Re: What's the IIe's--Arghh!--MHz Speed?

[CUTjefbla@bconnex.net (Jeff Blakeney)]

On 23 Jan 1999 08:34:33 GMT, kentd@cup.hp.com (Kent Dickey) wrote:

>Here's some detail:

[some details snipped for brevity]

>The clock is divided by 14, giving 1.022727MHz, often rounded
>to 1.023MHz.  But wait, there's more.  A complexity involving the fact
>that the base Apple II clock and the video clock are strongly related
>means a quirk of NTSC video requires some adjustment to this clock
>circuit.  In short, every 65th 1MHz clock is stretched an extra 140ns
>(two 14MHz clocks) to make the video signal work correctly.

>The effective MHz is thus: (14318180/14)*(65*14/(65*14+2)) = 1.020MHz.

Well there you go.  I knew my memory wasn't failing on me yet.  :-)

However, I never heard about that stretching of the 65th clock cycle
before.  It is nice to know that there are still people out there with
even more Apple II information in their heads than me.  :-)

Thanks for the info.

=== To ensure I see a reply please also e-mail me but remember to:
    CUT the obvious from my e-mail address to e-mail me
    Jeff Blakeney - Dean of the Apple II University on Delphi
*** HyperCard IIgs course now in session in the A2Pro forum on Delphi