From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2003-10-07 15:17:51
On Tue, Oct 07, 2003 at 01:46:08PM +0100, Peter Karlsson wrote:
> Daniele Gratteri:
>
> > Are the VIC 20 and the C64 tape routines exactly the same?
>
> Yes, but the timing differs slightly.
True. I made some measurements two years ago when I developed the
C2N232 and the c2n utility:
pulse width measurement unit = 8 MHz/64 = 125 kHz = 8 µs
/µs PAL VIC-20 CBM 8032SK PAL C64 PAL C128
short 37..42 (316±20) 41..46 (348±20) 45..50 (380±20) 48..53 (404±20)
medium 55..59 (456±16) 61..65 (504±16) 65..69 (536±16) 68..72 (560±16)
long 75..77 (608±8) 83..86 (676±12) 87..90 (708±12) 90..93 (732±12)
bck/MHz 1.108404 1 .940 (.985248) .920 (.985248)
> I have a nice article from a 1984 Swedish computer magazine suggesting
> that people that have problems reading C64 tapes from a VIC20 or vice
> versa use a PET as a "middle-machine", since its timings are somewhere
> in-between the two others.
Also true, as you can see above. I have no idea why the timings were changed
in the 128 mode of the C128. Do you?
Marko
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