# I need a new cpu.. amd64 or p4?

## Maranza

i need to buy a cpu+mobo+memory replacement for my pc..

i was interested in the p4 3.0 GHz "prescott" since it's relatively cheap by now and delivers decent computing power (i've got an athlon xp 2000+, it would be a significant leap forward, 1.6GHz to 3GHz, 333MHz fsb to 800MHz). It is a common opinion that, since a true 64 bit windows os with common 64 bit apps won't be available for at least a couple of years, a p4 would be a better choice (cheaper, at least) than the athlon64 for the standard windows user. But wait a minute! Am i a gentoo user or what? Can't i compile EVERY app with native 64-bit support? Indeed i do. I read a few docs, and even if there are a few problems still pending (openoffice, java ecc) the choice is "practically" safe. Now, i'm sure that a new AthlonFX 64 "motherfucka" which costs 999$ would be faster than a P4 3GHz, my question is whether an amd64 configuration with the same budget as a p4 would be convenient.. or is 64-bit still a dream for the budget-less (meant as infinite  :Wink: ) geeks?

Using a 64-bit processor on a 32-bit environment isn't worth the bucks.. what about using it in a 64-bit one? Keep in mind that i run my gentoo desktop mainly for surfing the internet, listening to music, playing a few games and developing in c++/python, so no fancy video-editing or 3d-modeling..

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## fennec

I had same chip than you and got my self a prescott because :

1. HyperThreading looked attracting

2. 1 Mb cache

3. Chipsets aren't only via and sis

For now i am satisfied with the performance.. but note that i bought 2 sticks of 512 ddr for dual channel and a Western Digital raptor hdd ( 10k rpm )

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## Lucho[FLCL]

Keep in mind that Dual channel memory is only available on 3500+ or upper or FX series for the AMD 64's. The lower clock-rate'd 64's (and cheaper) only have single channel memory support (this is because of different cpu cores).

The prices are different too...single channel memory controller 64's are wayyy cheaper

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## Maranza

so you think getting a single channel athlon 64 isn't worth it? I think i'll have to buy another cpu+mobo+memory next year because i've got two pcs... i'll wait for the 64bit to get cheaper and then "thrash" the prescott into my brother's pc  :Smile: 

would you do the same?

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## daemonflower

 *Maranza wrote:*   

> Keep in mind that i run my gentoo desktop mainly for surfing the internet, listening to music, playing a few games and developing in c++/python, so no fancy video-editing or 3d-modeling..

 This sounds as if you should be quite content with the cheapest solution available, whichever it is... 

From my point of view, AMD64 was well worth the 100 or so extra bucks I invested in it. The only feature which I consider in favor of P4s is hyper-threading. For me, doing a lot of heavy, memory-bound calculations, this is not much use. If you do a lot of interactive stuff, it may well be better suited.

In my opinion, a lower-end AMD64, such as 3000+ or 3200+, gives the best performance for the buck. I don't have any benchmarks at hand to prove my opinion, though. Just my 2 cents.

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## Redeeman

get amd64, p4 sucks

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## Travers

It depends on what you want to do. If you are doing media editing/publishing... go for the p4. (Oh, and don't do hyper-threading, since it is generally slower. I'm not sure if support for it has to be in the source or if you can compile it in...) If photoshop is your thing or you are doing movie editing with Pinnacle, go P4. 

The AMD64 will be far superior with number cruncing and compiling. Don't do 64 bit since there are some closed-source drivers and programs... like the flash plugin. Open Office won't compile eiether. You get the idea.

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## daemonflower

I have to disagree with much of what you said. I've benchmarked hyperthreading and with apps with small memory needs I found a 10-20% speed increase, especially if you run different apps at the same time. Like I said earlier, this advantage goes away if you need to access lots of RAM, because the two virtual processors share one bus. With about 50 MB of RAM (which have to be accessed all the time, as in number crunching; this argument is less valid when the RAM is only accessed sporadically, as in most interactive applications) the advantage of hyperthreading vanishes, and with very large data sets (beginning with ~500 MB) hyperthreading was indeed slower than no hyperthreading.

This is based on my own benchmarks, which were sort of special cases, mind you. The other advantage of HT, which is that you get a snappy user interface, while some process is chugging away happily in the background, is more based on my feeling for responsiveness, than hard benchmarks. 

About the 64 bit system, I definitely recommend it. It is way faster (no benchmarks here to suppurt this, I'm afraid) and the compatibility issues can be solved by the emul-linux-x86-* libs and in the worst cases, a 32 bit chroot. In other cases, 32 bit binary packages solve the issue. I run firefox-bin with flash plugin on my AMD64 with no problems.

About OOo (Eclipse is another package which cannot be compiled, apparently)... what's wrong with using binary packages once in a while? OOo and Eclipse run fine here as binaries.

That said, I agree with your assessment of the usage of P4 and AMD64. Media for P4, "serious work" for AMD.   :Wink: 

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## daemonflower

Oh, I forgot one thing about the compatibility issue:

DON'T use ATI graphics cards with AMD64. There are indeed no drivers for them yet, and nobody but the most hardcore optimists expects them any time soon.

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## GentooBox

I have a AMD64 3000+ with Geforce 4 TI4200.

I can play any game i want because the nvidia drivers can use 32 bit or 64bt mode.

you can even start your computer with a pure 64bit system and play a 32bit game in full-speed.

AMD64 cpu's are faster than ever, its insanely fast !

The AMD64 cpu IS faster than a Pentium4 on the same price level.

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## mirko_3

 *daemonflower wrote:*   

> Oh, I forgot one thing about the compatibility issue:
> 
> DON'T use ATI graphics cards with AMD64. There are indeed no drivers for them yet, and nobody but the most hardcore optimists expects them any time soon.

 

Ati drivers for 64-bit are coming out in December, and with xorg 6.8 support as well... ATI said so!!  :Very Happy: 

No, really, they said so, so they should come out.. whether they're good, we'll see... they're also supposed to be based on the windows codebase..

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## Travers

Oh, and about that dual channel memory controller, it dosen't give you any performance increase because the dual channel is only on the Newcastle core that has only 512K L2 cache. The Clawhammer core, without the dual channel, has 1024K of L2 cache. They perform just about the same. The introduction of dual chanel will give about a 5% increase in performance, but you loose that benefit since you have half the cache.

It's cheaper for AMD to put in half the cache and a dual channel controller. Besides, socket 754 is their unwanted child despite it being a perfectly ok platform...

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## Lucho[FLCL]

 *Travers wrote:*   

> Oh, and about that dual channel memory controller, it dosen't give you any performance increase because the dual channel is only on the Newcastle core that has only 512K L2 cache. The Clawhammer core, without the dual channel, has 1024K of L2 cache. They perform just about the same. The introduction of dual chanel will give about a 5% increase in performance, but you loose that benefit since you have half the cache.
> 
> It's cheaper for AMD to put in half the cache and a dual channel controller. Besides, socket 754 is their unwanted child despite it being a perfectly ok platform...

 

In modern PC's, the CPU is idle while waiting for memory a lot of time (this is only helped by the cache memory inside the CPU, who has in turn to read from the memory....who has in turn to read from the disk), so a higher memory bandwith means higher CPU utilization in most of the cases...it's true that a bigger cache should cope for this in some way, but it's application-dependant and cache-hit-ratio dependant.

If you have a lot of applications running at the same time, a higher memory bandwith should be better, since cache misses are more likely to happen.

This is not something easy to discuss...., I'd go for a p4 and it's dual-channel memory PLUS 1MB cache.  IF you want to keep your PC unchanged for more that 2 years, it's probably better to go AMD 64, despite memory speed limitations.

IF you have a lot of money, go for a 3500+ or higher AMD64, dual channelled. It must be VERY fast....  :Crying or Very sad: 

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## Travers

L2 Cache  is important. Intel is starting to realize this and we will be seeing the Dothan (Pentium M) not the Prescott (P4, Xeon) starting to take the lead in the mainstream desktop market. The Prescott core just plain sucks, no other core performs so poorly per clock cycle. That's all Prescott was about -- clock cycles, not actual performance. Dumb end-users though that clock speed was the standard for measuring performance and quality. HAH! But, anyhow, Pentium M is going to be big in desktops Q2 2005. Why? Because it has 2MB of L2 cache! Intel also plans to add another MB for a total of 2MB L2 to their Prescotts by Q2 of 2005. Literally half the freaking core of transistors will be devoted to the cache for both processors. 

I agree, it is not a good thing when your processor is waiting for data from the RAM. It will idle and you will loose performance since a few milliseconds are a long time for computer. But that is what the integrated memory controller in the 64 series is for. The memory controller is built into the processor and communicates DIRECTLY WITH THE RAM! All Intel chips have to go through the northbridge to get to the ram and go through it again to get back. 

AMD is A to C

Intel is A to B to C

You do the math. 

But about that dual channel compared to the 1MB of L2 cache. You will have the same performance eiether way. This is only 5% of the processing power we're talking about. The two are interchangible. It's just cheaper for AMD to do half the cache and dual channel than it is to do 1MB of cache and no dual channel. I personally would do 1MB of L2 just since you don't have to worry about incompatible ram.

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