AMD FX Series Hypertransport speeds

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Neon



Joined: 04 Feb 2008
Posts: 1512
Location: Dallas, Texas, USA

PostPosted: Sun Mar 25, 2012 9:46 am    Post subject: AMD FX Series Hypertransport speeds Reply with quote

What speed is the Hypertransport bus in the AMD FX Zambezi? There is conflicting information on AMD's website.

On the official product comparison site products.amd.com, it indicates System Bus 5200 MHz. This is impossible because HT 3.0 specification is maximum 3200 MHz = 6400 MT/s (MegaTransfers per second). So I think they mean 5200 MT/s = 2600 MHz.
http://products.amd.com/en-us/desktopcpuresult.aspx?f1=AMD+FX+8-Core+Black+Edition&f2=&f3=&f4=1024&f5=AM3%2b&f6=&f7=32nm&f8=125+W&f9=5200&f10=False&f11=False&f12=True

AMD FX Key Architectural Features webpage indicates "One 16-bit link at up to 5600MT/s"
http://www.amd.com/us/products/desktop/processors/amdfx/Pages/amdfx-key-architectural-features.aspx

AMD FX Processor Model Number and Feature Comparison webpage indicates "up to 4000MT/s full duplex"
http://www.amd.com/us/products/desktop/processors/amdfx/Pages/amdfx-model-number-comparison.aspx

AMD publication # 49686 Family 15h Models 00h-0Fh AMD FX™-Series Processor Product Data Sheet indicates "Maximum one (1) link on AM3r2 package, 16-bits in each direction, supporting up to 5200 MT/s (10.4 GB/s) in each direction in HyperTransport Generation 3.0 mode"
http://support.amd.com/us/Processor_TechDocs/49686.pdf

I think the last one is correct. Why is the website so wildly inconsistent?
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gshv



Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA

PostPosted: Sun Mar 25, 2012 1:10 pm    Post subject: Reply with quote

The first one (5200 MHz) is obviously wrong. I think they entered GT/s value into their database, which feeds products.amd.com, and forgot that the pages display MHz, and not GT/s Smile

The second one may reference maximum I/O bandwidth supported by the microarchitecture, or may be that they've also made a mistake.

4000 GT/s value in my opinion is a copy and paste error. I guess they copied specs from Phenom II page, and forgot to update HT and memory frequencies and bandwidth numbers. I wouldn't trust this page. DDR3-1866 should have bandwidth close to 30GB.

I think the 5200 GT/s value is correct. Product pages for Opteron 32500/3260/3280 (server versions of FX chips) all have 5200 GT/s. I also have one document with FX and earlier processor specifications that shows HT frequency as "up to 5200 GT/s".

By the way, HT speed on FX processor pages on CPU-World is also wrong. 2 GHz/2.2 GHz numbers that you see there are for NorthBridge frequency. This will be fixed later today.

Gennadiy
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Neon



Joined: 04 Feb 2008
Posts: 1512
Location: Dallas, Texas, USA

PostPosted: Sun Mar 25, 2012 1:42 pm    Post subject: Reply with quote

OK, those seem like reasonable explanations to me.

Thank you Gennadiy. Smile
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gshv



Joined: 01 Feb 2003
Posts: 7898
Location: Fairfax, VA USA

PostPosted: Sun Mar 25, 2012 3:18 pm    Post subject: Reply with quote

No problem. Thank you for pointing out the HT frequency mistake on FX-Series pages.

Gennadiy
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