Basic components

Basically an SSD consists of a case, a print circuit board with a SATA interface, NAND flash memory, often a DRAM chips, which works as a cache, a processor and a firmware which is programmed to the processor. In fact PCB, SATA interface, NAND flash, DRAM and processor can be bought by any company, who plans to release an SSD.

So, what is it now that makes one SSD better than another? Where are the differences? Regaring the PCB there are only very few things that can have an impact on endurance and there is no influence of the PCB on performance. Looking a little bit closer at the NAND flash memory shows that there are more things that can have influence on performance as well as endurance of a drive. But in both cases – endurance as well as performance – the influence is very limited. If two different companies buy the same NAND flash at, let's say Micron, they get exactly the same product.



Companies like Kingston, ADATA and OCZ – Companies who buy the components they need to manufacture SSDs – they all cook with water. Which NAND flash a manufacturer chooses for its SSDs depends on the target market they want to address. If a manufacturer wants to have an entry level consumer product, it's very likely that they go for asynchronous MLC NAND flash. If it's a server grade product, where the most important thing is endurance then they will go SLC NAND flash memory.

The DRAM chip, which is used as a cache on SSDs - if one is needed - there are also only marginal differences when it comes to performance and endurance. Furthermore there is only one SSD manufacturer who doesn't need to buy DRAM from another company. It is Samsung. All the other SSD brands you know have to buy DRAM from a manufacturer that owns fabs. No there are two things left: the controller and its firmware. At this point there are companies that do controller designs, like SandForce and Marvell for example. These designs then go to a manufacturing company where the chips are being made from actual silicium. After that these chips are ready to be sold to other companies that pay kind of a license fee to let's say SandForce or Marvell. The controller also ships with a firmware, which in fact is the most interesting piece of todays SSD. Most of the optimizations concerning performance and endurance need to be programmed in the firmware. At the end of the day there is really no SSD manufacturer that makes everything that's needed for a recent SSD themselves. The manufacturer which comes the closest to this point is Samsung but in fact, there SSD controllers are based on three core ARM processors whereas Samsung licenses the ARM designs.



For the controllers themselves it's the case that in most cases they feature a four to ten channel architecture. The individual pieces of NAND Flash memory are then wired to the individual channels. It's becoming really interesting when you take a closer look at how data is actually being written and read on an SSD. And at this is where the firmware kicks in.

Page 1 - Introduction

Page 2 - Basic components

Page 2 - Controller / Firmware / Manufacturer

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