Phenom II X6 1090t - DDR3-2000 Speed Memory Speed too fast?

[forumguy]

I'm planning to build a Phenom II X6 1090t system soon. All items ordered except for memory.

I'm trying to decide between two speeds of memory: DDR3-1600 and DDR3-2000.

Newegg has the 1600 G.Skill for around $189 and the 2000 for $214

The Phenom II X6 has a HyperTransport speed of 2.0GHz. From my calculations, this gives a unidirectional max bandwidth of 16GB/sec. This is exactly the bandwidth speed of DDR3 2000 memory -- seems like a good match. But the maximum useable bandwidth of HyperTransport is reduced by bus overhead transactions and the memory is in a dual-channel configuration. So would I be wasting my money with DDR3 2000 memory being too fast for the bus?

 

[Jdawg84]

I'm planning to build a Phenom II X6 1090t system soon. All items ordered except for memory.

I'm trying to decide between two speeds of memory: DDR3-1600 and DDR3-2000.

Newegg has the 1600 G.Skill for around $189 and the 2000 for $214

The Phenom II X6 has a HyperTransport speed of 2.0GHz. From my calculations, this gives a unidirectional max bandwidth of 16GB/sec. This is exactly the bandwidth speed of DDR3 2000 memory -- seems like a good match. But the maximum useable bandwidth of HyperTransport is reduced by bus overhead transactions and the memory is in a dual-channel configuration. So would I be wasting my money with DDR3 2000 memory being too fast for the bus?

Get the fastest memory you can buy. Have you seen these?

http://www.newegg.com/Product/Produc...82E16820145317

 

[forumguy]

Get the fastest memory you can buy. Have you seen these?

http://www.newegg.com/Product/Produc...82E16820145317

Yes, I briefly looked at those -- nice CAS8 speed. But I plan to go to 16GB eventually and this Corsair Dominator kit would take up all my 4 memory slots to get my required 8GB total RAM. Nice fans on those but those little fans are probably sleeve bearings and end up not working within like 4 months -- my computers are always on.

 

[Arsynic]

If you're not overclocking, it doesn't make any sense to spend money on high performance memory.

 

[forumguy]

If you're not overclocking, it doesn't make any sense to spend money on high performance memory.

Not if the motherboard can set the FSB-to-memory clock ratio so you can get 2000 where you would otherwise normally get 1333 or 1600. I believe DDR3-2000 works out nicely with a 7.5 multiplier. Yes, all parts would still be running at "stock speeds" but just a faster stock. But are you confirming that the stock HyperTransport speed won't be able to fully utilize DDR3-2000 though? (refer to my original bandwidth calculations)

For the record, I plan to overclock my Phenom II X6 to 4.0GHz and beyond! Its the unlocked Black Edition and I'm undecided on whether to just increase the CPU multiplier or the FSB or a combination of both. Maybe I'll just do the CPU multiplier at first -- I've never had an unlocked CPU before.

 

[Jdawg84]

Why do you need 16GB of memory Bro?

 

[Arsynic]

Not if the motherboard can set the FSB-to-memory clock ratio so you can get 2000 where you would otherwise normally get 1333 or 1600. I believe DDR3-2000 works out nicely with a 7.5 multiplier. Yes, all parts would still be running at "stock speeds" but just a faster stock. But are you confirming that the stock HyperTransport speed won't be able to fully utilize DDR3-2000 though? (refer to my original bandwidth calculations)

For the record, I plan to overclock my Phenom II X6 to 4.0GHz and beyond! Its the unlocked Black Edition and I'm undecided on whether to just increase the CPU multiplier or the FSB or a combination of both. Maybe I'll just do the CPU multiplier at first -- I've never had an unlocked CPU before.

You didn't mention that you were going to overclock.

 

[forumguy]

Why do you need 16GB of memory Bro?

Two biggies that use up big memory on my setup: (1) need to run a virtual machine and (2) video editing. Even when working with photos, my ACDSee image processing software is using up like 400+ MB.

Also I've been using a virtual desktop system for many years now on Windows (XDESK). This lets you have multiple desktops like X-Windows. I look at other people's desktops, and they run out of desktop area and taskbar area before they run out of memory! For me, multiple desktops are almost like running multiple users simultaneously (multiuser OS). On one desktop, I have my video, another photo editting, another communications (email, IM) another the virtual machine, etc. This is how I use my desktop at home and I wouldn't have it any other way!

 

[dorion]

forumguy your memory isn't going of the HT link. AMD processors have a direct link to the memory through their integrated memory controller or some people call it the Northbridge now even though it is on die. The Northbridge runs at a different speed than the rest of the processor, and you can even overclock it beyond the normal overclocks you would get by overclocking the processor in general. In general higher Northbridge overclocks net you better performace because the IMC can handle more tranactions and your L3 cache is run off the Northbridge.

Also the general consensus on the net is to push for tighter latencies instead of DDR3 1600+ clocks an AMD platforms.

 

[forumguy]

forumguy your memory isn't going of the HT link. AMD processors have a direct link to the memory through their integrated memory controller or some people call it the Northbridge now even though it is on die. The Northbridge runs at a different speed than the rest of the processor, and you can even overclock it beyond the normal overclocks you would get by overclocking the processor in general. In general higher Northbridge overclocks net you better performace because the IMC can handle more tranactions and your L3 cache is run off the Northbridge.

Also the general consensus on the net is to push for tighter latencies instead of DDR3 1600+ clocks an AMD platforms.

Good point. I did not fully appreciate that the CPU's memory controller actually has a separate electrical path to the memory. Somehow, I always associated that the memory control logic was just built into the CPU but the physical path always went out the FSB. Now I understand why Intel copied AMD and are now using an onboard memory controller!

Say there is a choice between DDR3-1333 CAS7 versus DDR3-2000 CAS9. Which one is faster?

Certainly bandwidth of DDR-2000 is faster but what about latency? DDR3-2000 latency is 9 cycles (versus 7 cycles of DDR3-1333) -- apparently 29% slower! However DDR-2000's frequency is 50% faster, or put another way, its cycle is 4ns while DDR3-1333 cycle time is 6ns. So CAS latency of DDR3-2000 is 9 × 4ns = 36ns while DDR3-1333 is 7 × 6ns = 42ns. DDR3-2000 CAS9 latency is actually less than DDR3-1333 CAS7 latency?

 

[fffblackmage]

So CAS latency of DDR3-2000 is 9 × 4ns = 36ns while DDR3-1333 is 7 × 6ns = 42ns. DDR3-2000 CAS9 latency is actually less than DDR3-1333 CAS7 latency?

Yes.

 

[forumguy]

That's it... I'm splurging for the DDR3-2000 modules.

 

[Ben90]

Certainly bandwidth of DDR-2000 is faster but what about latency? DDR3-2000 latency is 9 cycles (versus 7 cycles of DDR3-1333) -- apparently 29% slower! However DDR-2000's frequency is 50% faster, or put another way, its cycle is 4ns while DDR3-1333 cycle time is 6ns. So CAS latency of DDR3-2000 is 9 × 4ns = 36ns while DDR3-1333 is 7 × 6ns = 42ns. DDR3-2000 CAS9 latency is actually less than DDR3-1333 CAS7 latency?

Yes.

7/1333*2000 = 10.5ns
9/2000*2000 = 9ns

 

[Makaveli]

Looks like these guys were following this thread

http://www.xbitlabs.com/articles/memory/display/phenom-ii-x6-ddr3-2000.html

 

[dorion]

Looks like these guys were following this thread

http://www.xbitlabs.com/articles/memory/display/phenom-ii-x6-ddr3-2000.html

Thats a good article for me to remember, makes me sad about my DDR3 memory once I upgrade from DDR2.

 

[fffblackmage]

Good point. I did not fully appreciate that the CPU's memory controller actually has a separate electrical path to the memory. Somehow, I always associated that the memory control logic was just built into the CPU but the physical path always went out the FSB. Now I understand why Intel copied AMD and are now using an onboard memory controller!

Say there is a choice between DDR3-1333 CAS7 versus DDR3-2000 CAS9. Which one is faster?

Certainly bandwidth of DDR-2000 is faster but what about latency? DDR3-2000 latency is 9 cycles (versus 7 cycles of DDR3-1333) -- apparently 29% slower! However DDR-2000's frequency is 50% faster, or put another way, its cycle is 4ns while DDR3-1333 cycle time is 6ns. So CAS latency of DDR3-2000 is 9 × 4ns = 36ns while DDR3-1333 is 7 × 6ns = 42ns. DDR3-2000 CAS9 latency is actually less than DDR3-1333 CAS7 latency?

Yes.

7/1333*2000 = 10.5ns
9/2000*2000 = 9ns

Crap, somehow, I didn't double check the numbers.

@Ben90 - Why did you multiply by 2000?

 

[Spikesoldier]

get a 1600 7-7-7 kit running the lowest vdimm. it is the best speed and timing you want to buy.

 

[taltamir]

you can get DDR3-2000 with an AMD system... BUT there are some limitations and strict requirements... read this:
http://www.xbitlabs.com/articles/memory/display/phenom-ii-x6-ddr3-2000.html

I don't think that the extra ram speed is worth it unless you have a specific business application that is heavily ram speed dependent (most apps don't benefit from faster ram at all, a few specific apps benefit a lot)