Interview Questions

1. If you have to write your own code (i.e. you do not have a library of memory components or a special component generation tool, what datastructures in VHDL would you use when creating a register file?
2. When using VHDL for an FPGA, under what circumstances is it better to write your own VHDL code for memory, rather than instantiate memory components from a library?
3. In this question there is a network that runs a protocol called BigLan. You are designing a router called the DataChopper that routs packets over the network running BigLan (i.e. they're BigLan packets). The BigLan network protocol runs at a data rate of 160 Mbps (Mega bits per second). Each BigLan packet contains 100 Bytes of routing information and 1000 Bytes of data.
   You are working on the DataChopper router, which has the following performance numbers:
   75MHz - clock speed
   500 number of clock cycles to process the routing information for a packet
   4 CPI for a byte of data
• Which has a higher maximum throughput router, and how much faster is it?
• Explain the effect of an increase in packet length on the performance of the DataChopper (as measured in the maximum number of bits per second that it can process) assuming the header
  remains constant at 100 bytes.
4. If performance doubles every two years, by what percentage does performance go up every month? This question is similar to compound growth from your economics class.

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