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Would this make the term 'disk drive' a slight misnomer?

Also, I thought RAM was equivalent to the term 'volatile' memory, but apprently 'hard disk drives' are also RAM and not ROM... any clarification is appreciated!

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Nice question! I think a lot of people get the terms confused. –  Diago Sep 30 '11 at 11:18

2 Answers 2

up vote 11 down vote accepted

Yeah, the terms have become a bit messy.

The term "drive" originally referred to the thing moving the storage media - like a floppy drive is something you put a floppy disk into and it spins it. A tape drive is the thing that drives the tape around the read-write heads. Originally with a hard disk, the drive was separate from the disk platters - you used to load the hard disk into the disk drive. Now, the drive is built-in. So a hard disk drive is referring to both the disk and the drive at the same time.

Now we have "solid state drive" or "solid state disk" which contains no drives and no disks.

These are storage media, ie where you keep applications and files.

RAM is volatile memory (usually) and where an application or the OS is loaded in order to run it. It is based on silicon chips rather than magnetic media.

A hard disk would never be referred to as RAM. The only time these two ideas get close is where an operating system might pretend it has extra RAM than it really does by using part of the hard disk as "swap" or virtual ram. Basically, the OS will swap unused contents of RAM to disk to free memoryfor other applications, then swap them back again when they are needed.

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Or when you're using a RAM-based SSD. –  Ignacio Vazquez-Abrams Sep 30 '11 at 4:16
Of course, hard drives might also contain volatile memory used for caching data to be read or written, as well as ROM chips with drive firmware. –  user55325 Sep 30 '11 at 4:16
I can't wait for the day where RAM has a little hard disk in it that it backs itself up to when it senses power loss. –  Paul Sep 30 '11 at 5:34

Would this make the term 'disk drive' a slight misnomer?

Since there is a (bad) tendency to shorten "adjective noun" names to just the "adjective" (e.g. "remote control" becomes "remote", "IP address" is "IP", "passive cooling" is "passive"), the term "disk" is often just short for "disk drive".

"Drive" used to be synonymous with "transport", the electromechanical device that would rotate/spin and read/write the media. Magnetic tape drives and disk drives are two types of transports.

The disk drives were as large as a washing-machine, had a hefty motor and read/write electronics, and used large (14") removable, multi-platter disk packs, aka "storage modules". The concept of mounting a filesystem comes from the physical act of mounting (installing) a disk pack in a drive.

The IBM Winchester disk was the first disk pack to incorporate the R/W reads with the disk pack (instead of part of the disk drive). The trend away from removable disk platters to fixed platters within the drive was under way with 8" hard drives. PC users only know of hard drives with fixed (non-removable) platters. Hence the terms "disk" and "drive" have evolved in to equivalent terms. In addition, a disk's attribute of storing a large amount of data leads to hijacking of the term for other mass-storage media such as "RAM disk" and "solid-state disk".

Also, I thought RAM was equivalent to the term 'volatile' memory

RAM is the acronym for random access memory. There is no assumption or characterization about volatility. In fact, if you're old enough to remember, computers (but not PCs) up to the 1980s used (non-volatile) ferrite core memory. Battery-backed static RAM is another way to implement main memory that is non-volatile. It's the (now prevalent) use of dynamic RAM for main memory and its attribute of volatility that leads to the faulty association of RAM and volatility.

  • RAM is (commonly) implemented by dynamic RAM.
  • DRAM is volatile.
  • Therefore RAM is volatile. Improper (if not faulty) syllogism!

apprently 'hard disk drives' are also RAM and not ROM

These are not the same devices. RAM and ROM are memories which are usually connected to the processor by an address and data bus. A hard disk drive is a peripheral which has the function of providing mass storage; it is addressed and performs data transfers in blocks (aka sectors).

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