Study Notes

EM64T, Intel Extended Memory 64bit Technology, is extension of 32bit system. This technology makes the OS support up to 16TB memory by adding bit-width for both CPU and memory, while 32bit only supports up to 4GB.

Today’s working is to estimate how much benifit we can get from application 64bit system if upgrade BA880 and all its components.

What does 64bit system mean to developers?By using 64bit platform, the developers can reach better performance when run their programs. Not only this way could encourage the developers to create more powerful applications, but also enable these applications more flexible to adapt in various environments. And the programers even do not need to upgrade their old knowledge if they want to develop in new 64bit platforms.

Larger memory accessing location and 64bit registers provide higher performance on 64bit system. Here, I compare 32bit system and 64bit. As we known, 32bit system’s limit is 4GB memory usage. If there’s a program which is required 3GB memory resource, then it seems the left 1GB(maximum) has to be allocated to OS. Obviously, OS will be slower. The networking server and database server would ofen encouter this problem. And at that time, this 3GB program must need some specical operating to internal code. For example, Physical Addressing Extension, PAE and Address Windowing Extension, AWE, enable 32bit application’s API to access 2GB or higher than 3GB memory space. However, these above special operation have to need more maintenance and resources, even some potential problems.

64bit platform can fix these problems very well. Less code can greatly improve the whole performance. The local bit OS also get benifit from added memory spaces. The all cache, buffer and handler become larger for general applications, and the system could be more stable and reliable. Larger cache and buffer can provide faster data accessing. and support more collateral users.

Register is the fastest memory style which OS can provide. The registers create and keep the results of CPU operating and other computings. 32bit x86 CPU normally has 8 registers, while 64bit x64 processor has 16 registers. There are 128 float-registers 120 general registers in Itanium platform.

As summary, when allocate more memory resource, the performance of register and system can reach higher level they would have never getten in former 32bit environment. 64bit LInux can support file as large as 4EB(2**63).