shouldn't HD, CD, etc be called something other than random access?

[dpopiz]

it seems to me that HDs, CDs, and all other types of disc memory aren't really "random access" in the same way that solid state is.
with disc-based memory, it takes longer get to some data than others because the head has to move to correct position and then wait for the disc to rotate around to the right spot. with solid state memory, all data takes the same amount of time to access not matter where it is physically on the medium

 

[AIWGuru]

I'm not sure what context this is taken from but what you stated about SS media is simply not true.
Regardless, the context you were reading this in was probably contrasted to a medium like tape which is SA.

 

[JBT]

I think they call it random access time for the exact reasons that you just said... It a certain amount of time because we don't know exactly where the data is and exactly where the head is and what part of the rotation the disk is at, hence its randomness because we don't know it can take a long time or a short time.

 

[Pariah]

JBT basically got it. It's random access on a hard drive because there actually is a randomness to it. The drive head has to go find the spot on the drive which creates a random seek everytime. With flash or solid state, there is no random access, they have a defined latency, no matter which cell they are getting it is the same delay. When it's predefined, it's not random.

 

[dpopiz]

Originally posted by: Pariah
JBT basically got it. It's random access on a hard drive because there actually is a randomness to it. The drive head has to go find the spot on the drive which creates a random seek everytime. With flash or solid state, there is no random access, they have a defined latency, no matter which cell they are getting it is the same delay. When it's predefined, it's not random.

then why is system memory called RAM (random access memory)?

 

[LethalWolfe]

Random access = You can access the data in any order you want to. For example, you can skip from point A to point Z to point C to point F.

Linear access = You can access the data only in a certain sequence. For example, you can go from point A to point Z but you have to go thru points BCDEFGHIJKLMNOPQRSTUVWXY to get there (you can't "skip" an letters).

Lets look at CDs and casette tapes. If you are on track one of a CD and you want to get to 5 you just "skip" to five or just push "5" on the remote. And boom you are at track 5. If you are on track one of a tape and you want to get track 5 you have to fast forward thru tracks 2, 3 and 4, before you can play track five.


Lethal

 

[Pariah]

Originally posted by: dpopiz

Originally posted by: Pariah
JBT basically got it. It's random access on a hard drive because there actually is a randomness to it. The drive head has to go find the spot on the drive which creates a random seek everytime. With flash or solid state, there is no random access, they have a defined latency, no matter which cell they are getting it is the same delay. When it's predefined, it's not random.

then why is system memory called RAM (random access memory)?

Because that's how the data is accessed. It doesn't have to go through every byte before it, it can be accessed directly. You can randomly pick the byte that is being looked for. You're comparing to different types of random access in the same post.

 

[dpopiz]

ok so what do you call these two types of random access?

there must be some way to differentiate between them because they're so different

 

[LethalWolfe]

As I understand it the "random" in random access doesn't have to do w/the speed at which the data is accessed but in what order the data can be accessed (see my original post for examples). Almost everything computer related in terms of memory and storage is random access because linear access is, by comparision, so freakin' slow.


Lethal

 

[Pariah]

One random access refers to how the data is accessed. As Lethal explains in his post, you have random and linear/sequential access. Basically everything on a computer except tape drives are random access because they do not need to go through all the data before it to get to the data that is being requested. With a tape drive, if the data is at the end of the tape, you have to search through the entire tape before getting to the desired data.

The other random access, is the rate at which the data can be located. As in average random access time. EVERYTHING has an average access time, using a monkey to find a certain lego in a box full of toys has an average random access time. With RAM though, the average random access isn't really random, it's a predefined latency that we know the value of before the search is ever performed.

 

[LethalWolfe]

Ah-haaa...

Thanx for clearing that up Pariah.


Lethal

 

[AIWGuru]

Originally posted by: LethalWolfe
Random access = You can access the data in any order you want to. For example, you can skip from point A to point Z to point C to point F.

Linear access = You can access the data only in a certain sequence. For example, you can go from point A to point Z but you have to go thru points BCDEFGHIJKLMNOPQRSTUVWXY to get there (you can't "skip" an letters).

Lets look at CDs and casette tapes. If you are on track one of a CD and you want to get to 5 you just "skip" to five or just push "5" on the remote. And boom you are at track 5. If you are on track one of a tape and you want to get track 5 you have to fast forward thru tracks 2, 3 and 4, before you can play track five.


Lethal

Lethal Wolfe got it. Everyone else was wrong. It has nothing to do with the time it takes to read something. It's about the way the data is stored. I said this in my first post when talking about these mediums vs tape.

 

[Thegonagle]

LOL! Random access Legos! That brings back memories. As a kid, I used to wake up early some mornings and start playing with Legos. Consequently, I would wake up everyone else in the house randomly ?accessing? my Legos from the big box.