Confused about s754 Athlon64's and dual channel.

[Lorn]

I am very confused.

Why is it that socket 754 Athlon 64's cannot run dual channel RAM whereas an older socket A Athlon XP's can? If it is the motherboard that controls dual channel, then why don't they make s754 motherboards compatible with dual channel? I don't understand why a newer processor such as the s754 Athlon 64 isn't capable of this.

Any insight regarding the actual chips, motherboards or technologies would be very helpful. I'm just trying to understand this before I purchase an Athlon 64 system.

Also, is the difference between dual channel and single channel so profound that I should purchase a dual channel compatible Athlon 64 chip?

Thanks.

 

[bjc112]

Buy a 939 system..

Faster Hyper Transport / dual channel and X2 support!

 

[stevty2889]

Socket 754 doesn't support dual channel, the memory controller is on the proccessor itself, so you couldn't just make a socket 754 motherboard support dual channel. Dual channel doesn't have as much of a performance impact with A64's as it does with P4's as A64's aren't bandwidth strarved.

 

[Aenslead]

The core for A64 skt754 was designed for single channel memory configuration, hence, the less transistors and pins on the processors.

The skt939 is a tweaked skt940 without the need for registered memory.

The Socket A plataform depended on the chipset to determine if the processor could run @ dual or single channel. On any AMD64 artquitecture, be it sempron or opteron, or a64, regardless of the socket, the memory controller is on-chip.

Dual channel offers little advantage over single channel, but from an upgrade stance, your best bet is socket 939.

 

[Lithan]

Basically 754 doesnt have dual channel to make it cheaper and also to distinguish it from the "Premium" line so to speak (not so much anymore since the winchester 3200+ and 3000+ were released) of 939 processors.

I've never tested it myself but I'm told it's no more than a few % points in most Real world apps. Though it can be a HUGE difference in some benchmarks.

 

[Lorn]

Thanks for the help, guys.

 

[sangyup81]

Originally posted by: Lithan
Basically 754 doesnt have dual channel to make it cheaper and also to distinguish it from the "Premium" line so to speak (not so much anymore since the winchester 3200+ and 3000+ were released) of 939 processors.

I've never tested it myself but I'm told it's no more than a few % points in most Real world apps. Though it can be a HUGE difference in some benchmarks.

Yup, memory benchmarks. All synthetic stuff, no real world stuff.

 

[BitByBit]

The old Athlon XP 3200+, despite being dual channel, could only handle the bandwidth of one PC3200 Module due to its 400MHz 64-bit FSB, which basically means that a single-channel Athlon 64 can match, or even exceed the bandwidth of the XP (mainly thanks to its integrated memory controller).

 

[Aenslead]

Originally posted by: sangyup81

Originally posted by: Lithan
Basically 754 doesnt have dual channel to make it cheaper and also to distinguish it from the "Premium" line so to speak (not so much anymore since the winchester 3200+ and 3000+ were released) of 939 processors.

I've never tested it myself but I'm told it's no more than a few % points in most Real world apps. Though it can be a HUGE difference in some benchmarks.

Yup, memory benchmarks. All synthetic stuff, no real world stuff.

Indeed. Sandra and PC Mark show such increase. There is an article on AT about socket 939; you'll see that a 3400+ skt 754 performs exactly the same as a 3500+ skt 939.

 

[Sentential]

S754 CPUs lack the full 939 pins which would allow the memory controller to use dual-channel RAM.