Samsung 840 EVO 500GB and 1TB Full Review - TurboWrite TLC
Introduction and Specifications
Last week, Samsung flew a select group of press out to Seoul, Korea. The event was the 2013 Samsung Global SSD Summit. Here we saw the launch of a new consumer SSD, the 840 EVO:
This new SSD aims to replace the older 840 (non-Pro) model with one that is considerably more competitive. Let's just right into the specs:
The new 840 EVO employs Samsung's 'MEX' controller, where the 840 and 840 Pro used 'MDX' and the 830 Series used 'MCX':
From this slide we can tell the 840 EVO is employing the same TLC flash used in the older 840. The difference here being this new flash is 19nm as compared to the 21nm flash used in the older 840 and 840 Pro.
Specifications and TurboWrite:
Here are the throughput specs, starting off with the main differences between the 840 and the 840 EVO. Note the increased write specs:
Ok, the speeds are much quicker, even though the flash is still TLC and even on a smaller process. How does it pull off this trick? Tech that Samsung calls TurboWrite.
A segment of the TLC flash is accessed by the controller as if it were SLC flash. This section of flash can be accessed (especially written) much faster. Writes are initially dumped to this area and that data is later moved over to the TLC area. This happenes as it would in a normal write-back cache - either during idle states or once the cache becomes full, which is what would happen during a sustained maximum speed write operation that is larger than the cache capacity. Here is the net effect with the cache in use and also when the cache becomes full:
For most users, even the smallest cache capacity will be sufficient for the vast majority of typical use. Larger caches appear in larger capacities, further improving performance under periods of large write demand. Here's the full spread of cache sizes per capacity point:
We will take a close look at how this cache interacts with performance in the pages to come.