威盛(VIA)的一道考题,求解!

mengyu

一个异步FIFO 为N*64

题干为:

parameter:

1)Bus's clock is 500Mhz,width is 16 bit.

2)The tipycal data payload packet is 8QW,the ACK packet is 2 DW.

3)The latency from receiver receiving the complete data packet to send out the ACKpacket is 20ns.

4)The throughput of transmitter FIFO's input and output is equaled.

Caculate the optimized FIFO depth N?

怎么算深度N啊???    参数8QW和2 DW是什么意思?  请好心人仔细的指点一下!!!!