First of all, notice that you are potentially doing a lot of unnecessary work when the buffer runs out, since you are processing two buffers for each loop iteration.
首先注意，当缓冲区用尽时，可能要做许多不必要的工作，因为对于每个循环迭代都要处理两个缓冲区。
2
You then use register 127 as your loop counter and register 126 as your base pointer, and perform convert_to_upper on each value until you get to the end of the buffer.
As shown in Figure 2-9, the guard buffer significantly reduces the charging time of CSHUNT because of the open-loop gain (AGUARD), which is typically 104 to 106.