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Topic Title: Guide to Athlon 64/Athlon 64 FX platforms
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Created On: 08/23/2004 12:03 PM
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 08/23/2004 12:03 PM
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Current and upcoming platforms for the Athlon 64/Athlon 64 FX Processor
– An architectural overview

In the relatively short time between now and the Athlon 64/Athlon 64 FX Processors' introduction in September 2003, a host of different platforms has emerged on the market.
Different Sockets, different chipsets – each with their own specific properties and features – but which one suits YOUR personal needs best?

This article will give you a brief overview about the Athlon 64/Athlon 64 FX's basic architecture that all platforms have in common.
After the basics have been covered, we will deal with the Sockets and finally we will have a look at all the different chipsets currently on the market as well as upcoming chipsets that are going to be released in the immediate future(i.e. until the end of 2004).

Part I: Basic Architecture

The basic architecture of ALL Athlon 64/Athlon 64 FX platforms differs significantly from that of any 'classical' platform(e.g. Athlon XP/Pentium 4).

First of all, the Athlon 64 has an on-die memory-controller which means the memory-controller is integrated directly into the CPU-core instead of being part of the chipsets' Northbridge.
This significantly reduces latencies when accessing memory as the memory has its own dedicated path directly connected to the processor – memory-accesses no longer have to go through an FSB(Frontside Bus, aka System Bus) like on a 'classical' platform.

Furthermore, an Athlon 64 does not even have an FSB in the 'classical' sense anymore.
The processor communicates with the chipset and thus the 'rest of the system'(excluding memory, of course! via a Hypertransport-link.
Unlike the rather slow parallel architecture of a 'classical' FSB, Hypertransport is a fast, scalable serial point-to-point interconnect.

You can find more info about Hypertransport here' ">

Athlon 64 processors also feature Cool'n'Quiet as well as enhanced virus protection(EVP).
Cool'n'Quiet is a powersaving feature that will dynamically adjust the processors' clockspeed and voltage depending on CPU-utilization/load.
The Athlon 64's enhanced virus protection(EVP) feature helps to protect your system from many viruses and trojans in conjunction with Microsofts' Service Pack 2 for Windows XP.

Part II: The Sockets

Currently, Athlon 64/Athlon 64 FX processors are available for three different Sockets: Socket 754, 939 and 940.
Now what's the difference between these sockets?

Socket 940
Socket 940 plays only a minor role for Athlon 64 FX processors at this point – it is a Server/Workstation platform designed for AMDs Opteron processors.

The first Athlon 64 FX, the FX-51, as well as it's immediate successor, the FX-53 were released on Socket 940 to distinguish AMDs fastest enthusiast desktop processors from the 'normal' Athlon 64's(which were Socket 754 only at that time).

Socket 940 processors have a 128-bit, 'dual-channel' memory-controller and require registered memory – they DO NOT support Cool'n'Quiet.
All current Socket 940 processors have 1MB of L2-cache.

The Athlon 64 FX-51 and FX-53 are the ONLY non-Opteron processors for Socket 940 – ALL future Athlon 64 FX processors will be released for Socket 939(the FX-53 is already available in a Socket 939 version).

Socket 939
Socket 939 is AMDs latest Socket for both Athlon 64 and Athlon 64 FX processors.

Socket 939 processors also have a 128-bit, 'dual-channel' memory-controller, BUT unlike Socket 940 parts they use unbuffered(non-registered) memory which is slightly faster and less expensive than registered memory – ALL Socket 939 processors support Cool'n'Quiet.
Current Socket 939 Athlon 64s('Newcastle', model F) have 512KB of L2-cache while Socket 939 Athlon 64 FX processors('Clawhammer', model 7) have 1MB of L2-cache.

Socket 754
Unlike Socket 939/940 parts, Socket 754 processors only have a 64-bit, 'single-channel' memory-controller and use unbuffered(non-registered) memory – ALL Socket 754 desktop processors support Cool'n'Quiet, mobile parts support PowerNOW!.

Socket 754 belongs to the Athlon 64 and Sempron(Socket 754 version) processors as well as their respective mobile counterparts – there are NO Athlon 64 FX processors for Socket 754.
Current Socket 754 processors have either 1MB, 512KB or 256/128KB(Sempron) of L2-cache.

Part III: Chipsets

The first Athlon 64 motherboards(Socket 754) available on the market were based on VIA's K8T800 chipset – it is a solid performer which supports AGP 8x and the full bandwidth of the Athlon 64's 800MHz(1600MHz effectively) Hypertransport link – the K8T800 uses the VT8237-Southbridge which features on-chip S-ATA RAID, 6- or 8-channel audio(depending on external chip/codec) and eight USB 2.0 ports.
The K8T800 chipset is used on Socket 754 and a few Socket 940 motherboards.

With the introduction of the new Socket 939 processors, VIA launched their K8T800Pro chipset, a slightly improved version of the original K8T800 with added support for the Socket 939 processors' faster 1000MHz(2000MHz effectively) Hypertransport-link as well as a faster connection between the chipsets' North- and Southbridge('Ultra-Vlink' at 1066MB/s vs. '8x-Vlink' at 533MB/s on the plain K8T800 non-Pro).
Unlike the plain K8T800(non-Pro), the K8T800Pro supports fixed AGP/PCI-clocks which facilitates overclocking.
The K8T800Pro chipset also uses the VT8237 Southbridge(so it has the same features in the sound, S-ATA, USB, etc. department) and is currently available on both Socket 754 and Socket 939 motherboards.

VIA also offers an Athlon 64-chipset with integrated graphics – the K8M800.
Basically, it is a K8T800(non-Pro) with an integrated VIA Unichrome Pro GPU(shared memory).

Later this year, probably in early Q4, VIA is going to launch their new K8T890 chipset.
It will be a PCI-Express enabled chipset featuring a PCI-E 16x slot(for videocards), one PCI-E 4x slot(could be used as four PCI-E 1x slots) as well as AGP 8x and of course the 1000MHz(2000MHz effectively) Hypertransport-link, fixed PCI/AGP clocks and Ultra-Vlink.
Furthermore, the K8T890 chipset will use the new VT8251-southbridge which will support two additional PCI-E 1x slots, four S-ATA/RAID channels(AHCI with Native Command Queuing support), Gigabit-Ethernet and 'Azalia'-compliant 8-channel audio.

More info about VIA-chipsets here' ">

Specification and feature-wise, Nvidia's first Athlon 64 chipset, the Nforce3 150, doesn't stand up too well against VIA's K8T800: It does support AGP 8x, but it can only run the processors' HT-link at 600MHz(1200MHz effectively) instead of the full 800MHz and it also has only half the in the upstream direction(chipset-to-processor, upstream link is only 8-bits wide instead of the standard 16-bits).
Furthermore, the Nforce3 150 does NOT have on-chip S-ATA and features only six USB 2.0 ports.
To be fair, the Nforce3 150's slower HT-link does NOT noticably affect performance in the real world – even the Nforce's comparably low bandwidth of 3.6GB/s(vs. 6.4GB/s for the K8T800) is more than enough for any modern motherboard.

The Nforce3 150's successor, the Nforce3 250/Gb is a totally different story – like the K8T800Pro it supports a 1000MHz(2000MHz effectively) Hypertransport-link as well as fixed AGP/PCI-clocks.
Additionally, the Nforce3 250/Gb features on-chip p-ATA and S-ATA RAID, eight USB 2.0 ports, on-chip Gigabit-Ethernet(independent from PCI-bus, Nforce3 250Gb only) and an on-chip Firewall.

Nvidia's Nforce3-chipsets all use a single-chip design(no North- and Southbridges, just one chip) – the Nforce3 150 is available on Socket 754 and a few Socket 940 motherboards while the newer Nforce3 2/Gb is currently available on Socket 754 and Socket 939 motherboards.

Just like VIA, Nvidia is planning to release a new, PCI-E enabled chipset in Q4 of this year – most likely, it will be called the Nforce4.
The Nforce4 will probably support a total of 32 PCI-E-lanes which would make two PCI-E 16x slots for SLI(dual Nvidia PCI-E videocards)possible.
Most likely, it will also support four on-chip S-ATA RAID channels(as well as p-ATA RAID capability), on-chip Gigabit-Ethernet, ten USB 2.0 ports, on-chip Firewall and high-definition,
'Azalia'-compliant audio(possibly called Soundstorm 2).

*Please be aware that all info about the upcoming Nvidia-chipset is based on rumors...the final products' specifications might be different from what is stated above*

More info about Nvidia-chipsets here' ">

SiS-chipsets are typically used on low-end/budget motherboards because they're usually priced lower than VIA or Nvidia-chipsets...more often than not, being implemented on rather low-end boards does limit the chipsets' potential.

Currently, SiS offers the SiS755 chipset for Socket 754 motherboards and SiS755FX chipset for Socket 939 motherboards – the only difference between these two chipsets is that the SiS755FX supports a 1000MHz(2000MHz effectively) Hypertransport-link, while the plain SiS755 only supports an 800MHz(1600MHz effectively) HT-link.
Both chipsets use the SiS964-Southbridge which communicates with the chipsets' Northbridge via 'MUTIOL 1G' at 1.0GB/s.
The SiS964-Southbridge features on-chip S-ATA RAID(2-channels), 6-channel audio(depending on external chip/codec) and eight USB 2.0 ports.

Additionally, SiS has a SiS760-chipset which is basically an SiS755(non-FX) with an integrated 'SiS Ultra 256' GPU(shared or dedicated memory).

SiS has already released a PCI-Express enabled chipset, the SiS756 – i am not currently aware of any motherboards available on the market that use this chipset, tho.

The SiS756 features a 1000MHz(2000MHz effectively) Hypertransport-link and one PCI-E 16x slot. The SiS965-Southbridge is connected to the Northbridge via 'MUTIOL 1G' and provides two additional PCI-E 1x slots, four on-chip S-ATA RAID channels, 8-channel audio, Gigabit-Ethernet as well as eight USB 2.0 ports.

More info about SiS-chipsets here' ">

Final words
Now what's the platform of choice for you?

Basically, it depends on what you need and what you can afford...of course, everyone wants a Socket 939 processor and a PCI-Express enabled motherboard, but bear in mind that this is a high-end platform that's going to cost you a lot more than a Socket 754 platform – also, you will still have to wait a few weeks or months until PCI-E enabled motherboards and chipsets actually hit the market, so if you need or want a new system now, a plain old AGP 8x motherboard will have to do(also, PCI-E videocards are no faster than their AGP-conterparts right now and it will prolly stay this way for awhile).

Here's a quick summary:

If you want the latest and greatest AMD Desktop processors, Socket 939 is the Socket for you – throughout this year and the next, AMDs' best will stay on this Socket...most likely, the first PCI-Express enabled motherboards for AMD processors will be Socket 939, too.

If you're looking for an affordable entry to the Athlon 64's world or if you simply want to replace your old system with a modern, powerful platform; even if you don't need or want 64-bit capability, Socket 754 is what you should look for.
Even if you insist on a 32-bit only processor, Socket 754 is still within your reach thanks to AMDs' new Sempron processors.

A Socket 940 platform is something to be considered for people who need a high-end workstation or Server or generally a system with more than one processor – only the Opteron 2xx and 8xx series support multiprocessor configurations.
Athlon 64 and Athlon 64 FX processors are for uniprocessor(single-CPU) systems ONLY.
Also, bear in mind that ALL Socket 940 processors require registered memory.

This is mostly a question of price and personal preference - performance-wise, all these chipsets are so close to each other it doesn't really make a difference.

If you're on a very limited budget, you will probably opt for a motherboard with an SiS or VIA chipset since these tend to be noticably cheaper than boards based on Nvidia-chipsets.
Right now(August 2004), Nvidia's Nforce3 250Gb chipset offers the best set of features for both Socket 939 and Socket 754 motherboards.

rev. 1.0 – 08/23/2004

Note: The info presented above is to the best of my knowledge – if you have any questions, comments, criticism, feel free to PM me.

The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.

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