计算机内存是不稳定的，一旦断电，内存中存储的东西就会消失。但是，究竟为什么计算机内存是不稳定的呢？请继续阅读，我们将研究构建高速计算机内存的物理过程。

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Chintan Trivedi很好奇为什么计算机RAM必须是可变的：

If computer RAM was to be non volatile like other persistent storage [types], then there would be no such thing as bootup time. Then why is it not feasible to have a non volatile ram module? Thank you.

虽然有各种类型的非易失性RAM（称为NVRAM，在各种应用程序中都有，如在Wi-Fi路由器中存储数据），但Chintan特别提到PC中找到的RAM类型。究竟是什么阻止我们在桌面和笔记本电脑中使用NVRAM？

答案

SuperUser contributor MSalters提供了一些关于我们如何摆脱硬件的物理限制（无论规模多么微小）的见解：

Deep down it’s due to physics.

Any non-volatile memory must store its bits in two states which have a large energy barrier between them, or else the **allest influence would change the bit. But when writing to that memory, we must actively overcome that energy barrier.

Designer have quite some freedom in setting those energy barriers. Set it low 0 . 1, and you get memory which can be rewritten a lot without generating a lot of heat: fast and volatile. Set the energy barrier high 0 | 1 and the bits will stay put almost forever, or until you expend serious energy.

DRAM uses **all capacitors which leak. Bigger capacitors would leak less, be less volatile, but take longer to charge.

Flash uses electr*** which are shot at high voltage into an isolator. The energy barrier is so high that you can’t get them out in a controlled way; the only way is to clean out an entire block of bits.

换言之，要使RAM达到现代计算机操作所需的最高速度，唯一的方法就是保持状态变化之间的电阻极低（从而使RAM在断电的情况下变得易变并且容易被数据擦除）。

有什么要补充的解释吗？在评论中发出声音。想从其他精通技术的Stack Exchange用户那里了解更多答案吗？在这里查看完整的讨论主题。