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Gigabyte: the system bus speed will downgrade from HT3.0 to HT1.0 spec

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  • Motherboards
  • CPUs
  • Gigabyte
Last response: in Motherboards
July 26, 2011 8:11:43 AM

I've been reading on the Gigabyte GA-M68MT-S2P Mobo's specs:
[1] http://www.gigabyte.com/products/product-page.aspx?pid=...

In its CPU support description, it states:

Quote:
Supports next generation of 45nm AMD AM3 CPU This motherboard features Split Power Plane, 4+1 phase VRM to support AMD's latest 45nm AM3 Athlon II/ Phenom II series processors, delivering greater performance enhancements and the ultimate in hardware scalability.

* If you install AMD AM3 CPU on this motherboard, the system bus speed will downgrade from HT3.0 (5200MT/s) to HT1.0 (2000 MT/s) spec; however, the frequency of AM3 CPU will not be impacted. Please refer "CPU Support List" for more information.


Can anyone explain what this means? I'm looking at the 'Low' category build in the Logical Increments PC Buying guide ( http://tinyurl.com/TheFalconGuide ) (AMD Athlon II X3 445 3.1 GHZ CPU + HD 6670 GPU) and would like to buy this motherboard instead of the ones suggested in that guide (due to it being cheaper than the mobos suggested in the guide, and I believe, is compatible with the other parts). I'm just not sure what that statement means.

More about : gigabyte system bus speed downgrade ht3 ht1 spec

a b V Motherboard
a b à CPUs
July 26, 2011 3:57:39 PM

The HT link is the link between the CPU and the Chipset. Generally as long as it's at 1Ghz and above it's fine as HT link speed is the last thing to affect performance. Officially, HT 1.0 and 1.1 only go up to 800MHz but AMD kinda broke that by running their AM2 CPUs at 1000 MHz (o.k you don't care ^_^). Anyway it's likely that the board needed a lower HT link speed to ensure compatibility with AM3 CPUs. You can manually raise the HT link multiplier in the BIOS so you should be able to run it stable at 1800MHz and 2000MHz (using 9x and 10x respectively)
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a c 122 V Motherboard
a c 96 à CPUs
July 26, 2011 3:58:33 PM

AM3 CPUs can have a faster Hyper-Transport link between the CPU and the chipset.

That outdated board cannot support the faster HT link. The CPU will still work at its normal speed, but that HT link will be slower because the board can't handle it. The boards they recommend on that Low listing do support the full faster HT speed.

Would you notice the difference? Probably not, as the HT speed isn't usually a bottleneck.
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a c 122 V Motherboard
a c 96 à CPUs
July 26, 2011 4:01:02 PM

megamanx00 said:
Anyway it's likely that the board needed a lower HT link speed to ensure compatibility with AM3 CPUs. You can manually raise the HT link multiplier in the BIOS so you should be able to run it stable at 1800MHz and 2000MHz (using 9x and 10x respectively)

The board is outdated -- it can only run HT 1.0 speed no matter which CPU is installed. There will not be an option to run it faster than 2000MT/s (1000MHz).
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a b V Motherboard
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July 26, 2011 4:30:19 PM

Leaps-from-Shadows said:
The board is outdated -- it can only run HT 1.0 speed no matter which CPU is installed. There will not be an option to run it faster than 2000MT/s (1000MHz).


Check the link. The board itself can run with a 2000 MT/s HT which means it can run at the appropriate HT multiplier (10x) to do so. If the BIOS has the option to change the HT link multiplier, then it can be manually set above the 1000 it defaults to when an AM3 CPU is installed. It should of course be tested for stability since it goes to a lower HT speed for a reason :D 
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July 27, 2011 11:25:47 AM

Leaps-from-Shadows , megamanx00

Thanks for clearing that one up.

megamanx00 said:
Anyway it's likely that the board needed a lower HT link speed to ensure compatibility with AM3 CPUs. You can manually raise the HT link multiplier in the BIOS so you should be able to run it stable at 1800MHz and 2000MHz (using 9x and 10x respectively)

Would you recommend that I manually raise the HT link multiplier? What are the risks and advantages? And which outweighs which?
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a c 122 V Motherboard
a c 96 à CPUs
July 27, 2011 4:25:57 PM

mega:
I think we're getting crossed up here on terms. Manufacturers artificially inflate the speeds by quoting the number of transfers (MT/s) going both ways at once. It's already at the maximum speed (1000MHz times two directions equals 2000MT/s). A brand new 990FX board supports HT 3.1 for Bulldozer, so 3200MHz times two directions equals 6400MT/s.

dazed:
You won't be able to increase the multiplier. It is already operating at the maximum speed on that outdated board. Again, the reason they recommend those more expensive boards is that they support the full HT link speed of the AM3 processors.
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a b V Motherboard
a b à CPUs
July 27, 2011 5:49:48 PM

Ah, you're right. I see the error of my ways. I forgot about the whole MT thing, darn marketing :p .
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a b V Motherboard
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July 27, 2011 5:53:07 PM

Hmm... so yeah running the HT link higher wold be running it out of spec. I doubt then that your board would have higher multipliers but it might. In my experience the biggest problem in running the HT link higher is heat especially on those nVidia chipsets. You can put a small fan on the chipset though, but it seems like alot of effort considering the effect on performance from just the HT link is very small (as long as it's 1Ghz or over).
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