Re: [hatari-users] Floppy in Falcon mode

[Thomas Huth <th.huth@xxxxxx>]

Am Mon, 26 Dec 2011 00:07:14 +0100
schrieb Nicolas Pomarède <npomarede@xxxxxxxxxxxx>:

> On 25/12/2011 22:50, Vincent Rivière wrote:
> 
> > I measure the time taken for the Restore command by using Hatari's
> > VBL traces between "fdc type I restore" and "fdc complete command".
> > On Falcon it is (156 - 12) = 144 VBLs which means 2.4 seconds at 60
> > Hz. According to fdc.c, it should be 1.2 second (1.2 second for
> > motor on and ~0 second for Restore from track 0).
> >
> > So it seems that the FDC delays are twice as expected in Falcon
> > mode. This is enough to explain all my trouble.
> 
> I barely use the Falcon mode, so I never noticed this.
> 
> In fact, the Falcon Ajax FDC uses a 16 MHz clock, while other ST
> models use a 8 MHz, and a stated in FDC_DelayToCpuCycles, FDC_Freq is
> expected to be the same as CPU_Freq (ie 8 MHz) for correct timings
> calculation.
> 
> So, on Falcon converting an FDC delay from microsec to cpu cycles 
> returned twice the expected value. This is now corrected, I added a 
> special case for Falcon to correct the cpu cycles.

Great that this problem is fixed. But what about TT mode? Didn't the TT
have an Ajax chip, too? If yes, which frequency did it use?

 Thomas