AMD Athlon 64 & Athlon 64 FX - It's Judgment Day
by Anand Lal Shimpi on September 23, 2003 1:25 PM EST- Posted in
- CPUs
Where does 64-bit help?
Although the performance that will sell the Athlon 64 today has nothing to do with this, the 64-bit part of the equation will definitely play a role in the processor's future. With no final release of the 64-bit version of Windows XP, there is no popular OS support (we will touch on Linux support as well as Win64 support shortly) and no real application support at this time, but where will the 64-bitness of the Athlon 64 help?
There are three main categories that you can split up the performance benefits into: 32-bit applications running on a 32-bit OS, 32-bit applications on a 64-bit OS and 64-bit applications on a 64-bit OS; we will be analyzing each one of these scenarios individually.
Case 1: 32-bit apps under a 32-bit OS
At the launch of the Athlon 64, the predominant operating environment will be running 32-bit applications under a 32-bit OS. All performance benefits the K8 architecture will show here are courtesy of the on-die memory controller, improved branch predictor, higher clock speed and more robust TLBs - none of the performance improvements you'll see in this case will have anything to do with the 64-bit capabilities of the processor.
Case 2: 32-bit apps under a 64-bit OS
When Windows XP 64-bit Edition is officially released (a public beta is due out at the time of publication), many users will be running their 32-bit applications under the 64-bit OS.
Outside of the performance improvements that we just outlined in Case 1, there are a couple of additional benefits the Athlon 64 may offer users. Currently under Windows, although you have a physical memory limit of 4GB, any given process can only use up to 2GB of memory; the remaining 2GB is reserved for use by the OS. With the 32-bit applications under a 64-bit OS scenario, each 32-bit application could be given a full 4GB of memory to work with, instead of being limited to the 2GB Windows process size limitation. Unfortunately this benefit isn't really "plug 'n play" as the application would have to be aware that it can use the added memory, which in the vast majority of cases would require a new patch to be made available.
The second benefit the Athlon 64 could offer in this scenario comes from the availability of additional registers. Although the 32-bit application would still only be compiled to use the regular set of 8 general purpose registers and standard set of FP and SSE2 registers, the 64-bit OS would be able to reference and use all of the registers at its disposal. The performance benefits that you would see here exist in any sort of task handling that the OS would be doing (switching between applications) as well as just regular Windows performance. Granted that the performance improvements seen here should be negligible, considering the extra overhead that does exist when running 32-bit applications in a 64-bit environment (more on this in a bit).
Case 3: 64-bit applications under a 64-bit OS
The final scenario is the one that shows the most promise, yet has the least amount of application support today - running a 64-bit app under a 64-bit OS. Here, the benefits are numerous; not only do you get the performance improvements courtesy of the Athlon 64's architecture, but each application now has full access to the increased number of registers and each application can use much more than 4GB of memory.
Although the Athlon 64 can support 64-bit memory addressability, for demand reasons it only supports 40-bit of physically addressable memory - or ~137GB, not exactly a limiting factor at this point.
The performance improvements developers are expecting to see under this final scenario has been estimated to be in the 10 - 20% range in tasks that are not memory bound, meaning those areas where the application is using less than 2 - 4GB of memory in the first place will still see sizable performance gains courtesy of the availability of more registers. We will investigate a few of these scenarios to substantiate (or refute) these claims later on in the article.
Performance improvements where you are memory bound will be even more impressive; just think about how slow swapping to disk is and how much faster keeping everything in memory makes your computer.
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Anonymous User - Thursday, September 25, 2003 - link
The Athlon64 FX doesn't have a multiplier lock either, but we never saw any results from that. Also I don't think a chip overclocking well means it's designed for "higher clock speeds".Anonymous User - Thursday, September 25, 2003 - link
toms just revised their review, "Update Sept 24,2003: Unfortunately we have made a mistake in the original article: In addition to the official P4 EE 3.2GHz we had included benchmark scores of the P4 Extreme 3.4GHz and 3.6GHz. These values were planned for a future THG article and were not intended to be included here. We would like to apologize especially to those readers who misinterpreted our charts. The two bars of the P4 Extreme 3.4GHz and 3.6GHz have now been removed. However, this issue does not affect our conclusion as we have only compared the official P4 3.2GHz EE to all other test candidates in our original article. For your information: The press sample of the P4 Extreme provided by Intel does not have a multiplier lock and is already designed for higher clock speeds. "Anonymous User - Thursday, September 25, 2003 - link
#81I also question why toms have a review to overclock P4 3.2 EE to 3.6 to win every performance chart. Is it fair to AMD? I like Intel CPU but I also like fair review.
Anonymous User - Thursday, September 25, 2003 - link
AMD needs to almost give this thing away so that it can sell well thus attracting a flood of 64 big developers. I think they should even do this to the detriment of their profit margins because if this doesnt sell well then all the software wont be developed. Its kinda like the chicken and the egg here and I think AMD should take a beating now in terms of $ to get this thing out and get 64 bit in the hands of the people. If everyone has it the software will follow.Anonymous User - Thursday, September 25, 2003 - link
Logic dictates that people whom use the term "fanboy" are mentally disturbed persons whom feel the need to categorize others into a certain group to make themselves feel better. On a side note though I think the Athlon64 3200+ is winner given its current availability, price, and performance. I’m just curious as to how far AMD hopes to scale the processor for the remainder of the year as though I already know there will be a 3400+ release in short time, I am wondering if there will be a 3600+ release in anticipation of Prescott. I’m also curious as to how quickly AMD will transition it to 90nm as I’m thinking one of the main reasons AMD hasn’t really made full effort in mass producing K8 processors are the manufacturing costs at 130nm. Either way it’s nice to see such a chip out, especially at the price it is being quoted for (though it seems some people are having fits that they can’t buy A64s for $100).Anonymous User - Thursday, September 25, 2003 - link
I think Intel is faring pretty well considering that AMD has reduced latency four fold with its integrated memory controller, incresed transistor performance by %30 with SOI, and doubled cache to 1MB. I think Intel will only close the gap with the upcomng Prescott but will pull ahead with LGA 775 Prescott and Grantsdale with PCI Express. Fanboys, save your speeches. Argue with logic.Anonymous User - Wednesday, September 24, 2003 - link
When is somebody going to come up with "folding" for people. We could use all the extra time people have on their hands debating what chip is better, to access their brain power to come up with cures for world hunger, A.I.D.S and introducing fanboys to fangirls. That being said, I appreciate all your opinions in helping me decide what chip to buy. Taking in to account the proccesing power I need for work and play, I have decided to buy an Xbox and a typewriter and forgo the 64 or P4EE.Anonymous User - Wednesday, September 24, 2003 - link
THIS FANBOY CRAP HAS TO STOP HOW NERDY CAN U BE??i am glad i am not so much into computers as most of u ;)...watch if one of these companies go out of business u see the survivor amd or intel making poor performing cpu's sold for $$$$ with a "take it of leave it" attitude...QUIT THE FANBOY CRAP truth is these companies don't give a shite about you only that little friend in your pocket that holds ur moneysprockkets - Wednesday, September 24, 2003 - link
The PM people believe that since they see the current situation in that Intel pays everyone not to use AMD, and that makes them a niche market. It's not due to AMD being slower or more error prone. Let's face it, Intel is bigger and has more to deal with, but as I've said before, they also can waste millions, perhaps a billion or so on Itanium and it's going nowhere. Perhaps it will now, but it's pretty stupid to see why. Sure it doesn't suffer from x86 legacy code. But look at what it took to get there, redoing software, apps, hardware, and a huge 400mm die. The Alpha people look to turn it into something, but that's alpha that made it something, otherwise it sucks.It's pretty stupid to argue here that the P4 3.2 ghz is faster or the emergency (good one :) ) edition is, the Xenon or even Itanium architecture with the cpus sharing a FSB and memory via a hub or northbridge architecture sucks compared to the hyper transport architecture the Opteron uses, and no amount of clock speed or memory speed is going to change that.
I wonder if Intel can now use it's own Itaniums instead of Alphas to run it's chip production line.
Anonymous User - Wednesday, September 24, 2003 - link
#91, That would be an expected outcome when half the tests are media/encoding benchmarks which are optimized for HT/SSE2. Not that there is anything wrong with that, just a simple note.