Originally posted by sanyombc555: Nope, 3.77 mhz is correct according to the original documentation and I believe I have read this elsewhere as well. Here is a sample: I thought it was strange at the time also.
Be careful, even original documentation can have errors. (One of the reasons I'm skeptical of 3.77 is because it looks so much like a typo, where the typist hit "3" instead of "4".)
However, that link you provided actually makes things clearer. If you read it carefully, the guy says the clock speed of his MBC-555 is 3.58 MHz. That value is actually much more believable. Here's why.
Computers designed to produce composite video signals compatible with NTSC television are generally based on a 14.31818 MHz fundamental clock, because the frequencies used in composite video are all submultiples of this frequency. Thus all the frequencies needed in the system can be generated by dividing this fundamental clock signal. For example, the IBM PC's 4.77 MHz clock speed is exactly 1/3 of this frequency. (IBM used a CPU chip with a 5 MHz spec, but clocked it at a slightly lower rate for video compatibility.)
Well, 3.58 MHz is exactly 1/4 of 14.31818 MHz. (OK, you'll be off in the 3rd and 4th decimal places, but these clock rates are rounded to begin with.) So Sanyo was clearly dividing their fundamental clock by 4 to generate the processor clock.
3.77 MHz, on the other hand, has no simple relationship with 14.31818 MHz, which is the other reason I was skeptical of that figure.