& 480gb?It's probably cheapest MLC drive in lower capacities now I believe.
While it's similar to the Sandisk extreme 500, it will be interesting to see the differences of the same SM2246XT controller on a SATA3 interface instead of USB 3.0/3.1.
It will also be interesting to compare a budget MLC drive with the influx of recent budget TLC drives.