laptop/desktop memory/cache/storage space

[Ghost12321]

Oh hi,

 

So I was wondering if someone could explain how memory works on a laptop and/or desktop (if there's any difference). I know there are several sources of memory which all are interconnected but I'm not quite sure how. There's the processor which has a small amount of memory (cache memory?), then there is the solid-state drive memory (flash memory?), then there is the RAM memory, and lastly, the hard drive memory (storage space?). Could you please explain to me what all of these are/do and how they all function together?

 

Thank you in advance.

[StringJunky]

Analogously, the CPU (Central Processing Unit) is your brain and the Random Access Memory (RAM) is the table you are sat at which you can put your data on and the hard-drive is the filing cabinet where you keep your data for long-term storage. Following this analogy through, you can see that the bigger the table (RAM) the more information you can put on it and consequently, the less trips you have to make to the filing cabinet (hard drive) to keep filling the table as your brain (CPU) uses it.

IF the ram is too small and the computation or demands too large (too many apps open), the CPU will create something called 'virtual memory' (VM) which is space allocated on the hard drive that it uses as extended memory. It will swap files that it currently needs between RAM and VM until it has caught up with demand...this is really slow and you will notice long pauses between operations. Analogously, VM is the equivalent of you picking up bits of info that you currently need and putting it in a special folder in your filing cabinet then getting some more info from your cabinet, going back to your table, performing your calculations, taking that back to your filing cabinet and getting the old info out of your special folder, walking back and using that...this cycle will be repeated until all currently pending demands are met.

In terms of speed of access and retrieval, the processor cache is the fastest, followed by RAM then the hard drive. The function of the processor cache, which is embedded with the CPU unit, is to pre-fetch information that the CPU guesses that it's going to need next. If it gets it wrong it dumps that info and gets the right info from RAM.

The SSD is just the latest form of hard drive that has no moving parts, unlike the currently predominant mechanical hard-drives, and because their is no physical movement of components in it to read and write data it is much faster to deliver data into RAM.

Cache memory and RAM are classed as 'volatile', which means they only hold data whilst the OS is running. Mechanical HD's and SSD's hold data regardless of whether it's running or not. Conventionally, only the CPU cache and RAM are called 'memory'; the HD and SSD are called 'storage'.

Edited December 16, 2012 by StringJunky

[Ghost12321]

Thank you for the reply and the great analogy, StringJunky.

[StringJunky]

That's ok.