当你升级你的计算机硬件时，你期望性能的提升是一个既定的事实，但有时你会得到出乎意料的显著增长，超出你所指望的。今天的超级用户问答帮助一个困惑但快乐的游戏玩家理解升级电脑内存时他是多么幸运。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

问题

超级用户读者CyberGhostx1想了解添加内存如何显著提高其电脑AMD APU的游戏性能：

To be clear from the start, this is not a problem. This is just something that I really want know the secret behind.

System Specs

• CPU: AMD A10-6790K 4.0 GHz
• GPU: AMD Radeon HD 8670D 1GB (integrated GPU)
• RAM: 2 x Team 4GB 1600 DDR3 = 8 GB

Of course, I am using a 64-bit OS to make use of my 8 GB of memory, but my question is: Before I installed the additional 4 GB of RAM, games like Mafia II ran (at the highest settings) at an average of 22 FPS. After I installed the additional RAM, I noticed a very decent increase to 40 FPS even though the game did not appear to use more than 4 GB of RAM.

What is the secret behind this?

游戏性能上的额外提升无疑是一种享受，但这次一个简单的内存升级是如何带来如此大的不同的呢？

答案

超级用户DragonLord和Ben Richards为我们提供了答案。首先，龙王：

I noticed you are using an AMD APU. These chips combine a CPU with a built-in graphics processor (GPU), eliminating the need for a discrete graphics card (at least for lighter workloads). Because AMD APUs use the system memory as graphics memory, integrated GPU performance is highly dependent on memory bandwidth. Not only does DDR3 system RAM have c***iderably less bandwidth than GDDR5 video memory (used on many discrete graphics cards), the integrated GPU needs to share this bandwidth with the CPU for normal application use. Increasing memory bandwidth will directly increase performance by reducing this bottleneck.

When you upgraded your system’s memory, you added a second memory module. With two modules, your memory now runs in dual-channel mode, doubling memory bandwidth and dramatically increasing performance as a result. Faster RAM (at least DDR3-1866, preferably DDR3-2100+) will similarly increase performance as well.

In addition, more memory means your system can pre-load more texture data into RAM, reducing the need to access the disk and increasing performance. However, this is less of a factor than the increased memory bandwidth.

To show how important memory bandwidth is for AMD APUs, websites such as Tom’s Hardware and PC Perspective have found that APU performance can increase with memory bandwidth up to at least DDR3-2100.

接着是本·理查兹的回答：

You have an APU, rather than a discrete CPU and discrete GPU. That means they share system RAM for texture cache, rather than dedicated on-board memory on a graphics card.

The reason the RAM upgrade sped things up for your game is likely because of texture resource swapping. With more RAM available overall, that means more texture data is able to be loaded and kept in RAM longer. When you have all your memory allocated, and your operating system needs more to work with for a task right now, it will find allocated memory that has not been used recently, save the contents to your disk, and then re-allocate the memory for that task. Once that data is needed again, it will swap it back from the disk into RAM. This swapping takes a long time (relatively).

You were likely swapping a lot on texture data. When you upgraded your RAM, you provided more space for textures to be stored, which means less memory swapping, which then translates into a higher FPS.

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