What to Expect from AMD's Dual Core Processors

64-bit technology has recently taken the processor market by storm, but there’s another important change on the horizon for the x86 and x64 platforms that both Intel and AMD are introducing to their processor lines: dual core. Fundamentally, dual core is multiple processors on a single chip. I recently visited AMD to learn about their dual-core implementation. Below are answers to some of the questions you might have about this new technology.

1. What is dual-core technology?
   Dual core is two CPU cores on a single microprocessor chip. Your motherboard will have one socket, but the Windows task scheduler will show that you have two processors, and your applications will truly run in parallel as opposed to multitasking on a single processor.
2. How does dual core compare to Intel’s hyperthreading technology?
   Both technologies allow applications to run multiple threads simultaneously, but dual core chips provide a processor’s full capability to each thread simultaneously, whereas hyperthreading simply allows a second thread to use parts of the processor not in use by the first thread. Like AMD, Intel has also announced true dual-core technology in addition to hyperthreading.
3. What is multicore?
   Multicore refers to any processor with two or more cores on each chip. Although only dual-core processors will be available initially, AMD plans to support four and eight cores per chip in the future.
4. Do I need a new motherboard to use AMD’s dual-core processor?
   No, most motherboards designed for AMD processors will support AMD’s dual-core technology with a flash bios upgrade.
5. Do I need to upgrade my OS to use dual core?
   No, with some exceptions. Any symmetric multiprocessing (SMP) OS can support dual core, just as it supports multiple single-core processors. Both the 32-bit and 64-bit versions of Red Hat Enterprise Linux 4.0 have an incompatibility with the AMD dual-core bios that requires a patch to fix. Other OSs, such as Windows Server 2003, Windows XP, Solaris 10, Red Hat Enterprise Linux U1, and Novell SUSE Linux 9.2, support dual core out of the box.
6. Are existing OSs optimized for dual core?
   To best use multiple processors, including dual core, an OS must support Non-Uniform Memory Access (NUMA). Windows Server 2003 Enterprise, Windows XP Pro x64, Solaris 10 and some Linux distributions either support NUMA out of the box or can be configured to do so.
7. How does dual-core performance differ from multiple single-core processors?
   For the most part, single-core SMP-optimized applications will also be optimized for dual core. Dual core differs from single-core SMP because memory access occurs per-chip. This means that dual-core systems will have lower memory latency but also lower memory bandwidth. Each core on AMD dual-core chips will have a 128KB L1 cache (256KB/chip) and a 1MB L2 cache (2MB/chip), but future versions may also provide a shared L3 cache, further improving performance. As the technology matures, OSs might adopt process-scheduling algorithms that can take advantage of these differences to improve performance for each multiple-processor model.
8. Will my existing applications support and benefit from dual core?
   Any application that is multi-threaded will benefit from dual core. Because dual core is a processor technology, CPU-intensive applications, such as scientific processing, application servers, and databases will benefit the most from dual core. I/O intensive workloads, such as file servers, will benefit less. Applications that are not multithreaded, such as most games, won't benefit from dual core processors.
9. Are there any programs that won’t work with dual core?
   Some programs that claim to support multiprocessing might have been designed to support only two processors and may fail on a machine with two dual-core processors. These programs will need to be modified, just as they would need to be modified for a four-way single-core machine.
10. Will I need a multiple processor license to run my application or program on a dual-core processor?
    Software licensing for dual-core processors will vary from vendor to vendor. Microsoft, Red Hat Linux, and Sun have pledged to support each dual-core chip with a single license. Oracle and IBM require one license per core rather than per chip.
11. Will dual-core chips have higher power requirements?
    AMD’s dual-core processors have the same power envelope as single-core systems To accomplish this, dual-core systems run at lower clock speeds than their single-core counterparts. AMD’s dual-core systems will run between 1.8GHz and 2.2GHz. This means that non-multithreaded applications, such as games, will run slower on a dual-core system than on a similarly priced single-core system. Other single-threaded applications that aren’t CPU intensive, such as Microsoft Word, will have neither a performance increase or decrease on dual-core systems.
12. How do I know whether a particular AMD processor model is dual core?
    AMD model numbers for their dual core processors increase in multiples of five. So, for example, dual-core Opteron 800 series will have model numbers of 865, 870, and 875.
13. Will dual core really improve overall performance or will I just run into I/O bottlenecks?
    AMD claims that hypertransport, the bus technology that connects the processor to the rest of the computer, supports far more bandwidth than AMD’s current processor can use, so as many as 4 cores will not be limited by bandwidth constraints.
14. How much will dual-core chips cost?
    Pricing for AMD’s lower clock speed dual-core chips will be similar to higher clock speed single-core chips, making dual core a trade off between clock speed and multiprocessing. For example, both the single-core 2.6GHz AMD Opteron 152 and the dual-core 1.8GHz Opteron 165 will cost $637. You’ll need to consider how much your applications will benefit from multiprocessing to determine what is the best value for your environment. Because AMD’s dual-core processors support the same motherboards as single-core processors, you’ll be able to pack a lot more processing power into the same form factor, an obvious benefit if rack space is tight.
15. What AMD CPU lines will have dual-core versions?
    AMD plans to support dual core in all of its CPU lines, including Opteron, Athlon, Sempron and Turon. AMD will not initially offer a dual-core version of the Athlon FX line because of its popularity in the game market and the lack of multithreading support in most games.