Since we have never seen what components are being used inside the Mushkin Callisto SSD series we opened up our 60GB Callisto drive to see what the
internals look like. We found it interesting that the Callisto didn’t have a warranty sticker on it, so we opened up without having to worry about breaking the seal.
After removing the four small Allen head screws that hold down the Callisto Series cover we were able to lift off the cover and
see what makes this little SSD tick.
Here is a closer look at the main component side of the PCB where you
can make out eight Intel 34nm MLC NAND Flash memory chips and the SandForce SF-1200 series controller that is being used on this Solid-State Drive.
Flipping the PCB over we can take a look at the other side, which is
bare and has just eight more Intel MLC NAND memory chips on it.
The heart and soul the Callisto is the SF-1200 series controller seen
above. Some companies have started to market their drives as having a SF-1222 controller as it sounds newer. The Mushkin callisto has the SF-1222 as that is the specific name for this controller and it is part of the SF-1200 series of controllers. As we noted, the Callisto doesn’t have any cache chips on it
as that is because the SandForce controller itself is said to carry a
small cache inside that is a number of megabytes in size. Inside the
controller there’s also the Tensilica DC_570T CPU core; this is used in
both the SF-1200 and SF-1500 models. This controller includes support
for all the latest features like native TRIM support. Mushkin claims maximum
read/write performance of 285/275 MB/s with their revision 3.0.9 firmware. The interesting thing about SSDs with the SandForce controller is that performance doesn’t vary with capacity size. A 60GB, 120GB and 240GB Callisto have the same speed ratings.
The Callisto features Intel 29F32G08AAMDB MLC flash memory.
In total there are 16 chips and each IC is 4GB in density. That adds up to 64GB of storage space, but only 55.8GB of it will be usable space! The ‘hidden’ capacity is used for wear leveling, which is crucial to keeping SSDs running as long as possible. Mushkin is using less over-provisioning than some companies as they reserved just 13% of the MLC NAND for wear-leveling. SSDs with the Idilinx Barefoot controller only reserve 7% for wear-leveling, so they feel that 13% is more than enough. Mushkin told us that with the SandForce firmware at 13% in combination with the much lower write amplification compared to other controllers due to Sandforce’s proprietary techniques, that they are not too worried about reliability. Client usage patterns typically involve fewer writes than enterprise use, so that’s why you see less over-provisioning on client drives. Remember, the SF-1500 controller was supposed to be for enterprise use, which is why it had 28% of the drive reserved for wear-leveling.