Last week we published a review of the new Samsung 840 Pro SSD, which turned out to be the fastest SATA 600 SSD we had seen. We mentioned in the article that Samsung was also planning to release a more affordable series of SSDs based on the new MDX controller. The 840 series will succeed the 830 series, and comes in 120, 250 and 500 GB versions. Hardware.Info tested the Samsung 840 250GB model.
The new 840 series is built around the same MDX controller that the 840 Pro SSDs have, called the Samsung S4LN021X01. Just like the MCX controller from the 830 series, the new MDX controller is based on three ARM cores. These are 300 MHz Cortex-R4 cores, instead of the 200 MHz ARM 9 cores in the older MCX controller, so there clearly is more processing power in the new controller. Together with a number of other improvements, this should lead to increased performance. That SATA 600 is supported is a given, and TRIM is also supported.
Like the previous generation, the new Samsung controller employs foreground garbage collection. This means that while the SSD is performing new tasks, the organisation of data is optimised. The SSD doesn't need to wait for a period of inactivity. Samsung claims this will ensure high performance even after an extended period of use.
The type of flash memory has been changed as well for the 840 SSDs. As far as we know, the Samsung 840 is the first SSD to have TLC memory (Triple Level Cell). Now each memory cell can store three bits: 000, 001, 010, 011, 100, 101, 110 or 111. It requires about 30 percent less surface area than the previously-used MLC chips. While this doesn't immediately translate to lower consumer prices, it's likely it will in the future.
The transition to TLC chips does raise some questions. While Samsung has not said anything on the topic, it is generally known that TLC chips can be overwritten much less frequently than the traditional MLC chips, which store two bits per cell. With the current generation 2x nm chips, cells in MLC chips can be overwritten about 3000 times before they are unable to process new data. For TLC chips that limit is reportedly around 750x. So is this a big deal? For the typical consumer it is not. However, for (semi)-professional users or people that use their PC very intensively, it could potentially cause problems.