High density floppy for the A1200

[Fabie]

Originally Posted by whitebird

And what about adding an HD compatible controller to the Amiga? The problem is that compatibility with Amiga disk formats would be lost if it's a standard PC controller.

So the best would be to build a custom controller from an FPGA for example, add Amiga capabilities like those of Paula and make it HD capable.

Anyone know where information about the Amiga FDD controller can be found?

that's an horrible idea...is something horrible like the catweasel for the Amiga
the best mod is create an original Amiga high density drive because it is a powerful device....slow but really powerful
The native high density drive can boot from floppy...read PC 1.44 floppies,copy protected software,create your own original Amiga disks etc
I think that the main reason that commodore never inserted them in the low-end models like the A600 or A1200 was because the HD drive well programed can copy lot of protected DD floppy without additional hardware
the high density device in bad hands like crackers and pirates and common ppl could did big damage

[Toni Wilen]

Originally Posted by pandy71

I can imagine - there is no need to create real hardware Paula emulation in software emulator.

There is always need if feature is used. MSBSYNC or 4us speed are not. (they are as unused as audio modulation features..)

Emulating features that no one has ever used is not worth the trouble.

So it was my question - difference between GCR and MFM mode from synchronization point of view

I guess there is no difference.

[pandy71]

Originally Posted by Toni Wilen

There is always need if feature is used. MSBSYNC or 4us speed are not.

Probably not for reading from file - there is no hardware for UAE that support direct reading from FDD.

Originally Posted by Toni Wilen

(they are as unused as audio modulation features..)

This one can be used to play in hardware 14 bit samples

Originally Posted by Toni Wilen

Emulating features that no one has ever used is not worth the trouble.

Agree - not important at all from software emulation point of view

Originally Posted by Toni Wilen

I guess there is no difference.

Difference not for software but for hardware for sure it must be... - it is like blitter (especially line mode) - non described mystery..

[orange]

Originally Posted by Fabie

The native high density drive can boot from floppy...read PC 1.44 floppies,copy protected software,create your own original Amiga disks etc
I think that the main reason that commodore never inserted them in the low-end models like the A600 or A1200 was because the HD drive well programed can copy lot of protected DD floppy without additional hardware
the high density device in bad hands like crackers and pirates and common ppl could did big damage

you mean to say any Amiga with 'native' HD drive can write back .ipf images of original games? no extra hardware needed? if so, i wonder why there isn't such program.

[Fabie]

Originally Posted by orange

you mean to say any Amiga with 'native' HD drive can write back .ipf images of original games? no extra hardware needed? if so, i wonder why there isn't such program.

yes....the high density drive can write back certain ipf files without additional hardware using the tool wwarp
I tried turrican 2 and turrican 3 and worked
other ipf files may need an extra device named SYBIL...a rare device that comes with the Emplant

[pandy71]

Sybil it is additional and programmable clock source for changing Amiga master clock - by connecting to the video port external clock source equal 8*Color Clock You can change speed for the whole system (audio, video, cpu and also FDD) - i personally clocked my Amiga up to the 32MHz then system halt (but it was ages ago) - changing this clock You can read and write FDD written by non-standard ie 125/250/500kbps speeds (like those 5 1/4 inch drives that they use 300kbps not 250kbps) - can imagine that Sybil can be replaced by programmable clock source for FD motor driver - then You can change rotational speed of disk without touching fdd bitrate (system clock remains not changed) - so Sybil is quite simple (PLL synthesizer - probably some VCO on NE564 with programmable divider or something similar - currently can be replaced by some NCO)

[whitebird]

It's interesting to see that some HD conversions uses only a PAL/GAL chip (like the Amtrade) and others uses more complex components (Actel A1010 FPGA) like the one from Power Computing XL Drive shown on this page:

http://eab.abime.net/showthread.php?t=43265&page=2

Generally you will not be able to fit more than 2 or 3 74LSXXXX chips in a PAL/GAL, but with the future of being able to electrically erase and reprogram the chip while in the design.

So converters built with GAL chips must work on a very simple basis.

It is written here:

http://www.amiga-resistance.info/bbo...280&artlang=de

that the SONY drive doesn't require any modification (no rewiring of the /DCD from 34 to 2).

In fact it's not completely true because redirection of /DCD from pin 34 to 2 is actually done, not by the GAL chip (because it's only a matter of passive rewiring) but directly by the PCB.

We can clearly see PIN 34 of drive going to pin 2 of amiga connector:

http://www.amiga-resistance.info/dow...d357_1_big.jpg

Then by following the tracks, /RDY signals certainly is generated by the GAL chip which also generates:

/INDEX: This signal is a short pulse generated once per disk revolution.
We can also see that the /RDY signal is fully generated by the interface.

Let's suppose the GAL chip works like a divider and halves the /INDEX frequency so that amiga sees only 150RPM but data will still be emitted at 500Kbps and that's not acceptable for the amiga. So there should be something else...

It's a pity we cannot see all the tracks, but with a bit of work, I think it would near be possible to reverse engineer the interface...