How Much Video Processing Performance Boost Do the Latest PC Processors Deliver?

早在2009年, when HP shipped new workstations powered by the Nehalem line of CPUs, the performance boost was so significant that they instantly rendered obsolete workstations based upon previous architectures. Now that Intel has launched Ivy Bridge-based CPUs that triple the core count of early Nehalem-based workstations from four to 12, 我们能期待类似的性能提升吗? 这就是我将在本文中探讨的内容, which compares the performance of a 12-core (24 with HTT) 惠普Z800 against a 24/48 core HP Z820 in both editing and streaming encoding functions.

Z800，我 综述了 EventDV in 2010，合并了两个3.33GHz X5680 Xeon processors, with 24GB of RAM running the 64-bit version of Windows 7. 显卡是NVIDIA Quadro FX 4800，带有1.5GB的专用内存和3的访问权限.增加5GB系统内存.

Z820 (下面的图1)包括两个2.7 GHz E5-2697E CPUs, with 64 GB of RAM also running Windows 7. Graphics is supplied by an NVIDIA Quadro K5000 with 4 GB of video RAM. 凭借其更新的架构, the Z820 also enjoys a faster system bus than the Z800 (8 GT compared to 6.4GT), faster memory (1866 MHz compared to 1333 MHz) and one additional memory channel (3 vs. 4), all contributing to a greater maximum memory throughput of 59.7 GB/sec (Gigabypres per second) compared to 32 GB/sec for the Z800.

图1. Z820在外观上没有太大变化.

Though there are some minor hardware differences inside the box, HP did not retool the enclosure for its latest workstation generation. 把Z800放在Z820旁边，模糊产品名称, and only the most eagle-eyed observer will be able to tell them apart.

设定的期望

我所有的测试都是渲染测试, and the key question was how much faster the Z820 would perform than the Z800, which I measured as the percentage reduction in rendering time. 如果Z800花了10分钟渲染一个项目, 而Z820只花了5分钟, Z820将渲染时间缩短了50%(10分钟-5分钟/10). 性能提升多少是合理的预期?

让我们从简单的理论开始. 因为Z820的内核数是Z800的两倍, 用一半的时间完成同样的工作听起来很合理, 让50%的目标看起来是可以实现的. 然而，由于Z800上的cpu大约快了20% (3.33 GHz和2 GHz相比.7 GHz), each core should operate about 20% faster, cutting the 50% down to about 40%. 然而, 在涉及大量数据的任务上, 比如RED和4K项目, the faster memory bandwidth of the Z820 should also pay some performance dividends.

So, theory would suggest that the Z820 should perform between 40-60% faster, 取决于任务. 这是一个很好的起点. 然而, keep in mind that just because there are 48 cores doesn’t mean that all tasks are efficiently split over those 48 cores. 举个例子， 图2(下面) shows the Performance tab of the Windows Task Manager on the Z820 while encoding a single file using the VP6 codec in the Adobe Media Encoder. You can see this view on any Windows computer via the three-finger salute (Ctrl-Alt-Delete), 选择Windows任务管理器, 然后单击Performance选项卡.

图2. Windows任务管理器的这种视图让英特尔的工程师们哭了.

为什么CPU利用率这么低? Because the VP6 codec is licensed from On2 (or what formerly was On2) and it’s always been highly inefficient from a multiprocessing perspective, meaning that it doesn’t make efficient use of additional CPU when available. That’s largely because VP6 was developed before multicore computers were widely available, and was put out to pasture before it made sense to update the code to take advantage of multiple cores.

我的所有测试都不涉及输出到VP6. The high-level point is that multicore efficiency varies from program to program, 甚至是程序内的任务对任务. If a task is particularly inefficient from a multicore perspective, Z800的cpu时钟速度更快(3).3 Ghz) would be a bigger advantage than the extra cores on the Z820 with the slower CPU speed (2.7 Ghz). 除了, even when a program does effectively split operation over multiple cores, 这涉及到一些开销和管理, which poaches resources away from the rendering or other operation taking place.

因为这些原因, 当一个特定的程序, 或程序中的函数, doesn’t come close to harvesting the theoretical performance benefits the additional cores would seem to make available. This is particularly so with applications such as Premiere Pro, 它使用一系列第三方编解码器与DV一起工作, 丁肝病毒, AVCHD, and the alphabet soup of other codecs presented by the various input formats. Since a program can never be faster than its slowest operation, 如果这些编解码器的编写效率低下, 他们会拖慢整个行动.

OK, now that our expectations are set, looks move on to our tests.