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Are hard disks, CD's and DVD's RAM based?

1Devilsadvocate
Posts: 1,518
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10/31/2013 6:39:06 PM
Posted: 3 years ago
According to Wikipedia,
"Random-access memory (RAM /r"m/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore, the time to access a given data location varies significantly depending on its physical location."

My text book says the opposite, now I know there are errors in Wikipedia, but it strikes me odd that there would be such a blatant mistake on a common/basic topic.

Is this indeed an error on the part of Wikipedia or my book, or am I just missing something?
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themohawkninja
Posts: 816
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10/31/2013 8:00:02 PM
Posted: 3 years ago
No, while they all work off of the same principle, they aren't RAM.

As I understand it, RAM works off of programmable logic gates that hold a 1 or a 0 based of what the transistor is set to via an electric current.

Hard drives, CDs, and DVDs work by having really, really tiny dips in them, and the way that those dips affected by the laser-writer in the disk drive (or in the case of your hard drive, the laser-writer inside the drive itself) determines whether it is a 1 or a 0.
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vbaculum
Posts: 1,274
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11/1/2013 6:47:28 PM
Posted: 3 years ago
At 10/31/2013 6:39:06 PM, 1Devilsadvocate wrote:
According to Wikipedia,
"Random-access memory (RAM /r"m/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore, the time to access a given data location varies significantly depending on its physical location."

My text book says the opposite, now I know there are errors in Wikipedia, but it strikes me odd that there would be such a blatant mistake on a common/basic topic.

I guess it's hard to tersly express a distinction like that.

Wikipedia is conflating the concept of "access" (with RAM) with "reading" and "writing" (with storage devices). So the statements are both true but they don't contradict each other. For example, HDD are "accessed" in random order all the time, but reading and writing is consecutive. Actually, as far as I know, the same is true of RAM.

The reason RAM is faster than long-term storage devices is because the former is purely electrical, and the later is partly mechanical: the actuator and platters in a HDD can only move so fast before they break; RAM can be accessed purely electrically so it's much faster. This is my basic understanding anyway.


Is this indeed an error on the part of Wikipedia or my book, or am I just missing something?
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vbaculum
Posts: 1,274
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11/2/2013 1:46:34 AM
Posted: 3 years ago
At 10/31/2013 6:39:06 PM, 1Devilsadvocate wrote:
According to Wikipedia,
"Random-access memory (RAM /r"m/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore, the time to access a given data location varies significantly depending on its physical location."

My text book says the opposite, now I know there are errors in Wikipedia, but it strikes me odd that there would be such a blatant mistake on a common/basic topic.

Is this indeed an error on the part of Wikipedia or my book, or am I just missing something?

http://en.wikipedia.org...
"If you claim to value nonviolence and you consume animal products, you need to rethink your position on nonviolence." - Gary Francione

THE WORLD IS VEGAN! If you want it
slo1
Posts: 4,308
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11/4/2013 9:29:07 AM
Posted: 3 years ago
At 10/31/2013 6:39:06 PM, 1Devilsadvocate wrote:
According to Wikipedia,
"Random-access memory (RAM /r"m/) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore, the time to access a given data location varies significantly depending on its physical location."

My text book says the opposite, now I know there are errors in Wikipedia, but it strikes me odd that there would be such a blatant mistake on a common/basic topic.

Is this indeed an error on the part of Wikipedia or my book, or am I just missing something?

your text book is wrong. RAM is made up of cells. It is one transistor and one capacitor and that cell can hold a 1 or 0. The cells are in a row column format and as long as know the row and column you can access it in any order.

Versus hard drive it stores data in sectors. Since there is a physical arm moving to various sectors it will store data in particular order.

If you think of Windows and defrag. That happens because a old file in a sector(s) gets deleted. It is now open, so if a new file gets saved it will get written to to first open sector and if does not fit, it will go to next open sector. It quite frequent that the file gets split up, meaning it is not stored in consecutive sectors.

When a lot of files are split up it becomes slower when retrieving the file because it has to read every sector to see if the next portion of the file is in that sector until it finds last portion of the file. A defrag will take files that are split up and rearrange them to consecutive sectors.
JesseR
Posts: 18
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4/23/2014 1:17:38 PM
Posted: 2 years ago
Well hard drive (HDD/Hard Drive Disk) is what permanent memory is stored. when it comes to the optical drive no, ram does not play any role or interacts at all. RAM is just data that is cached and will be erased upon shutting computer off.
BradK
Posts: 475
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5/25/2014 10:51:26 AM
Posted: 2 years ago
RAM can be manipulated when running a program. ROM can't.

Though, practically, you can manipulate ROM. They are both memory, but RAM is meant to be manipulated and ROM is meant to be stored.
SemperVI
Posts: 294
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5/27/2014 8:02:48 PM
Posted: 2 years ago
Short answer - No.

It's pretty basic, RAM is your computer memory and is considered volatile. Meaning it is temporary. You turn the computer off and whatever information was temporarily stored in RAM is gone forever. Harddisks, CDs and DVD is storage. The information on these storage mediums will end up in RAM when you need to access it, but it is merely a marshaled copy of what is stored on the storage medium.

RAM has no moving parts and is much easier and faster to access. The data you have in RAM is solely based one what your computer is access at that time. When you execute a program, that program is temporarily stored and accessed in RAM while you use that program or associated files.
RoyLatham
Posts: 4,488
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6/7/2014 10:05:33 PM
Posted: 2 years ago
The Wikipedia article is correct. The distinguishing feature of RAM is that each piece of stored data is accessed in the same amount of time. HDD, CDs, DVDs are not RAM because how long it takes to access data depends upon the position of the media when the data is requested. The disk must turn until the data is under the read or write head. It might happen to be under the head, or it might require almost a complete revolution of the disk. It may take a very long time to advance a tape to the desired position.

Whether the storage is volatile or not is a separate issue. Flash memory is RAM that holds data when the power is removed. The SD chips in cameras are RAM that is not lost when power is removed, as are SSD in computers.

At the start of computer technology delay lines were used instead of disk. That's volatile memory that is not random access. The data was lost when the delay line was powered down.