These tests show just how quick the EVO, with its TurboWrite tech, is compared with the top-end 840 Pro series. The £2,300 PCIe KingSpec drive is capable of some incredible peak sequential transfer rates, but its 4K random performance can't come close to what the Samsung 840 EVO 1TB can mange - at almost a fifth of the cost. At £150 for the Samsung 840 EVO 250GB - which has almost identical performance numbers as the 1TB drive - you're really getting top-end performance, at decent capacities, for a great price. While at around the £500 / $650 neither of these drives are particularly affordable, it does mean that the price of the smaller drives in the range get more accessible. The M500 is slightly cheaper, but also slightly smaller - with a formatted capacity of around 890GB versus the 840 EVO's 931GB - and can't keep up with the faster Samsung drive in any of our performance metrics. It's this random performance that just gives the 840 EVO the edge over the competing Crucial M500 960GB drive. That's what's going to really impact your general system performance and responsiveness. The random read performance also doubles, from just over 20MB/s to 41MB/s in the Samsung 840 EVO.įor me, higher random performance is the holy grail for SATA 6Gbps-based drives. The Samsung 840 EVO will hit 110MB/s, making it the most responsive SSD I've ever tested. In terms of write performance the quickest drives I've seen were knocking around 55MB/s, even the PCIe-based KingSpec could only manage around 60MB/s. And when I say high, I'm not messing around. The new Samsung MEX memory controller in the 840 EVO is slightly higher clocked compared with the MDX of the 840 Pro series, and they have done some additional tweaks to ensure the random performance is high. If your OS drive hits a snag somewhere that's when you get stuttering. The quicker they're capable of doing this, the smoother the experience of using your rig will be.
The random 4K speed represents how quickly a given drive is capable of shunting around the small, bitty files that make up the bulk of operating system I/O operations. However, random performance has seen a great boost, dishing up double what previous drives have been capable of. That means, like pretty much every other 2.5-inch SSD around we're locked around the 520MB/s mark for sequential read/write performance. Obviously we're still limited by the stagnant-looking SATA 6Gbps interface, with its 600MB/s theoretical limit. So, what of performance then? Well, in a word: stellar. While this means the 120GB drive has seriously impressive performance much of the time, it is going to be more likely to fill the cache on a regular basis. The 750GB drive has 9GB, the 500GB has 6GB and the 250GB and 120GB drives only have 3GB set aside for TurboWrite.
That cache level doesn't stay so high for the rest of the range though. You're unlikely to write more than 12GB to the drive in general usage, so performance is going to remain high for pretty much all the time you're using it. In this 840 EVO 1TB that's not really something you have to worry about too much as the TurboWrite cache is sitting at 12GB. The drive will then flush the TurboWrite space into the slower areas of the SSD once it goes idle, but if the drive is continually used without letting the cache flush then it will revert to the slower 3-bit MLC speeds. The speed stays at peak levels for as long as the simulated SLC isn't filled up. That enables the drive to write quicker to that area, essentially using it as cache. Samsung is calling this TurboWrite and it classes a certain amount of the drive's capacity as simulated SLC NAND.