Monday, November 3, 2003		Feature

64-bit processor is ready. Are we?
O.P. Gupta & Kiran

APPLE has launched G5 system with a 64-bit processor. AMD has just released its Athlon 64 processor that has the support for the first 64-bit operating system (a variant of Linux). The 64-bit Itanium processor is Intel’s first product in the IA64 family of processors. It is designed to address the needs of high performance applications and incorporates many leading-edge features specifically designed to address the ever-expanding needs for highest floating-point performance and large memory capabilities.

Advantages

Bit rating of the processor determines the largest numerical number that processor can handle. The largest number that can be processed in a single clock cycle will be equivalent to 2 to the power of the bit rating. Thus, a 32-bit processor can handle a number up to 232 or roughly 4.3 billion. Any number greater than this will require more than one clock cycle to process. A 64-bit processor on the other hand can handle a number of a 264 or roughly 18.4 quintillion (18,400,000,000,000,000,000). This means a 64-bit processor would be able to more efficiently handle large number mathematics.

One of the other items directly affected by the bit rating of the processor is the amount of memory that the system can support and access. AMD supports 40 bits of memory registers rather than 64 bits and is able to support a total system memory of approximately 136 GB RAM. In addition, a 64-bit operating system can also allocate an individual 4 GB block of memory for each application. For high-end users that do CAD/CAM or scientific research, this can make a huge difference. It also is very important for server systems running large applications such as databases. The full use of a processor can only be taken if the software is written for it. Apple has started adding 64-bit patches for its operating system. AMD has taken a different route. It has designed its processor to handle the native x86 32-bit operating systems and then added additional 64-bit registers. This allows the processor to run 32-bit code as effectively as a 32-bit processor. The current 64-bit versions of Linux or the upcoming Windows XP 64 will utilise the full processing potential of the CPU.

Disadvantages

Running a 64-bit processor with a 32-bit operating system is going to end up wasting a large amount of the computing potential of processor. The 32-bit operating system is only going to use half the registers of the processor thus limiting its computing ability. It will still have all limitations on it that an existing 32-bit processor has with the same OS. Apple adds some additional support, but it is still running on a 32-bit OS. As far as memory support and accessibility goes this is well beyond what the memory market can even supply to computers currently. Now for most consumers, this won’t make much of a difference because most home systems don’t even come with 1GB of memory.

Is the timing right?

This requires a deep discussion. Most architecture changes such as 64-bit processors generally require a completely new set of programs to be written for them. This is a large problem for both hardware makers and software developers. Software companies don’t want to write new software until hardware is there to support software sales. Of course, hardware persons can’t sell their product unless there is software to support it. This is one of the major reasons why enterprise CPUs such as the IA-64 Itanium from Intel had problems. There was a little software written for the architecture and its 32-bit emulation to run the existing operating systems severely crippled the CPU.