AMD 64 versus P4 32 bit processor

[Goi]

The best way to gauge which is "faster" and "better" would be to look at relevant benchmarks representing stuff you will do. If you play a lotta games, the A64 is clearly for you. If you do lotsa video encoding and/or video post-processing/resizing, the P4 still has a slight edge. In most cases though, a A64 would be faster than a similarly rated P4(eg. A64 3200+ vs. P4 3.2GHz).

The A64 and P4 Netburst architecture represent 2 different ideologies in micro-architecture. The former has a shorter pipeline, is clocked slower, but does more stuff per cycle by achieving a higher IPC(brainiac), while the P4 has a longer pipeline, is thus able to be clocked faster, but does less stuff per cycle, and suffers from penalties of a long pipeline(speed demon). intel bet the farm on this approach, but it turned out to be a mistake(power concerns and inability to ramp up production past 4GHz), which is why they will be concentrating on their more power efficient and higher IPC, lower clockspeed Pentium-M derivatives in the future.

 

[bim27142]

hhmmm... so 133Mhz FSB is the clock speed(just the clock as you've mentioned) and not the actual bus(FSB) bandwidth? did i get it right? then quad pumped to get the 533Mhz theoretically maximum speed of transfers?....

 

[EightySix Four]

Originally posted by: sbuckler

Originally posted by: Mik3y
the added benefit of the athlon 64 is the fact that it's 64-bit ready. it doesnt have any effect on how well it performs in the 32-bit environment. because of its architecture, hyperthreading, and on-die memory controller, the athlon 64 gets its performance from those and is clearly superior to the P4 overall.

In the above quote hyperthreading is a P4 feature not A64. Quite how important it is depends on what you do - if you like doing more then one thing at a time, particularly where one of those things is very cpu intensive (e.g. programmers often compile in the background while working on their code) then hyperthreading is essential. In the "dual core" future if all the apps go multi-threaded to be able to make use of both the cpus then that would mean single cpu's with hyperthreading would be able to run these apps much better. However I wouldn't expect many heavly threaded apps before 2006.

As to whether you need 64 bit it depends really on how cheap memory gets. The biggest advantage of 64 bit is you can have more then 3 or 4 gig of memory. You can take advantage of some additional 64 bit cpu instructions for more performance, but then there are disadvantages - you have doubled the size of all your pointers meaning a 64 bit program will need more memory and have to move it around faster to do the same thing as an identical 32 bit one. There will also undoubtedly be some backwards compatibility problems for early implementers (i.e. existing 32 bit apps/games not working properly).

Having said all that if you mainly plan to play games the A64 is undoubtedly quite a bit faster. I would buy one for a games machine but make sure you get a 939 one which has dual channel memory. Contrary to some opinions A64's do need the extra bandwidth sometimes, particularly with the newest games and when the going gets tough (e.g. in latest A64 4000 reviews the CS:Source test shows a 1.8ghz 3000+ with dual channel beating a 2.4ghz 3400+ single channel).

Actually the biggest advantage to the 64bit architecture is the extra registers used. There are more registers, which hold instructions, in 64bit mode, causing an increase in speed, in general testing, math intensive applications can benfit from 20-50% in speed increases. Also there will be some new things 64bit in the upcoming weeks, that may make 64bits worth it now, stay tuned and watch for new 64bit info, I don't think I'm at liberty to discuss them though, so just keep your eyes open, specifically in the gaming region

 

[AnnoyedGrunt]

Very nice discussion.

Just to throw my 2cents worth:
IMO, A64 and P4 @ equivalent ratings have essentially the same performance. While you may get slightly faster framerates in games, most likely you will be contrained primarily by the video card, and while the P4 may be slightly faster @ encoding, it's usually a couple seconds over a several minute encode.

Therefore, I think the areas of concern are things like upgradeability, power consumption, multitasking (hyper threading), etc.

My take is that currently Intel has better upgradeability (with the 775 mobos) and multitasking than the A64, but the A64 has much better power draw. Once NF4 arrives, I see upgradeability as a tie and really the biggest factors as power draw and multitasking. I personally prefer the 90nm A64's, but the Hyperthreading can be very nice as well, depending on what you do.

Plus, I like rooting for the underdog, which is currently another reason I like AMD. I'm impressed with what they have accomplished since the AXP.

EDIT: I forgot to mention the whole 64bit issue, which obviously is an advantage for AMD. However, I believe it is only a slight advantage, since the vast majority of people use the Windows operating system and since Win 64 still seems to be a ways off. I have a feeling that by the time Win 64 is ready for prime time, Intel will also have a 64bit chip available. However, I will remember that Intel was saying for a long time that 64bit wasn't needed on the desktop, and that MHz was critically important. Since they've backtracked on both those statements in the recent past, it is evident to me that AMD has been making much better guesses as to the direction of the market lately. Intel's P-M sure is a nice chip though. It'll be interesting to see what happens when they get that thing (or its derivatives) in a more mainstream platform.

-D'oh!

 

[jiffylube1024]

Originally posted by: Vee

But Bandwidth is a minor part of system performance from memory. More important is latency! That's why old systems with old sdram 133 do as well as they do, and why the new DDR2 standard fails so miserably, despite high theoretical bandwidths.

Hehe, yep, Intel loves their high bandwidth high latency chips. They bedded with Rambus, now they're doing it again with DDR2.

Originally posted by: Viditor
3. A64 uses a 64K L1 cache, P4 Prescott uses a 16K L1 cache

This isn't really a 'selling point' of either chips (their L1 cache) but just a product of their architectures, and the 64K of L1 cache is not what gives the Athlon64 it's kick nor it's high IPC, which is a result of the pipeline length. Plus, the massive full-speed L2 cache on both chips makes having a massive L1 cache unnecessary.

Also, I think the Athlon64 has 128K of L1 cache not 64K, just like the Athlon XP series (64K+64K).

Originally posted by: bim27142
:roll:
what are the pros of having a 64 bit CPU when there is no official 64 bit OS yet out in the market and most programs still are on the 32 bit world? not considering the future, if we take our reference TODAY, what's the real advantage of having 64 bit processor? does it necessarily perform faster over 32 bit?

bim27142 - the pros of having the Athlon64 today are, as stated above, because it's such a great 32-bit chip as well (the current performance champ, and a much superior gaming chip right now).

 

[Goi]

Originally posted by: Viditor

Originally posted by: bim27142
:roll:
what are the pros of having a 64 bit CPU when there is no official 64 bit OS yet out in the market and most programs still are on the 32 bit world? not considering the future, if we take our reference TODAY, what's the real advantage of having 64 bit processor? does it necessarily perform faster over 32 bit?

The advantage of the A64 TODAY has nothing to do with 64-bit...it's just a more efficient processor. The reasons for this are numerous.
1. On-die memory controller allows for much faster "turn-around" (latency) to the Ram
2. Shorter pipelines also alows for a "faster turn-around"
3. A64 uses a 64K L1 cache, P4 Prescott uses a 16K L1 cache

There are many other reasons, but they are quite complex. The P4 Prescott is still the champ at media encoding, though their lead has dwindled down to almost nothing lately.

You can't compare the L1 cache of the A64 with that of the P4. The P4 uses a trace cache rather than a conventional L1 instruction cache, which is quite a bit more accurate/efficient than a conventional instruction cache, hence the lower capacity. Besides, the purpose of the L1 cache is not to increase your hit rate, but rather to decrease your hit time, which is why they are often small, simple and fast. For example, the A64 has a 64KB 2-way associative L1 cache compared to a 512-1024KB 16-way associative L2 cache. It's not uncommon to see direct-mapped L1 caches.

 

[bim27142]

Originally posted by: bim27142
:roll:
what are the pros of having a 64 bit CPU when there is no official 64 bit OS yet out in the market and most programs still are on the 32 bit world? not considering the future, if we take our reference TODAY, what's the real advantage of having 64 bit processor? does it necessarily perform faster over 32 bit?

bim27142 - the pros of having the Athlon64 today are, as stated above, because it's such a great 32-bit chip as well (the current performance champ, and a much superior gaming chip right now).[/quote]
yeah, right!.. it's quite clear to me now why enthusiasts who really understand CPU architecture(and of course,know what their machine's are built for), tend to dig AMD chips over Intel...but to the more common people, Intel was just been there for quite some time now and their reputation lately to the masses is more of their "brand name" i guess...it's really great joining this forum and it was a very nice discussion indeed, no bragging, very professional...

damn now i wanted to sell my P4 system if only i could just afford another rig...

 

[badola]

hi,
IAm a programmer and want to buy the latest computer and i am curious to find out whether AMD will cause any problems when i compile my programs and run them.

P4 is widely used in SOFTWARE development but the same cannot be said about AMD.. so can i have any potential problem with AMD

 

[Markfw]

Originally posted by: badola
hi,
IAm a programmer and want to buy the latest computer and i am curious to find out whether AMD will cause any problems when i compile my programs and run them.

P4 is widely used in SOFTWARE development but the same cannot be said about AMD.. so can i have any potential problem with AMD

Yes the Athlon64's HAVE been widely used. And there are NO problems at all.

 

[uOpt]

Random remarks to other postings in this thread:

Registers don't hold instructions, they hold operands.

The trace cache on the P4 is not more space-efficient, but less so. It stores partly decoded instructions and those are bigger than the original in-memory instructions. So 12 KB of trace cache store less instructions than 12 KB of simple instruction cache. Of course, the advantage is that the transform from in-memory instructions to decoded instructions happens at an earlier stage. This construction is one of the major reasons why the P4 is so fast with code it likes and so slow with code it doesn't like.

I don't understand the remark "no official operting system". My employer and various other groups have plenty of AMD64 under Linux and FreeBSD in production use. For us Windows is the non-OS, we couldn't care less that it's not available.

If you are a programmer and know what you do in a machine-near language like C or C++ then you won't have problems. If you don't and produce bad code it will not like getting put on the 64 bit machine. If you use a higher-level language with a virtual machine or a tighter spec than C/C++ then you should have any problems, but depending on language some speed advantage might be lost. And obviously, not many virtual machine languages allow you to grow above 4 GB.

 

[0roo0roo]

a64 has cool and quiet

 

[uOpt]

Originally posted by: 0roo0roo
a64 has cool and quiet

According to my powermeter, AMDs with C&Q only achieved what Intel had anyway.

My 3400+ Newcastle consumes precisely the same amount as my Northwood 2.8C when idle (mainboards included).

My pre-C&Q AMDs were a lot worse.

 

[cbehnken]

Originally posted by: sbuckler

Originally posted by: Mik3y

In the above quote hyperthreading is a P4 feature not A64. Quite how important it is depends on what you do - if you like doing more then one thing at a time, particularly where one of those things is very cpu intensive (e.g. programmers often compile in the background while working on their code) then hyperthreading is essential.

Have you actually compiled ANYTHING on an Athlong 64? The code I compile (about 8 million lines for this one project) compiles MUCH faster on my A64 and I've no problems writing code while it compiles. I agree that hyperthreading does improve multitasking SOME, but I've had enough of people acting like you CAN"T multitask without it.

Windows XP is a pre-emptive multitasking operating system that actually multi-tasks very well (only 2.6 series Linux kernels can rival it).

To say you can't type code while something is compiling on an a64 is ludicrous.