Friday, June 17, 2005

So what is 64-bit?

It's the 64-bit question ...

Chris Green explains what the technology has to offer PC users - today and in the future.

Chris Green, Computing 15 Mar 2004

64-bit is the next generation of PC processor technology. Unless the PC on your desk is pre-Windows 95 (unlikely), it has a 32-bit processor. If it's very new, that chip will be a Pentium 4 or an Athlon XP.

64-bit chips are the next stage, delivering even more processing power and new technologies to improve graphics performance and web surfing.

How did we get to 64-bit?
The original x86 processor had eight-bit internal data pathways, so it could process eight bits (or instructions) at a time. The next development, the 386, was called a 16-bit processor because its internal data pathways were 16-bit, and so on.

The past 26 years have seen us move gradually through various developments in PC technology. The PC as we know it was born in 1978 when Intel released the 8086, an eight-bit processor that was used in the original IBM PC.

Intel went 16-bit in 1985 with the 386 and 32-bit in 1989 with the 486-DX. The original Pentium was also 32-bit.

The next evolution is 64-bit, which is capable of handling twice as many instructions again at a time, and capable of transporting those instructions through the pathways at a phenomenal rate.

OK. But processor technology gets faster all the time. So what?
This is a bit more significant than the usual round of slightly faster chips. 64-bit represents a move to a completely new hardware technology, one that eliminates many of the performance bottlenecks of current 32-bit technology.

The evolution from eight-bit to 16-bit, and particularly from 16-bit to 32-bit, saw the newer incarnations of the chips being saddled with a lot of legacy baggage to ensure compatibility with legacy software.

The move from the current 32-bit chips to 64-bit will deliver a major leap in performance, because legacy support is either being dropped completely or is ring-fenced within the processor.

This means that the 64-bit capability is not hampered by slower, more inefficient 32-bit instruction sets and data handling. Instead, 64-bit chips are free to use new hardware technology that can be exploited by future software and operating systems.

You said future?
As is always the case with these things, the hardware is out before the software that will take advantage of it. But software is playing catch-up. Microsoft is planning to release a 64-bit version of Windows XP this summer.

There are also several builds of 64-bit Linux in the offing, including a version from Mandrake that is optimised for AMD's 64-bit platforms.

And I suppose I'll need to replace most of the guts of a machine if I upgrade it?
The 64-bit chips have different pin arrangements and power requirements than even the latest Athlon XP and Pentium 4 processors, and they rely on completely new motherboard chipsets.

So in short, if you are looking to upgrade a machine in situ, you'll need a new processor and a new motherboard at the very minimum. You'll almost certainly need some new memory as well.

Who's making these chips?
The usual suspects: AMD and Intel. Interestingly, AMD is very much running the show this time round. It has beaten Intel to market with a 64-bit desktop processor by six months. Intel didn't even announce plans to add 64-bit extensions to existing 32-bit chips until February this year.

But wasn't there already a 64-bit Alpha processor?
Yes, the Alpha server and workstation processor developed by DEC was indeed 64-bit. Sadly, when DEC was acquired by Compaq, development of the Alpha was quietly dropped, and the technology has begun to fade from active use and support. For example, Microsoft dropped OS support for it after NT4.

However, the Alpha continues to have a role to play in 64-bit computing. AMD licensed part of the Alpha bus technology for use in the Athlon XP, and hired many members of the Alpha development team.

This knowledge has carried forward into AMD's Athlon64 and Opteron, while Intel eventually acquired the technology from Compaq in late 2001.

So which 64-bit chips are available now?
AMD has two 64-bit processors: Athlon64 for desktop PCs and laptops, and Opteron for servers.

Both of these are fully backwards-compatible with existing 32-bit software and peripherals. Intel's 64-bit server platform Itanium, however, is not backwards-compatible, although its 64-bit extended chips will be.

So even though there is no 64-bit software out there, can I still use a 64-bit PC?
Yes. You can buy 64-bit hardware now, and use your existing software on it. 64-bit PCs will even run 32-bit software with a decent performance gain.

As and when 64-bit operating systems and applications come on the market, you will already have the infrastructure in place to run them.

OK, so how much is a 64-bit PC going to cost me?
Not as much as you might think. Retailers such as PC World are selling high-spec AMD-based 64-bit PCs in the £1,000-1,500 price range, and IBM is shipping Opteron-based servers starting at £2,000 for a single-processor machine. HP and Sun are also due to launch Opteron products this year.

In the light of recent comments by Michael Dell, there is even a possibility that Dell might break with its traditional Intel-only stance and release a range of AMD 64-bit based servers.

As for Intel, Itanium 2 processors are almost exclusively used in supercomputer applications at the moment, making it difficult to put an everyday price on them. However, 64-bit extended desktop processors should start appearing in the second half of this year.


Missing from this picture is Cyrix, a little-known brand that was once independent, has since been owned by National Semiconductor, and now belongs to chipset maker VIA.

Like AMD, Cyrix produced x86-compatible processors under licence from Intel during the years of the 80286 and 80386. Cyrix then decided to make its own processors and created the Cyrix 486.

Again like AMD, it continued to produce its self-engineered x86 compatible processors, but ran behind Intel in terms of getting comparable products to market at the same time.

In 1997, Cyrix released its most successful x86 clone, the 6x86MX - a rival to Intel's Pentium MMX. Cyrix licensed the MMX extensions from Intel for use in the chip. This, along with AMD's K6 and later the K6-2 processors, competed with Intel at the lower end of the market.

In 1999, Cyrix was sold to VIA and has since conceded the mainstream market to AMD and Intel. Instead, Cyrix is focusing on so-called 'computer on a chip' 32-bit products.

The Cyrix MediaGX processor, for example, is used extensively in set-top boxes and embedded devices. VIA also uses Cyrix processor technology in complete chipsets for ultra-small ITX PC motherboards, which are popular with computer gamers, Linux users and individuals looking for very small, low-noise and low-power x86-compatible PCs.



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