An unganged dual-channel reminiscence interface consists of two impartial reminiscence controllers, every dealing with a 64-bit huge reminiscence channel. This method lets the processor execute two operations in tandem, given the accesses go to distinct reminiscence banks. On high of that it is now potential to learn and write on the similar time, one thing that is cannot be completed in 128-bit reminiscence mode. From a processor’s perspective DRAM could be very gradual, and what takes up more often than not (= latency), is opening the reminiscence and getting ready the learn/write operation – the precise information switch is pretty fast.
With two impartial reminiscence controllers these latencies may be mitigated, in a number of methods in unganged mode. While single-threaded workloads, or workloads that function on a comparatively small downside set, profit extra from ganged mode, unganged mode can shine when a number of (or multi-threaded) purposes work with huge quantities of reminiscence, which will increase the probability that two impartial banks of reminiscence get accessed. Perhaps unganged-aware software program, akin to OS-level reminiscence administration might assist take advantage of out of unganged mode, by making an attempt to unfold out processes evenly all through the bodily reminiscence, so impartial reminiscence accesses may be executed as usually as potential.
For built-in graphics, unganged mode is an actual killer software although. The iGPU reserves a bit of system reminiscence for geometry, textures and framebuffer. This reminiscence vary is often positioned on the finish of the bodily reminiscence area, whereas the Windows OS and purposes often are situated close to the beginning of bodily reminiscence. This successfully offers the GPU its personal devoted reminiscence controller, which additionally reduces reminiscence latency, as a result of one controller can maintain the IGP’s reminiscence pages open nearly on a regular basis, whereas the second controller takes care of the OS and software reminiscence requests.
AMD has been supporting unganged dual-channel reminiscence interfaces for over a decade now. The firm’s first Phenom processors launched unganged reminiscence with a BIOS choice to power the CPU to interleave all information, known as ganged mode. The consensus among the many tech-community over the previous ten years and the evolution of the fashionable processor towards extra parallelism favors unganged mode. With CPU core counts heading north of eight for mainstream-desktop processors, and built-in GPUs changing into the norm, it was pure for Intel so as to add assist for an unganged reminiscence interface.
