Western Digital Black SN850X, 4TB, M.2 Gen4 x4, with Heatsink

Sequential read speed or the mean data reading speed is the most important criterion of the high-speed operation of the SSD. The data from the SSD will be read much more often than written to it because the operating system stores the processed data in the RAM in most cases.

If you want the reading speed of the purchased SSD to exceed the speed of the classic HDD considerably you should choose the SSD with the reading speed of 200 MB/s or above. The additional increase in the performance will be achieved on the account of the data search (SeekTime) which is of much higher level with SSDs than any HDD.

The writing speed is almost as important as the reading speed. Also this parameter determines the performance of the SSD, however, as the writing to the disc happens not as often as the data reading and average user will find it subjectively difficult to distinguish between any speed above 100 MB/s and higher indices, except the cases when the SSD is used in a server, for audio/video recording, etc.

Thanks to the small size provided by the SSD technology the standard size of the discs is 2.5", and it is suitable for an average portable computer. It is possible to install the 2.5" disc in the desktop computer if the transition 2.5" -> 3.5" is used, and this transition can be bought at a low cost at TopPC.fi section"Adapteri". The discs with the format 2.5" + 3.5" have this transition included.

1.8" discs are intended for the ultra-compact class portable computers.

PCI-Express SSDs are intended for desktop computers with a free PCI-Express plug available. This technology in most cases is used for ensuring the performance that exceeds the possibilities of other types of connections.

SSDs with SATAII and SATAIII connection are compatible with the connections of both types in the motherboard. Still, it has to be taken into account that the motherboard SATAII connection can provide maximum about 300 MB/s transmission capacity which can reduce the actual transmission capacity of the SSDs whose reading and/or writing speed exceeds this level to the capacity limits of the SATAII.

The situation is similar with the PCI-Express and SATAIII connection slots. Although the SATAIII standard can provide up to 600 MB/s data transmission capacity there are SSDs with the speed exceeding this limit, in this case the manufacturer chooses the PCI-Express connection slot with a higher transmission capacity. The PCI-Express discs cannot be connected to the portable computer.