Re: [stella] tutorial progress

Subject: Re: [stella] tutorial progress
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Fri, 28 Jun 2002 16:18:41 +0200
> 228 Clock Counts / 3 = 76 Machine Cycles
> But according to the SPG, the 228 is split between 68 and 160.
> I thought it was safer to round down for both (hence 22 and 53)
> but if rounded normally, it would be 23 and 53, not 22 and 54.
> Perhaps some hardcore cycle counter has an opinion on which one
> of those is more accurate, or if my conservative rounding down
> strategy is the best bet.  

The problem here is that the horizontal blank ends in the
middle of a processor cycle. At cycle 22 you are 2 pixels
before the display starts, and at cycle 23 you are already
1 pixel into the display.

But if your are accepting the object positioning logic as
a reference, then it would be 22 and 54. For example
hitting RESP0 during the horizontal blank will position
player 0 as if the access to RESP0 ended at cycle 22.

Ciao, Eckhard Stolberg

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