On 11/2/2012 9:56 PM, Charles Kroeger wrote: > On Wed, 31 Oct 2012 12:30:02 +0100 > Stan Hoeppner <s...@hardwarefreak.com> wrote: > >> Now if they'd just smarten up > > I've pondered this sort of thing my whole adult life. I don't understand > everything > you're saying here but it sounds pretty straight forward for someone who > does, like > the 50 miles-to-the-gallon carburettor only that was just a myth, your > description > sounds actually plausible. I guess adding cores without adding anything else > would > be a way to get higher prices for the new and better, makes sense to me, > that's pure Harvard Business School. We've come to the truth of it.
This was all written about at great length some 10 years ago when all the CPU vendors started implementing Simultaneous Multi-threading (SMT), called HyperThreading by Intel marketing wizards, and/or multiple CPUs (cores) per silicon die. The die is what most people call a "CPU". The reason the industry went the multi-core/SMT route was due to transistor physics, and had nothing to do with consumer workloads or demand. For any given process technology, whether 45/32/22 nanometer, there is a natural frequency speed limit, be it 3GHz, 3.8GHz, 5GHz, etc. Thus you can only make a single core go so fast by increasing clock speed. The downside to this method is power draw, which Intel famously ran into with its Netburst single core Pentiums and Xeons that ate over 100 watts at 3.8GHz. The rate of power draw, and thus heat dissipation, increases on a non-linear ever steepening curve as you increase frequency in a given process technology. For example, a 3.1GHz dual core chip produced on a 45nm process may have a TDP of 65 watts. If this die on this process could be pushed to 4GHz, the TDP would jump to somewhere around 100 watts, a 53% increase in power, while only increasing frequency by 18%. If we take the same die and add two more cores at 3.1GHz, our TDP is a little over 100 watts, about the same as the super clocked dual core. But, in this case we've increased effective clock rate by 100%, vs 18%, because we've doubled the number of cores. From a transistor standpoint this is a huge win for power vs instruction throughput. And for multi-process or multi-threaded server workloads this is great. However, for desktop end user workloads those extra two cores sit idle almost all the time, so there's no benefit. This is why I said it's a no-brainer for AMD to produce a dual core chip on 32nm and clock it as high as they can while staying around 100 watts. That should be somewhere around 4.6-5GHz. The fastest 45nm Regor die is currently 3.4GHz. That gives us a frequency increase of 35-47% for the same power as a 4 core version of the chip. But in this case desktop applications can actually make good use of this extra performance, whereas they don't make use of extra cores. Intel could be doing this already if they'd build an i3 22nm die sans the GPU. IBM was shipping 5GHz Power6 CPUs built on the 65nm process technology in 2008--4 years ago. 22nm transistors are capable of well over 7GHz frequency. An out of order branch predicting x86 dual core CPU based on Regor or Ivy Bridge would likely top out somewhere over 5GHz. AMD/Intel's latest quad core desktop offerings seem to top out around 4GHz. -- Stan -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/5095781d.2050...@hardwarefreak.com