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Venice core memory controller question

F

Fuelrod

Senior member
According to this article:

AMD engineers promised to eliminate this problem in the new Venice core and they did keep their word. Athlon 64 processors based on Venice can work with four single-side DDR400 SDRAM modules without any limitations, and if there are double-side DDR400 SDRAM DIMMs installed, they can work at 400MHz with 2T timing.
Click to expand...

What is it about double-sided DIMMS that cause then to have to be run at 2T. The trace lengths can't be much longer. How about power consumption, does a double-sided 512 DIMM need more power than a single-sided 512 DIMM? Help me understand.

I'm a little frustrated because I have some Mushkin Blue double-sided 2x512 sticks and I thought if I upgraded to the Venice core I could get another pair without penalty. Now it doesn't look like that will happen. Also it seems to me most memory that I've seen is double-sided so the Venice core "four DIMM fix" seems hollow.
 
The Venice does actually fix some stuff, though; with the last revision four DIMMs required dropping 333DDR instead of 400DDR.

As for why, I don't have a clue. 🙁
 
The 2T command rate should been the issue they worked on. I would think that's more important than being forced to run at DDR333 over DDR400.
 
I have a question. I currently have 2 512MB PC3200 sticks of RAM myself, and when I upgraded to a Venice A64 this summer, I was thinking about adding a second gigabyte of RAM. What would be the best way to do this? Could I just add one 1GB stick and keep DDR400 and 1T command rate? Also, would it remain in dual channel...?
 
Originally posted by: SynthDude2001
I have a question. I currently have 2 512MB PC3200 sticks of RAM myself, and when I upgraded to a Venice A64 this summer, I was thinking about adding a second gigabyte of RAM. What would be the best way to do this? Could I just add one 1GB stick and keep DDR400 and 1T command rate? Also, would it remain in dual channel...?
Click to expand...


No... 3 DIMMS are unsupported in most (if not all) S939 motherboards. So your choices are 4x512MB DIMMs at 2T or 2x1GB DIMMs at 1T. Generally the 2x1GB DIMMS will be faster. Nothing currently available will be as fast as decent 2x51MB DIMMs in raw speed and OC potential though.
 
Originally posted by: Avalon
The 2T command rate should been the issue they worked on. I would think that's more important than being forced to run at DDR333 over DDR400.
Click to expand...


For the ppl who really need this amount of ram the only hit is on bandwidth, which I though t we all agreed didn't mean as much...right??? I can run near 600dr now at 296HTT with cas 3-4-4-11 but need 2t to get stable.....The difference is like near 8000 in bandwidth if I could get it stable but still get near 7000's with it at 2t...I dont think that is a real problem and far better then anything at stock...

So in the end Ocers will be able to work around this by just clocking high enough to overcome it versus stock speeds...stock users may drop down a bit, but how much of a detrimnetal effect in % is there??? And for those type of users that use 2gb (gamer really dont need it) they tend not to be big bandwidth dependent apps...It doesn't seem to improve my premier times in video editing but I am sure 2gb would be appreciated by the app while doing editing...it is the cpu that drives my performance of rendering at the end...
 
Originally posted by: Concillian
Originally posted by: SynthDude2001
I have a question. I currently have 2 512MB PC3200 sticks of RAM myself, and when I upgraded to a Venice A64 this summer, I was thinking about adding a second gigabyte of RAM. What would be the best way to do this? Could I just add one 1GB stick and keep DDR400 and 1T command rate? Also, would it remain in dual channel...?
Click to expand...


No... 3 DIMMS are unsupported in most (if not all) S939 motherboards. So your choices are 4x512MB DIMMs at 2T or 2x1GB DIMMs at 1T. Generally the 2x1GB DIMMS will be faster. Nothing currently available will be as fast as decent 2x51MB DIMMs in raw speed and OC potential though.
Click to expand...

Interesting...I didn't know that! I'm still not sure if I want to go to 2GB (I've had 1GB since August 2003), but if I do decide to do that, maybe it would be better to sell my current RAM and get 2 1GB sticks...

Edit: Why is it specifically that this particular configuration (3 DIMMs) won't work?
 
Originally posted by: SynthDude2001
Originally posted by: Concillian

No... 3 DIMMS are unsupported in most (if not all) S939 motherboards. So your choices are 4x512MB DIMMs at 2T or 2x1GB DIMMs at 1T. Generally the 2x1GB DIMMS will be faster. Nothing currently available will be as fast as decent 2x51MB DIMMs in raw speed and OC potential though.
Click to expand...

Interesting...I didn't know that! I'm still not sure if I want to go to 2GB (I've had 1GB since August 2003), but if I do decide to do that, maybe it would be better to sell my current RAM and get 2 1GB sticks...

Edit: Why is it specifically that this particular configuration (3 DIMMs) won't work?
Click to expand...

I do not know why specifically. My nForce2 supported 3 DIMMs in dual channel. I would guess the memory controller on the S939 A64s simply doesn't support it. If you look at manuals for S939 boards (downloadable from MFR sites), you'll see that they make it pretty clear that 3 DIMMs is unsupported. 1 and 2 are supported in single channel and 2 and 4 are supported in dual channel, but 3 is a no go.
 
You guys need to actually read some motherboard reviews:
http://www.anandtech.com/mb/showdoc.aspx?i=2358&p=7
"Tests with all four DIMM slots populated on the DFI nForce4 boards required a 2T Command Rate with 4 DS DIMMs in two dual channels. This is the pattern seen on other top-performing Socket 939 boards, but we hoped higher voltage might allow us to eek out 4 DS DIMM 1T performance. However, additional voltage did not help and DDR400 with 4 DS DIMMs still required a 2T Command Rate on the DFI nForce4 boards."

A similar pattern is found for most nforce4 motherboards using that processor (a clawhammer 4000+). Notice that is a clawhammer chip (ie first a64 core) already running 4 ds dimms at ddr400 at 2T. If there have been any improvements to the winchester and venice memory controllers (which there have been several articles showing there have been), one of them might be to allow a 1T command rate with 4 ds dimms. We'll just have to wait for someone with a venice to actually check.
 
Originally posted by: SLIM
You guys need to actually read some motherboard reviews:
http://www.anandtech.com/mb/showdoc.aspx?i=2358&p=7
"Tests with all four DIMM slots populated on the DFI nForce4 boards required a 2T Command Rate with 4 DS DIMMs in two dual channels. This is the pattern seen on other top-performing Socket 939 boards, but we hoped higher voltage might allow us to eek out 4 DS DIMM 1T performance. However, additional voltage did not help and DDR400 with 4 DS DIMMs still required a 2T Command Rate on the DFI nForce4 boards."

A similar pattern is found for most nforce4 motherboards using that processor (a clawhammer 4000+). Notice that is a clawhammer chip (ie first a64 core) already running 4 ds dimms at ddr400 at 2T. If there have been any improvements to the winchester and venice memory controllers (which there have been several articles showing there have been), one of them might be to allow a 1T command rate with 4 ds dimms. We'll just have to wait for someone with a venice to actually check.
Click to expand...

But what is that with 4 single sided DIMMs?
 
Originally posted by: SLIM
If there have been any improvements to the winchester and venice memory controllers (which there have been several articles showing there have been), one of them might be to allow a 1T command rate with 4 ds dimms. We'll just have to wait for someone with a venice to actually check.
Click to expand...

Feedback coming from the engineering samples of the Venice core that went out indicate that 4 single sided DIMMs works at 1T, but 4 double sided DIMMs still require 2T with Venice.

So for performance purposes, 2GB will cause a performance hit either way. Either it will be 4x512MB DIMMs at low latency but 2T command rate, or it will be 2x1GB DIMMs at 1T command rate, but higher latency.
 
I have 4 duobule sided 512MB dimms (corsair valueram 2.5)..

It seems that my EPOX NF4 Board (cpu is a venice 3000+) sets the RAM speed to 166 mhz instead of 200.. Is this by design?

i'm a damned amd memory controller newb.
 
In General the best way to avoid problems with 939 boards is that u only use two memory modules. Or u need single-sided Modules which are rare and expensive.
 
I've got 4 single sided (256mb) Dimms, and it still runs 2T.

Venice 3800+
Asus A8V Deluxe
4 x 256mb Geil PC4000

Not overclocked......yet.
 
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