QUESTION If IEI* is tied low (as opposed to being asserted as shown in Figure 7-7 in the MC68901 manual), how many clocks should it take for the MC68901 to respond to an interrupt acknowledge cycle? ANSWER Due to the age of the MC68901, it is not possible for Motorola to answer questions which require input from the original designers. However, it is not recommended that the MC68901 be run synchronously, because our specs guarantee asynchronous operation only. It is the responsibility of the system designer to monitor the DTACK* signal of the MC68901 to ensure proper operation.