Anyway, there is one more aspect to this question: the memory access. The thing is that in the basic “flat addressing” mode the same general purpose registers are used to store memory access addresses. 32 bits allow saving 4.3 billion of possible combinations, so that the 32bit processor can cope with only 4.3GB of memory. Its registers simply cannot store the addresses of those cells, which exceed the above mentioned limit.

Of course, the advantages of 64bit technology are evident here, because the size of the addressed space grows up to 18 million terabytes. Even though 4GB of memory can still be seen only in servers, we anticipate that very soon this memory capacity will become a common thing for PCs as well. As we have just pointed out, 64bit technology will ensure a theoretical capacity of 18 million terabytes. The practical value will definitely be lower than that, but it will still be enough to last a few tens of years.

So, since we came to speak about servers, it seems the right time to ask: what are the advantages of the 64bit technology? Who will benefit from that? Of course, the first thing that comes to our mind is the notorious database servers. Serious databases have already exceeded 4GB in size, and the opportunity to cache them completely in the RAM is too attractive to give it up. So, just like incase of coprocessor, the server solutions makers didn’t want to wait for someone to solve this problem. Thanks to different tricks they managed to make 32bit Xeon capable of addressing over 4GB of data (up to 64GB). Although you should keep in mind that these hacker-like solutions can hardly be called a serious platform for the future, and besides, they cause a too big performance drop when working with the memory: it can be measured in tens of percents. Anyway, the future from Intel is connected with the Itanium processor and not with Xeon.

Well, this is about it. It is pretty hard to think even of a workstation that might need more than 4GB of memory. We don’t doubt that the 2D and 3D applications as well as video processing tasks will be improved so greatly within the next few years that we will easily overcome this undeclared barrier. Nevertheless, today 64bit technology is hardly of any real practical value.

It is simply ridiculous to talk about Word, games and the like, although on the other hand, we can imagine that more memory could be needed for some games displaying highly realistic worlds with high level of detail. Just think of all servers supporting Ultima Online or Everquest being a prototype of a mainstream gaming PC of the future.

However, some of you may have already noticed that the whole discussion is based on the 64bit addressing, as if it were the only advantage of 64bit processors. Does it mean that nothing is going to change for integers when we start using 64bit representation? Of course, it is not quite true. Something will definitely change, but mostly for the already mentioned servers in the first place, which deal with such tasks as simulations of nuclear explosions and weather, cryptography, and the like, where 32bit integer range may be not enough. As for the common PCs, 64bit will find no real application. By the way, if you really need 64bit representation so badly, such high-end programming languages as C, for instance, allow using standard focus, when two 32bit registers are used for a 64bit number. Which will definitely affect the performance a little, because the number of available registers is strictly limited.