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Old 14 May 2014, 10:31   #388
Digital Corruption
RedskullDC's Avatar
Join Date: Jan 2007
Location: Sydney/Australia
Age: 53
Posts: 294
Hi Ikonsgr, et al.
Originally Posted by ikonsgr View Post
I kind of "prove" this my self, by testing the 68000/14Mhz hack on my A500. Using a real drive didn't work because of the double speed of "E" signal which drives the I/O CIA chips, that affect all the electro mechanical signals of the floppy. But when i tried using gotek, it worked fine!
With the 14MHz hack, the timing loops on the track stepping for the floppy are running twice as fast. Violates the minimum track stepping pulse width requirement of a "real" floppy drive.

Gotek effectively has a track to track access time of ZERO ms, so doesn't have the same requirements.

Originally Posted by ikonsgr View Post
So what i'm asking is, if the way to achieve double speed on a usb floppy emulator ONLY (and not a real drive where much more issues emerge), is changing some settings of the gotek firmware, or there is an "unbeaten" limit of the max speed paula can encode/decode mfm data stream!
Check your A500 schematic.
Paula chip is clocked by CCK and CCKQ (staggered 3.5MHz clocks) , and *not* by the 'E' clock.
This is why it still works with the 14MHz hack active.

It also means it you are stuck with the 250kbps transfer rate (or 125kbps in the so called faulty chips).
At the moment, that means DD (880kb) disks only.

I would imagine it is possible to make the firmware in the Gotek boards emulate the half speed transfer rate of the Chinon FZ-357a drives, to give HD floppy compatibility.

I guess we will know for sure when H.M. releases his source code


Last edited by RedskullDC; 14 May 2014 at 10:33. Reason: typo
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