FIFO深度

最近，一直被这个问题困扰着。说是这个问题是面试时的热门问题，还说是没有一个固定的公式去算它。

有这么一个问题：

We have a fifo which clocks data in at 100mhz and clocks data out at 80mhz. On the input there is only 80 data in any order during each 100 clocks. In other words, a 100 input clock will carry only 80 data and the other twenty clocks carry no data (data is scattered in any order). How big the fifo needs to be to avoid data over/under-run.

解决方法：假设写入时为最坏情况，背靠背，即在160*1/100us内写入160个数字，而在这段时间内只能读出(160*1/100)*80个数据，这两个数的差为160*(1-8/10)=32。所以该FIFO深度为32。回答完毕