What Role Do SSD Components Play – Learning To Run With Flash

Today’s consumer is a much smarter breed than we all were yesterday.  The simple fact that SSDs are faster, totally silent, create less heat, are significantly more impact resistant and provide longer laptop battery life than the hard drive, just isn’t enough.  Today’s consumer wants to know how this is possible and why. Our introductory two articles in the ‘Learning To Run With Flash’ series spoke to our opinion of the relatively slow consumer SSD transition and our thoughts as to why.  We then started the ball rolling with ‘What is an SSD’ in our effort to provide a wider base of knowledge with respect to solid state drives and their importance in today’s PC.

TYPES OF SSDs

This article will describe the components of the solid state drive and the role each plays.  Although we will cover the types of SSDs in more detail in a later article, it merits mentioning that there are several form factors of SSDs available to the consumer.  These include the notebook form factor SSD that matches the exterior dimensions of a hard notebook hard drive at 2.5” wide, mSATA SSD, PCIe SSD, and the newest and smallest form factor which is the M.2 SSD.

Although most parts are consistent in all SSDs (PCB, controller, memory, interface), we will describe that which the consumer is most likely to see, the notebook SSD.  Originally available in a thickness of 9.5mm, today’s notebook SSDs are typically only 7mm thick to allow for ultra book installations and may include a ‘rubber spacer’ to allow it to fit notebooks that require that 9.5cm width.

An SSD is made up of several components that each play a significant role in providing vastly increased protection, performance, and durability, in comparison to a hard drive.  These components consist of the exterior casing, a printed circuit board (PCB), controller, NAND flash memory, and an interface.  We may or may not see other components such as DRAM cache memory or power capacitors in an SSD that we will speak briefly to in this a briefly as well.  All of the components of which we just spoke are seen in this shot of the new Crucial M550 SSD:

EXTERIOR CASING

Typically a SSD contains a two-piece exterior aluminum casing, secured by four screws of which one may be covered by security tape to avoid tampering.  The exterior casing is used to protect the interior components and may also serve the purpose of providing heat dissipation from internal components. In our recent report on the Crucial M550, this was evident as there was a rubber thermal conductor present on the inside cover that pressed up against the controller when the SSD was assembled.  Heat would move from the controller to the exterior aluminum casing, via the thermal pad, where it was dissipated.

PRINTED CIRCUIT BOARD

The printed circuit board (PCB) is most often screwed into the interior case of the SSD and contains the SSDs components.  It is common on every SSD and it’s most important role is to provide the access for data to travel via interface, controller, memory and cache.  mSATA, PCIe and M.2 (NGFF) SSDs would normally not contain an exterior casing and the PCB is easily identified by its standard green color (as seen above)

SSD CONTROLLER

The SSD controller is the heart and soul of the SSD and the engine to data travel and proper SSD function.  It is square in appearance and placed between the memory and SATA interface connector by which a cable runs to the PC.  It is also responsible for such things as data transfer speeds, ensuring that the SSD has a long life span through even distribution and deletion of data to memory cells, as well as encryption and security of the SSD.

Many may have heard that controllers can be 4 or eight channels and this impacts directly on performance.  Consider that a channel represents a road and each memory module a storage facility.  If we were to have eight trucks moving a load of information simultaneously to eight locations for storage, this could be accomplished faster than a single truck making several runs to complete the trip.  This is exactly how channels work and more channels, accompanied by more memory packages, means a faster machine.

SSD controllers have typically required much less power to transfer data, in comparison to a hard drive, thus improving laptop battery life.  Newer controllers push a step further as they are ultra low power and capable of a new feature called SATA DEVSLP (Device Sleep). DEVSLP is a signal that tells a SATA drive to enter into a very low power state.  Another signal is capable of bringing the SSD out of DEVSLP in order to update things such as OS and e-mail without the system returning to full power.  This increases ultra book battery life significantly with some expected to reach 12-14 hours before a recharge is necessary.