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.: Technology Bytes : Mix Down Edition:
Bits, Bytes, Benchmarks & Beyond : Part 3 :

Januray 24 2004:

64-bit Computing: Ready Or Not – Here It Comes !

In Part 1 & 2 We covered the current CPU landscape with an overview of the latest and emerging technologies being offered by the 3 Major players, Intel, AMD, and Apple, and also the differences in the architectures of the competing CPU technologies, the apparent discrepancies in clock frequencies, and its relationship to overall Performance. This Month I’ll cover the emerging 64-bit landscape and its significance in the short and long term.

No doubt by now, you have probably been hearing about the advantages of 64-bit computing with both Apple and AMD trying to beat their respective drums as loudly as possible. Intel are playing their cards pretty close to their chest at the moment in regards to their X86-64 variant, but it is becoming more and more evident that they are also entering the playing field with 64 bit extensions on the next generation of Desktop CPU’s (Prescott) that are to be released next month. But is this current shift to 64-bit computing going to be a huge boon for the wider audience?

To try and understand the mechanics a little better, we do have to put on our propeller caps; I’ll try and explain this as straight forward as possible.

All computer processors are based on binary math because of the transistors that comprise the semiconductors inside the chips. To put things in very simple terms, a bit is a single 1 or 0 either stored or processed by a transistor. All processors are referred to by their bit processing ability. For approximately the last 10 years or so, 32-bit computing has been used since the introduction of Intel's 386 platform. So what does the bit count mean?

This 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. A 32-bit processor can handle a number up to 2^32 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 2^64 or roughly 18.4 quintillion (18,400,000,000,000,000,000). This means that a 64-bit processor would be able to more efficiently handle large number mathematics.

Are you still with me. ?? O.K, Spin it up again… :-)

One of the items directly affected by the bit rating of the processor is the amount of memory that the system can support and access. Currently 32-bit processors and operating system can support a total of 4 gigabytes of memory. Of the 4 gigabytes of memory, the operating systems can only allocate 2 gigabytes of memory to a given application. The 64-bit architecture however, can address about 18 million terabytes of information. In addition to this, a 64-bit operating system can also allocate an individual 4GB block of memory for each application.

Now for the vast majority of us, all of this won’t make a scratch of difference in our chosen real world applications, with 2 GB of Ram being more than ample for high end Audio / Video Applications. However, for some 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.

Fair enough, but a 64 bit capable CPU’s is only half of the equation. The other half is the Operating System and the actual Applications. 64-bit capability is only as good as the software written for it. Running a 64-bit processor with a 32-bit operating system is not going to be buying us any advantage. The 32-bit operating system is still only going to use half the registers of the processor, so it will still have all the same limitations on it that an existing 32-bit processor has with the same OS.

This is by no means a minor problem. Most major architecture changes such as 64-bit processors require a completely new set of programs be written for them. This is a major headache for both the hardware makers and the software makers. The software companies don't want to write the new software until the hardware is out there to support their software sales. Of course, the hardware companies can't sell their product unless there is software to support it. A classic case of Catch 22.

This is one of the major reasons why enterprise CPUs such as the IA-64 Itanium has not gained the acceptance that Intel had hoped. Even though Microsoft have supplied a dedicated 64 bit version for the IA-64 code, there is little software written for the architecture and its 32-bit emulation to run the existing operating systems and applications severely cripple the CPU.


 

So, how are the major players getting around this problem? Apple has started adding 64-bit patches to its OSX operating system to allow it to access more than 4 Gb of physical RAM. ( the G5 can support upto 8 Gb ).The latest revision Panther has added some additional support ?, but it is still only a 32-bit OS. A true 64 bit Mac OS could still be years away. AMD is treading water waiting for Microsoft to release Win XP-64 /2003 – 64 which will have the required 64 bit extensions to enable their X86-64 line of CPU’s to utilize the full processing potential. Although already in Beta, the release has now been shifted back to Q3 –2004.The delay in releasing the OS is a concern for AMD ‘s marketing strategies, and has also opened another huge can of worms for the conspiracy theorists to explore.

It is rumoured that the delay is due to the fact that Microsoft is waiting for Intel to officially announce its own variant of X86-64 (Yamhill). It now seems likely, despite AMD banging the drum rather loudly to the contrary, that Microsoft has no plans whatever to release an OS that will run only on AMD 64-bit CPUs. Its obvious now, that Microsoft thought it would be far wiser to hold off the release of Windows XP/2003 for X86-64 until Intel declares its intent to also provide a similar technology on its future chips. That way if you have an X86-64 code base and processor architecture specific extensions for both AMD and Intel, the install routine could detect which host processor is in play, and then will install the correct elements of Windows. Seems pretty sensible to me.

Unfortunately for AMD the delay has had the effect of freezing its fragile momentum as prospective customers wait and see exactly what Intel have up their sleeves. To add further to their woe, if Intel’s 64 bit extensions are incompatible to AMD’s, it could definitely spell disaster as software developers would then have to compile for both variants, and would most likely code for the Intel variant first, due to its majority market share. Ouch !!!
Now all of the above means diddlysquat without the applications to take advantage of the extended 64 bit registers. That could take quite a while yet. Porting or re writing applications to 64 bit is no minor feat, to say the least, and as mentioned before Software companies will be waiting for the 64 bit hardware market to expand to a point for them to make it a viable proposition to recode their software arsenals.

Now despite both AMD and Apple presenting 64-bit computing as a major performance advantage with immediate wide reaching relevance, it is not entirely the case. True, the ability of these 64-bit platforms to support large amounts of RAM can speed up memory-hungry programs, and the larger register sets associated with 64-bit CPUs can improve performance on recompiled 32-bit applications, but these are not very dramatic effects. Interestingly, most performance benefits related to 64-bit processing have already been realized in 32-bit systems by means of instruction-set extensions such as Intel's SSE, AMD's 3DNow!, IBM/Motorola's AltiVec, All these extensions implement 64-bit (or wider) data paths and register sets for special-purpose instructions. That’s not to say that a true 64-bit data path will not offer some improvement, but it will not be as dramatic as some would have us believe.

So what’s it all mean? Both AMD and Apple have a very strong vested interest in making the argument for 64 bit processing in their marketing efforts, but in reality their improved performance has nothing to do with 64-bit capabilities. All the “ hyperbole “ is little more than an attempt at muddying the waters enough to try and gain a few points in regards to marketing. Despite any matter of truth, this “ argument “ will still be the centerpiece of the Athlon 64 and G5 marketing efforts, as both companies continue trying to sell their 64-bit story, however weak it is.

No doubt 64 bit computing is going to be a dominant factor in the future, but it may still be quite a few years before the shift is complete, so for the immediate future, although 64 bit hardware is available now for the Desktop/Workstation environment, the true benefits are still quite a while away. That’s not to say that the current offerings from AMD, Apple, and the forthcoming Intel Prescott are not viable, modern day powerhouses. They are however 64-bit systems living in a 32-bit world, and should be considered for their performance with current 32 bit Apps, not for some 64-bit promised land which is, realistically, still years away.

Till next time :-)

Part I

Part II

© TECHNOLOGY BYTES 2005

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