RAM Explaination please

  Andy1991 11:35 25 Aug 2007

I'm trying to understand RAM. And i can't find anything on internet with explaination i understand.
What is the difference between DDR and DDR2. ANd what does the PC3200 number mean. And if i said DDR400 what is that number.
I'm also trying to understand in detail why you loose a certain amount of RAM when 4GB installed.

  Taff™ 11:41 25 Aug 2007

Here`s a good start click here FAQ`s at Crucial. The answer to the 4GB issue is listed on the page.

  Andy1991 11:54 25 Aug 2007

So for that question: Windows can only handle a certain amount of RAM, so, if i had 32 bit windows xp, with 4GB installed, I would only get 3GB in windows. Where does the rest go. and how does 64 bit differ.

  Taff™ 12:01 25 Aug 2007

Re-Read the answer, it does tell you! (What happens is that some of the addressable memory is reserved.....)

64 Bit systems are twice the speed of 32 bit systems and handle the memory differently. Click on the last link on the page which says "see this related FAQ"

  Andy1991 12:19 25 Aug 2007

these sites don't tell me everything, be easier for an actual person to explain it personally. It is a bit basic, and questions keep poping up in my head of why, why, why. I would really like to understand this.
To my head so far: For some reason only if you have the same amount of RAM as your CPU can support, it reserves a certain amount of address space for paging for hardware, only the remaining is accessible by the operating system. is this right? And why only when its the same as the CPU maximum support.

  norman47 12:32 25 Aug 2007

" What is the difference between DDR and DDR2 "

DDR was the first double data ram to be brought out. It's maximum speed was 400Mhz. DDR2 is the newer of the double data ram and it's speed can be as high as 1066Mhz. So the faster ram will give faster performance. It's like using an old 400Mhz cpu, upgrading it to a 1066Mhz cpu will give you better performance. The pin sizes are different for the different dimms ( stick of ordinary ram )but strangely enough are the same for sodimms ( laptop memory ). Though you can not put ddr2 into a ddr slot and vice versa.

  norman47 12:37 25 Aug 2007

" what does the PC3200 number mean."

It's just the model number for the ram, in as much an AMD Athlon 64 X2 4200+ does not run at 4200Mhz, it actually runs at 2200Mhz. So it's the model number.

And if i said DDR400 what is that number. that is the normal speed the ram will run at 400Mhz. It can run slower and some ram can be clocked to run faster.

  Taff™ 12:37 25 Aug 2007

Unfortunately I`m no expert, let`s see if one turns up here!

  Taff™ 12:39 25 Aug 2007

Or How Stuff Works click here

  norman47 12:42 25 Aug 2007

" I'm also trying to understand in detail why you loose a certain amount of RAM when 4GB installed."

A 32bit operating system can just take a total of 4Gb of memory. That is for everything. If you use a seperate graphics card of say 256Mb and have 4Gb of physical memory installed, then you have exceeded the total that windows can handle. It will then cut down on the last stick of memory installed on your computer. If you have 4 sticks of 1Gb it will reduce the last stick. It may take all of the 1Gb or part of it. It even may not boot the computer or give errors untill that last stick of memory istaken out of the computer.

A 32 bit operating system has limitations to the ammount of memory it can take due to 32 bit addressing. A 64bit O/S can, in thoery, take thousands of Gb's of memory.

  Andy1991 15:40 25 Aug 2007

A friend said that RAM PCXXXX number was something to do with bandwidth.
Why is it then I have a 64bit OS, and its cut down my RAM and other report the sam problem, sites are saying that when it is the same as the maximum ur CPU supports, it reserves address space for Physical hardware use, and ht eoperating system has the rest. I also read somewhere to get the full amount you benifit from 64 bit OS somehow. argh. I got my GCSE's two days ago and i'm going to college soon, and i like to understand it before then. lol

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