Posted 04/21/2009 at 02:30:14pm

Obviously you TOTALLY misunderstood. I bought an I7 920 because it is faster and was just wanting clarification on what was said versus what I read. The only whining I hear is you.

Posted 04/18/2009 at 01:07:29am

Please clear something up for me you stated in your article "AMD fans, of course, will point out that the fastest iteration of AMD’s chip-to-chip conduit, dubbed HyperTransport 3.1, is twice as fast as the current QPI." But I just read a rather lengthy explanation that seems to make that a false statement. I don't know how to shorten it so I'll just put it in here and let you tell me which is right. Sorry it's long but it says QPI is 78% faster than the fastest Hypertransport Technology.

The first version of the QuickPath Interconnect will work with a clock rate of 3.2 GHz transferring two data per clock cycle (a technique called DDR, Double Data Rate), making the bus to work as if it was using a 6.4 GHz clock rate (Intel uses the GT/s unit – which means giga transfers per second – to represent this). Since 16 bits are transmitted per time, we have a maximum theoretical transfer rate of 12.8 GB/s on each lane (6.4 GHz x 16 bits / 8). You will see some people saying that the QuickPath Interconnect has a maximum theoretical transfer rate of 25.6 GB/s because they simple multiply the transfer rate by two to cover the two datapaths. We don’t agree with this methodology. In brief, it is as if we said that a highway has a speed limit of 130 MPH just because there is a speed limit of 65 MPH in each direction. It makes no sense.

So compared to the front side bus QuickPath Interconnect transmits fewer bits per clock cycle but works at a far higher clock rate. Currently the fastest front side bus available on Intel processors is of 1,600 MHz (actually 400 MHz transferring four data per clock cycle, so QuickPath Interconnect works with a  base clock eight times higher), meaning a maximum theoretical transfer rate of 12.8 GB/s, the same as QuickPath. QPI, however, offers 12.8 GB/s on each direction, while a 1,600 MHz front side bus provides this bandwidth for both read and write operations – and both cannot be executed at the same time on the FSB, limitation not present on QPI. Also since the front side bus transfers both memory and I/O requests, there are always more data being transferred on this bus compared to QPI, which carries only I/O requests. So QPI will work “less busy” and thus having more bandwidth available.

QuickPath Interconnect is also faster than HyperTransport. The maximum transfer rate of HyperTransport technology is 10.4 GB/s (which is already slower than QuickPath Interconnect), but current Phenom processors use a lower transfer rate of 7.2 GB/s. So Intel Core i7 CPU will have an external bus 78% faster than the one used on AMD Phenom processors. Other CPUs from AMD like Athlon (formerly known as Athlon 64) and Athlon X2 (formerly known as Athlon 64 X2) use an even lower transfer rate, 4 GB/s – QPI is 220% faster than that.

Thanks 

John W

Posted 01/12/2008 at 03:17:04pm

This is great. I love your Mag. After subscribing to all the others for the past 20 years yours is the only one I still subscribe to because of the fresh articles and it's a power users mag. Just upped for 2 more yrs, showing I'm not just talking. JW