You need to sort a file of n Gigabytes stored on a hard-drive. Your RAM contains

Question

You need to sort a file of n Gigabytes stored on a hard-drive. Your RAM contains only 5GB. You have a lighting-fast CPU, but writing or reading from the disk (a single I/O operation) is slow. So we estimate the number of I/O, and ignore CPU time. For simplicity, assume your disk is partition into blocks, each of size 1GB. In each I/O operation, you could read or write one block. The input file occupied the blocks b1 . . . bn. Explain how to sort the file, using O(n log n) I/O operations. You could assume that your hard-drive contains n blocks of free space f1, f2 . . . , fn. Ignore caching issues. After the sorting is executed, the smallest key of the file is at b1, the largest at block bn, every keys of block bi is smaller than every key at block bi+1 etc

Explanation / Answer

Shared Video Memory: Using part of main memory (RAM) for the display circuit's frame buffers, which temporarily hold the rendered content being sent to the screen. Shared memory is used in PCs that have the display circuit built into the motherboard rather than housed on a separate, more costly display adapter card.

Sharing main memory with the display function reduces the amount of memory available to applications, and main memory is not as fast as the specialized video memory on stand-alone cards.

On lower end systems, the video is integrated into the motherboard. The video controller uses a certain amount of 'shared RAM' for video memory. The shared ram is taken away from main system RAM. Thus, on a 512 Mb system, if the integrated controller uses '128 Mb shared video RAM', the main system only uses 384 Mb of RAM, and this is the number you'll see when checking for the memory.

When you go out to purchase a computer, some models specify that they have a certain amount of megabytes of memory, and they may have a video card that supports a certain amount of shared memory. This means that when the video card is in use, especially in higher display modes, it will take some of the memory normally dedicated to other computing activities and use it as its own. Thus, if you buy a computer with 512 Mb of memory and 128 Mb of shared memory and you frequently use a high display settings, you may actually only have 384 Mb of physical memory available left to your computer. In some advance systems, the use of Shared video memory can be changed dynamically while the system is running, that is, at one time it may be using only 64 Mb of memory out of 128 Mb shared and dynamically change it as the demand increases or decreases. While this may be fine for some people, if you have more money, you may want to go with a computer that has video memory dedicated to the video card, saving your physical memory for other uses. A computer with 512 Mb that uses 128 Mb of shared video memory will have a gorgeous display but run poorly because Windows Vista only has 384 Mb to use (minimum recommended memory for vista is 512 Mb and 128 Mb of Video memory).

Dedicated memory means that the video card uses its own memory, and doesn't share or take up the memory from your RAM. Other than that the dedicated video card would be good for graphic intense application (CAD) and video editing, games and will also help in running windows vista ( with Aero - the new Vista user interface) smoothly.

The Advantage of a video chip with shared memory is that it is cheaper, it won't be horrible, but it won't play games (lack of RAM, and I wouldn't suggest it, this excludes flash games), and video editing won't be great (but that may not apply to ripping).

I would never buy a machine with shared video memory because 20% performance loss is not worth the small price savings realized.

As far you?re requirement goes you don?t require a high level graphics card, as you said, you?ll be doing some casual gaming I?ll suggest get a lower to mid-range video card. Make sure you buy a card that matches your expansion slot type. 256MB of dedicated memory should be enough for you. You can find cards ranging from 128MB to 2GB of memory, depending on how much you want to spend. Nvidia GeForce 8400 GS/8500 GT or ATI Radeon HD 2600 Pro are my preference for a mid-range budget. Make sure the card has a HDMI, Display Port, or a DVI output. This would also help you future proof your system.

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