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Memory (RAM) and Hard Drives explained (for noobs)

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Memory (RAM) and Hard Drives explained (for noobs)

Postby HouseCrowd » Wed Jun 01, 2005 8:19 am

I often get asked when building/repairing/upgrading PCs, what the functions of memory and the Hard Drive are in a PC, and I find many newcomers often confuse the two things.

I usually use the following analogy (verbally) to explain, but recently had the need to put it into type, so I thought I'd share it, in the hope that it will clear the confusion up for a few more people, so here goes:



Imagine you're a worker, sat at a desk, processing paperwork, with the end result of each completed operation being entries which you make in some sort of ledger book directly in front of you.

On your desk, and within easy reach, you have an 'in-tray' with paperwork waiting to be processed, and in the office you are sat are rows of filing cabinets containing even more pending paperwork.

In this analogy, the worker (you) are the processor, aka the CPU (Central Processing Unit), and the workspace/book directly in front of you is your Cache memory. The Cache memory is usually an integral part of the CPU, and therefore can not be upgraded without replacing the CPU itself. Whilst the cache represents a very small amount of memory compared to other memory in your PC, it is very fast, partly because of its close proximity to the processing operations. Your desk space in this analogy represents the computer's memory (RAM), and the filing cabinets the Hard Drive.

When you've finished with the paperwork directly in front of you (i.e your Cache area), you take some more work from your 'in-tray', or your desk. This of course involves reaching out for it, and transferring it to your 'cache area' once again. Whilst within easy reach, this still adds a little time to the processing of the paperwork, since it's not immediately in front of you. This storage area represents your system memory (RAM) in this analogy. This is still fairly fast memory, but not as fast as the immediately accessible cache memory, and whilst much larger than the storage capacity of the cache, its capacity is still rather limited.

Another thing to understand is that both these types of storage space are 'volatile', i.e they do not retain data after power-off - you can imagine this as a clearing of your desk every time you've finished working. In order to 'reload' your desk with work when you start again, you need some 'non-volatile' storage area, which can store and retain large amounts of data/work. This is were the Hard Drive (or in this analogy, the filing cabinets) comes in. Whenever you start work, or run out of work on your desk, you go to the filing cabinets for more. Of course this takes even more time, since it involves getting out of your chair, so with each visit to the filing cabinets you grab a large stack of paperwork - enough to fill your desk again - so as to reduce the amount of time spent going back and forth for more.

In this analogy, clearly distance is what governs the speed at which new data can be accessed, though in the reality of computers there are many other factors. Still, the concept should still help give a basic understanding of the processes involved. Given that, there are several things that can be done to ensure the work is done more quickly:

1)
We could bring the work closer to the worker: This could be done by moving in-trays or filing cabinets closer to the worker (CPU) which would represent installing faster memory, and/or a faster Hard Drive.

2) We can use a bigger desk or in-tray: More desk storage means not having to get up to go to the filing cabinet as often. This would represent installing more memory (RAM), and would generally increase the speed of most operations, though there are times when the work is mostly Worker (CPU) intensive that would not benefit from more desk space (memory). Also, there is an upper-limit where further increases in the size of the memory/desk have little effect on speed.

3) A faster Worker/CPU: This seems the obvious solution, but of course it only speeds up the actual work being processed, having little effect on the fetching of that work. Whilst a faster Worker (CPU) will almost always increase processing speeds, the gain can be very marginal, especially if there is a shortage of work space (memory). For example: Doubling the speed of the Worker (CPU) may only increase the speed of the system as a whole by a small percentage if there are lots of trips back and forth to the filing cabinet (hard drive) due to a lack of desk space (memory/RAM).


In summary: plenty of memory and a fast hard drive are an important factor in the speed of any system, and in day-to-day use (Booting up, opening/closing programs, transferring files, etc) they can have a greater impact on overall performance than processor speed will. However, there is no directly proportional relationship with system speed, and any differences in speed will be largely dependant on the type of processes being performed. The CPU speed, on the other hand, does have a direct relationship with overall speed, but it may only become apparent when performing CPU intensive work, such as graphical functions, or other heavily mathematical processes.


Please feel free to add comments, or rip it apart! :P
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Postby LxBeast » Wed Jun 01, 2005 8:24 am

Nice analogy HC!

Should be helpful for those new to hardware. [RAM/HDD's]
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Postby ilbozo » Wed Jun 01, 2005 1:34 pm

Nice work HC. one :mrgreen: for you!
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Postby johngalt » Fri Jun 03, 2005 3:30 am

Nice analogy. I think it is better than my atetmpts at explaining the difference.
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Postby ROYGBIV » Sun Jul 10, 2005 11:49 pm

Thanks for the post HC. Although I understand all this stuff I really liked the analogy. I think I will start using it when my buddies ask me the same question, if you don't mind :).
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Postby Michael Jackson » Mon Jul 11, 2005 12:28 am

I would like to say great job, however there is nothing in the universe I hate more than the word "whilst", and you used it about 4 times. It seems to be a tech person's favorite word.

I had to jam a pencil, which I found in my desk, into my brain to stop the pain.

So, thanks for giving the uniformed some info, but now I have a headache.


:?
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Postby Assyrian » Mon Jul 11, 2005 1:43 am

nice HC, 10 points. 8)
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Postby SlyckScratch » Mon Jul 11, 2005 5:43 am

Every forum needs a techie - and Slyck has a really good one. Thanks HC

Michael Jackson wrote:So, thanks for giving the uniformed some info, but now I have a headache. :?


Whilst people in uniform might find the guide useful, the uninformed will more so :lol:
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Postby HouseCrowd » Mon Jul 11, 2005 8:00 am

Michael Jackson wrote: however there is nothing in the universe I hate more than the word "whilst", and you used it about 4 times. It seems to be a tech person's favorite word.



:lol:

Whilst we're on the subject of irritating words, 'however' has to be high up my list! ;) :lol:
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Postby Psycho Ced » Mon Jul 11, 2005 12:10 pm

lengthy; but you are from the UK ... :twisted:
Makes great sense. We expect at least one of these a week from you, from now on! :wink:
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Postby zbeast » Fri Sep 23, 2005 12:47 pm

Great little tech note.

Ram (data goes away when you turn the power off)

Hard drive (data goes away when you least expect it.) :)
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Postby HouseCrowd » Fri Sep 23, 2005 2:55 pm

:lol: :lol: True!! ^^^
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Postby Mrs. 2p » Mon Jan 02, 2006 8:26 am

never got around to thanking you for this, HC, great post! Will be extermely helpful to those just starting off.

Would you mind completing it with a bit of info on RAM (DDR, DDR2 and all the other initials I can't remember), as well as the L1 and L2 memory caché in CPUs? (or whatever it's called) That's where I'm getting stumped. What RAM should one go for in the various scenarios? How much, if any, L1/L2 caché does one need and what for?
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Postby SlyckChuck » Mon Jan 02, 2006 8:30 am

Nicely done HC. You might just get promoted to newbie's guide to computer improvement. I always thought of the idea to do a cover all section or thread to help those to make the most of their computers!!
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Postby Nick » Mon Jan 02, 2006 8:39 am

Not a bad idea, I second that.

And for tyhe record, I think HC has the rare gift of being able to couch his explanations in a manner that is neither condescending nor OTT. Nicely put.
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Postby nJectid » Wed Apr 12, 2006 3:37 pm

zbeast wrote:Great little tech note.

Ram (data goes away when you turn the power off)

Hard drive (data goes away when you least expect it.) :)



lol, i love it. :lol:

i hope that some computer noobs come across this so they will understand the concept of volatile vs non-volatile memory. :roll:
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Postby franc » Fri Aug 04, 2006 1:42 am

thanks for the info
quick questionthough, how do you know how much cache memory you have? (that ledger book thing in your analogy)
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Postby HouseCrowd » Fri Aug 04, 2006 6:44 am

franc wrote:thanks for the info
quick questionthough, how do you know how much cache memory you have? (that ledger book thing in your analogy)


The cache is integral to the CPU, so if you know which CPU you have you could either look up the manufacturer's spec, or otherwise use a tool like CPU-Z.
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Postby franc » Fri Aug 04, 2006 1:14 pm

thanks
i'll try cpu-z
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Postby Ratt » Thu Sep 21, 2006 5:16 am

More ram is always good, but how much virtual memory do you recommend? It's insane how many differing opinions you hear on the subject of pagefile size...
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Postby HouseCrowd » Fri Sep 22, 2006 5:34 am

Well virtual memory space is usually dynamically allocated, so there's really no need to set a fixed size for it. Besides, the whole point of making sure that you have sufficient RAM is to minimise the times that virtual memory is used/needed.
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Postby Ratt » Fri Sep 22, 2006 6:08 am

HouseCrowd wrote:Well virtual memory space is usually dynamically allocated, so there's really no need to set a fixed size for it. Besides, the whole point of making sure that you have sufficient RAM is to minimise the times that virtual memory is used/needed.


Sure, but for a long time people were pushing fixed virtual memory (setting an identical minimum and maximum, like 1 gigabyte for instance). And back when defragmentation could actually slow down older systems, that was probably a good idea. Matter of fact, I still do it, even though I know it makes no real difference now.

And then there was the idea of putting the pagefile on a different drive/partition. Again, not so useful anymore.

Then you had guys with lots of ram who tried disabling the pagefile altogether. The theory being that if Windows doesn't need to write from the ram to the drive, everything's faster. One problem with that: eventually Windows goes bugfug crazy...it is designed to have a pagefile.

(There is a way around that, but it's complicated: creating a ram-drive, which is like a separate partition but inside the ram, and putting the pagefile there. Never tried that myself.)

As you can see I've looked into the issue a bit before, and as I said I found much confusion...
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Postby HouseCrowd » Fri Sep 22, 2006 6:24 am

Very true. There are a lot of schools of thought on the best way to configure it, but like you say it makes little difference now, since large amounts of RAM are very cheap these days, making such tweaking methods pretty much redundant. Back in the days when VM was an important factor in the performance of the PC, I would generally go down the separate physical drive route myself, if that were an option (there's little to gain from putting the pagefile on a different partition of the system drive). As far as size goes, I think it's best to retain the dynamic sizing methods whilst ensuring that the settings reserve enough space to ensure that it isn't being resized too often.
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Re: Memory (RAM) and Hard Drives explained (for noobs)

Postby Mytheroo » Tue Aug 26, 2008 10:45 am

I guess L1 cache is the info the worker is holding in his mind while doing the calculations, and L2 is the ledgerbook where he/she jots down his/her working
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Re: Memory (RAM) and Hard Drives explained (for noobs)

Postby HouseCrowd » Tue Aug 26, 2008 11:55 am

I avoided breaking the cache down in the analogy to keep things a bit simpler, but yes, if you needed to explain the differences between Level 1 and 2 cache, I guess that would work, since L1 cache is generally faster than L2. :)

I think you might run out of comparisons though if you wanted to use the analogy to explain Level 3 cache ...
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