(For Geeks Only)
By Joe Callison
5 September 2018

There are many types of computer memory being used these days. It used to be simpler when you had RAM memory and a hard drive. Sure the RAM memory evolved over the years from DRAM to DDR, then DDR2, DDR3, and DDR4, and hard drives went from SCSI or PATA to SATA, then SATA2, and SATA3, but now there are several more new types to confuse us. 

Several new forms of solid-state memory are either supplementing or replacing the traditional hard drives. Hybrid drives retain the rotating mechanical platters, but supplement it with some amount of high-speed solid-state memory that is much faster but still non-volatile when used as a cache to speed up the hard drive data access. Completely solid state drives (SSD) are rapidly replacing hard drives, at least for booting the main operating system, and for more and more of the other data storage as the cost per GB drops and capacities increase.

Small notebook computers and tablets often use eMMC memory to replace the hard drive, which is a form of flash memory and is typically soldered directly to the logic board. The HP Stream tablet computers are one example. These usually have a fixed amount of memory that is not practical to replace or upgrade, so some people were frustrated to learn that their cheap computers with 32GB of flash memory were often not enough to accomplish Windows 10 feature updates in the usual manner where the previous Windows 10 version is retained in a windows.old folder. More often computers, especially laptops, are using M.2 slots on the logic board to hold solid-state memory modules that can be SATA or PCIe NVMe depending on the type of bus the M.2 slot is connected to, the latter being much faster. These types of memory cost a little more than an SSD but take up less space and are ideal for thin laptop designs.

Flash memory-type SD slots are often provided that can be used as supplemental disk storage, although they are not very speedy. SD memory, commonly used in cameras and smartphones, has speeds defined by a Class number from 2 to 10, higher being faster. Newer formats of SD cards are UHS speed class or Video speed class. The type and capacity of SD card must be compatible with the device you are using it with.

Many of the small laptop and tablet computers are using RAM memory that is soldered to the logic board and so, like the eMMC memory, is not practical to replace or upgrade. A few have part of the RAM included on the logic board and a slot for additional RAM to be added.

With so many different forms of memory being used in computers now, some replaceable and some not, purchasing a computer requires investigation into what is being provided and how or if it can be accessed in order to not be surprised after purchase. The same goes for batteries!

Posted by Joe Callison

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