HOW TO READ SPECIFICATION OF SSD

Computer hardware has been watered-down into a marketing game of bigger numbers, new, obscure specifications, and unexplained benchmark ratings, generally leaving consumers to fend for themselves. As we did in our GPU Dictionary, we'll break-down the very basics of SSD specs and take a look at how, on the top-level, SSDs work. Understanding how to read SSD specs is easy: As a consumer, there's no reason to read through pages-upon-pages of white papers to understand how electron tunneling works (but it is really cool) solely to buy a solid state drive, but there are a few primary numbers you should be concerned with (and a few to ignore).

Solid State Drives have been on my mind since the flooding in Thailand offset spindle-based prices, so let's delve into what to look for in one. As an add-on, I'd recommend also looking at our guide that discusses SSDs and gaming.

 

Common Specifications

For starters, we'll take a fairly common SSD from Newegg to look at its specs, then drill-down into what they mean: in our example, we'll use Mushkin's Chronos SSD.

Memory Components: See Also: SLC vs. MLC vs. TLC. These three acronyms, fully-defined as "single-level cells," "multi-level cells," and "triple-level cells," devise the methodology and technology that is used for flash memory-based drives. The 'level' determines how many bits are stored per cell, with more bits per cell correlating with more storage at a diminished cost (but less stability). Single-level cells store 1 bit per cell, multi-level cells store 2 bits per cell, and triple-level cells can store 3 bits per cell, with triple-level cells costing about 30% less than what we're used to now. It's much more complex than that, but that's the groundwork - Anandtech has an amazing explanation of these from a more mathematical and in-depth level, if that interests you.

Why is the cost less, though? Because the fabrication location (we explained how these work in our 'where was your CPU born?' post) can output more silicon dies per silicon wafer, the yield-per-wafer is higher and cost to the fab plant is lower, which equates lower prices for consumers. There is a down-side, though: MLC and TLC technology is more volatile and less stable, normally resulting in slower overall speeds than SLC technology, which is faster, but is a higher cost-per-gig. There are numerous countermeasures to MLC and TLC instability, though, so don't avoid them merely on that. SLC is preferred for high-performance systems that are required to have reliable up-time and availability, whereas MLC is quite acceptable for normal users (even to include gaming enthusiasts). Once more, for good measure:

SLC: More stable, reliable technology that often costs significantly more per gigabyte.

MLC: The most common technology used in consumer drives; normally a bit less expensive per gigabyte.

TLC: The least expensive, but also brand new to the consumer market. It's not quite ready for us, yet, and is also less reliable over longer periods of time.

NAND Tech	Cost per GB*	Advantages
SLC	$3.00	Reliability
MLC	$0.90	Compromise
TLC	$0.60	Capacity

* = Averaged figures based on OCZ projections (OCZ will be the first to deliver TLC SSDs to the consumer market).

So what does it all really mean? Not much -- if you're a normal gamer, you're probably going to be pretty forced into an MLC drive.

Transport Interface: This part is familiar ground for many of us: The transfer interface of SSDs is typically seen listed as SATA II, SATA III, or PCI-e. The last two are much faster than SATA II -- but by how much? Here's the maximum bandwidth per 'pipe:'

Interface	Maximum Bandwidth
SATA II	3Gb/s (384MB/s)
SATA III	6Gb/s (768MB/s)
PCI-e 2.0 x4	20GT/s (2GB/s)
PCI-e 2.0 x8	80GT/s (8GB/s)

Quite a difference! That's the maximum bandwidth, though - it doesn't guarantee you'll use much of it. Just because a SATA III interface can transfer up to six gigabits (or 768MB) per second doesn't mean your device can. Though I'm certain many of you know this, it's important to point out that a 'little b' means "bit," whereas a 'big B' means "byte" (8 bits in a byte).

In general, and going forward, putting an SSD on a SATA II interface is limiting your options: SATA II can only transfer a maximum of 384MB/s, so anything above that number goes to waste. PCI-e SSDs are an interesting bit of technology, though -- they're still catching on, but in general, they're for those with a lot of money. If someone asks you, "What's your budget?" and you answer "I'm the Batman," then PCI-e is a great option for you. For the rest of us, there's SATA III.