Doubling the RAM to double the performance?
Doubling the RAM to double the performance?
On a personal computer with 512MB of RAM and installed with Microsoft Windows XP, a doubling of system memory lead to an increased performance as to be perceived as a significant increase in speed. This example, very deliberately crude, has been done to highlight some key points of this issue.
First of all we talked about responsiveness of the system perceived by the user, which is very difficult to quantify by numbers or by using benchmarks. However, it is an assessment that daily each user's own computer, while awaiting the launch of the operating system, while launching more programs or want to switch from one window to another. Since these operations depend largely on how much memory available, there is a dependency between the speed with which they are performed and the quantity of RAM.
In second place is worth noting that nothing you're saying about other characteristics of the computer. This simplification allows us to more easily expose the arguments, but it is good to note that any benefits data from the RAM are also influenced by other. Referring to the example always original, the perception of doubling the speed of the system would diminish all the more because the frequency of the processor (single core) was less than 2 GHz. This is because the benefits data dall'aumentare the amount of memory would be limited by the performance CPU.
Why is it possible to perceive this increased responsiveness of the computer in front of a doubling of RAM?
Basically, with more system memory available to happen less frequently having recourse to the use of SWAP. Every time you start a program, its code and data needed to it are loaded into memory, in whole or in part, and when not in RAM remains more room for more data is needed to remove part of those present. If applications are now completed then the memory can simply be reassigned and overwritten, if the data are still useful to a program running then can not be lost and shall then place it in a special area on the hard disk, the area of SWAP.
Imagine now that the data just transferred onto your hard drive are again requested by a running program, we again transferred into RAM and if it is not enough space there should be a further operation SWAP.
Since all operations SWAP involving the hard disk, they require much more time reading or writing in RAM.
With a larger quantity of memory so you can manage more data without having to resort to SWAP and the switch from a running program to another, or even from one window to another, in this case is extremely faster.
The limits in doubling of RAM
The limits in doubling of RAM
As we have seen so far, increase the amount of memory on a computer certainly brings benefits, although the effectiveness of the latter depends in part from the other components of your PC. However, it is not possible at will increase the quantity of RAM. On the one hand there is often a hardware limitation of the motherboard, which is related to the ability of each module of RAM installed, the other is the limit imposed by the features of the operating system used.
The 32-bit operating systems can use a maximum of 2 32 addresses, or can direct up to four gigabytes. It would therefore natural to deduce that you're able to manage an equivalent quantity of RAM, however, such addresses not only serve for the management of system memory but also for those devices that require MMIO (Memory Mapped Input-Output).
And 'as if, by simplifying, we had one hundred twenty labels but were confidential, then we could use up to eighty for our operations.
In particular, in the case of Windows operating systems, 4 GB of space available virtual address are evenly divided between applications and system. Therefore, in order to use more than two gigabytes of RAM is necessary to amend the parameter allocating these addresses, with a procedure known as RAM 4GT tuning. This makes it possible to reduce the addresses dedicated to the system and lead to a maximum of 3.3 those available for applications.
The 64-bit operating systems have available a greater number of addresses extremely well 2 64 corresponding to 16 terabytes, or more than sixteen thousand gigabytes. The amount of usable memory therefore varies according to the operating system installed.
Here is a summary table of the maximum memory installed Microsoft Windows XP and Vista.
As we can see from the table, all 64-bit systems allow you to reserve the necessary guidelines to the system, leaving much room for the use of four gigabytes of RAM.
For duty to chronicle also include the Physical Address Extension, which allows operating systems "professional" 32-bit to use more than 4 GB of system memory, as in the case of Windows Server 2008 Datacenter versions that and Enterprise has the limit 64 gigabytes.
