三星SSD840系列的“基本”：250 GB测评

什么使得三星不同于其竞争对手的事实，它生产的所有部分，从控制器固件的SSD NAND记忆体模组。考虑到三星的可靠性方面的优良记录，这可能是一个重大的优势，因为它让三星控制整个生产过程。

MDX控制器，它采用的是840和840 Pro的固态硬盘，使用ARM的Cortex-R4内核，运行在300 MHz和512MB LPDDR2 SDRAM缓存。它的功能包括支持TRIM，耐磨和垃圾收集。我们知道，从840 Pro的审查，这是一个很能干的控制器，但在这种情况下，它有TLC NAND慢。

TLC和耐久性

在这方面可能是有用的一些背景有关的性质的TLC NAND。最耐用的固态硬盘的闪存电路类型是SLC（单级单元）NAND闪存以较大优势。正如它的名字所暗示的，SLC的每个物理存储单元的数据只存储一个比特。 SLC穿非常缓慢，因此，好的高达100,000编程/擦除（P / E）周期。不幸的是，这种类型的内存也更为昂贵的生产，所以只用在更贵的企业级驱动器。

MLC（多级单元）NAND主流品种，采用的是几乎所有消费类固态硬盘，包括840 PRO。与MLC，耐久性经常减少一个数量级相比，SLC，但到底有多少依赖于过度配置，穿流平性和其他因素的影响。但是，它仍然是足够耐用，消费者在几乎所有的使用场景。

TLC（三级单元）增加了另一层复杂性，并进一步减少相当数量的耐久性。因此TLC迄今大多被用在拇指驱动器和内存卡，其中，耐力是不太重要的，由于罕​​见的转移。三星的840是第一台计算机采用TLC NAND的SSD。

据三星内存模块 - 虽然少得多比MLC耐用 - 1000 P / E周期。这是比优质SLC少百倍，但它会仍然意味着，高达256000 GB，你可以写一个250GB的三星840之前，它终于给英寸，这是相当数据，并对于大多数消费者来说，它应该是绰绰有余拖垮您的笔记本电脑或台式机，其余的驱动。

TLC NAND换句话说，对于大多数用户来说可能是一个非问题。此外，供应三星840系列在有限的3年保修，应该减轻最耐用的关注。

定价和供货范围

840系列的建议零售价为：
•120GB - 139.99美元
•250GB - 249.99美元
•500GB - 479.99美元

然而，实际的街道的价格是相当低的。例如，你可以找到一个250GB的840少$ 170在撰写本文时，包括台式机/笔记本安装套件。可选的安装套件包括一个SATA到USB电缆，SATA数据线和电源线，桌面系统和一块3.5英寸适配器支架。还包括三星的“智能数据迁移”软件，为您现有的数据转移到新的驱动器和操作系统。

另一个值得注意的细节是840 SSD是7毫米厚，因此比标准的9.5毫米笔记本硬盘薄。这使得驱动器，适用于某些超极本和其他超薄外形的笔记本电脑，使用的格式。该驱动器还附带一个标准的笔记本电脑硬盘托架SSD进入装修安装垫片。

不像使用无处不在的SandForce SF-2281控制器和其他的固态硬盘，三星硬盘是不依赖可压缩文件，以实现自己的最大速度。英特尔520演示清楚SandForce的供电固态硬盘依靠压缩多少。正如你可能想到的，写入速度是三星840高端驱动器相比，它的弱点。 840 Pro的一样，它也不太一致，而比老的830 SSD写入。

As a stress test we let the IOMix profile run on the entire SSD for 60 minutes. This shoud simulate the performance drop over time in filled SSDs which have been at load for extended periods of time. SSDs with more overprovisioning (dedicated spare area) should have an advantage.

Samsung's SSD Magician software allows the user to adjust the amount of overprovisioning. This essentially means setting aside more spare area  to lengthen the drive's lifespan. Considering the less durable TLC NAND modules used in the Samsung 840, it might be wise to sacrifice some space for a healthier drive.

The 840 series performs very well. They start lower than the 830 series but will eventually outpace them by an average 49 MB/s (840 Pro) and 52 MB/s (840) (830 - 38 MB/s). The Intel 520 series remains in the lead with its 200 MB/s and loses slightly in the IOMix test.

To test the SSDs power consumption we use two multimeters (current and voltage of a 5V wire) on the same PC used for our other benchmarks. Idle power consumption in notebooks should be reduced considerably (to 0.04 W) thanks to DMPI support, but this feature can unfortunately not be activated on our desktop system. The 0.04 W number has however been confirmed by our colleagues at Tom's Hardware.

Compared to the 840 Pro, the standard 840 requires a bit more power to operate on average, but the power consumption is considerably lower than its predecessor the 830, particularly when writing.

To measure the effect on battery life, we installed the SSDs as a system drive in a  precursor model of the Asus N56VM. First we tested the maximum battery life with Battery Eater's Reader test. As opposed to our regular resting procedure, WLAN was left on. In the second test – simulating a higher load – we ran the IOMeter profile IOMix on a small (<10 GB) partition. 

Both 840 drives produce good results, with the regular 840 even performing a bit better than the 840 Pro. However, this is not the case under IO load, where the non-Pro model fares a lot worse. On the other hand, it still comes out ahead of all the other tested SSD except the Intel 510 in terms of battery runtime under load.

Considering that the two SSDs use the same controller, comparisons between the 840 Pro and the normal 840 are inevitable. 

Although it is a cheaper drive in all respects, the 840 still manages to keep up with the 840 Pro in  terms of sequential read speeds, but falls shorts in many other areas - most obviously write speeds, but the 840 is also significantly slower than the 840 Pro in our IOMeter and file copy tests. 

On the other hand, the difference in everyday use should not be overly dramatic. Boot and load times are similar with all modern SSD, something that is also evidenced by the more general PCMark benchmarks.

Another important factor when choosing an SSD is reliability, and here Samsung has an excellent track record. On a more anecdotal note, we have used the Samsung 840 in a production machine for several months, where it still runs flawlessly. TLC NAND should not be a major concern for the average user as it should (theoretically) last for many years.  

Samsung's SSD Magician software is quite useful, and in some ways better than even Intel's SSD Toolbox in that you can assign you own amount of overprovisioning. Setting aside some extra storage space to improve the drive's longevity might be a good idea in this case, to be on the safe side.

As long as Samsung can keep the price considerably lower than high-end drives with better NAND, the 840 series is an attractive alternative. This is particularly true for users who are looking at upgrading to their first SSD at a reasonable cost per GB.