Amiga 500 Floppy DF0 / DF1 Switchable mod - help.

big0z

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Hi All,

I cant seem to find the original post, on this forum, about being able to switch default floppy drive's channels.
Can some please show me which pins on the CIA EVEN chip are lifted and crossed ?
I have provied a picture of the chip - if someone could download it, and draw some lines, to show me the exact pins.

CIA_Even.jpg

Thanks for your help. (y)
 

-Acid-

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Does this mod make it so the internal drive is df0 and the first external drive would then be df1?
 

BLTCON0

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Does this mod make it so the internal drive is df0 and the first external drive would then be df1?

(Obviously you meant it the other way round)

The drives are indeed swapped but only at the selection level. The external drive will work fine as df0: but the internal will not work as df1: under trackdisk.device because there are no drive ID provisions on the motherboard (for DD drives, trackdisk.device requires an ID from df1: but not from df0:, so there's a funny situation: the external drive cage does have the ID mechanism but it's now redundant since the drive is addressed as df0:, while the internal one is inoperable since it's now addressed as df1: and lacks the required ID mechanism).
 

-Acid-

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Yes you know what I meant :)

I was thinking swap them over and then you could use an external floppy emulator as df0 and the internal as df1, but that idea is out the window now :(
 

BLTCON0

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Yes you know what I meant :)

I was thinking swap them over and then you could use an external floppy emulator as df0 and the internal as df1, but that idea is out the window now :(

It can be done but you need to re-implement an ID mechanism for the internal drive.
Flip your A500 board and on the underside solder an 1N4148 diode between Gary pin #46 and ODD CIA pin #7 (cathode ODD CIA side), do the same between EVEN CIA pin #13 and ODD CIA pin #7 (cathode ODD CIA side) then solder a 10 KOhm 1/4 watt resistor between ODD CIA pin #7 and GROUND. Watch out for short circuits (= insulate where needed).
That ought to do it.
If you ever install an HD drive internally, undo everything.
 

Arnie

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Interesting...So if you had a HD floppy drive then you could switch between DF0:, DF1: just by swapping pins 13 & 14, is that right?
 

BLTCON0

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Interesting...So if you had a HD floppy drive then you could switch between DF0:, DF1: just by swapping pins 13 & 14, is that right?


Yes (it's the very reason on the A2000/A3000/A4000 you need to actually remove the "DF1: enable" jumper to get an HD drive working as such. All the jumper does when set is pass-through a DD-fixed ID, so the system can "detect" an ID-less installed DD drive.
With the jumper removed the DD-ID is blocked, which serves equally well both the 'no drive' scenario (as no ID will be reported) and the "HD drive scenario" (as the drive handles ID report itself, sending either HD or DD IDs depending on disk type inserted).
 

Adry82

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Yes you know what I meant :)

I was thinking swap them over and then you could use an external floppy emulator as df0 and the internal as df1, but that idea is out the window now :(

It can be done but you need to re-implement an ID mechanism for the internal drive.
Flip your A500 board and on the underside solder an 1N4148 diode between Gary pin #46 and ODD CIA pin #7 (cathode ODD CIA side), do the same between EVEN CIA pin #13 and ODD CIA pin #7 (cathode ODD CIA side) then solder a 10 KOhm 1/4 watt resistor between ODD CIA pin #7 and GROUND. Watch out for short circuits (= insulate where needed).
That ought to do it.
If you ever install an HD drive internally, undo everything.

hi i am new and i talk a bad english sorry :D
im doing an amiga 500 case with df0 Floppy pc (with hack 1.44) and df1 gotek with an external floppy electronic, if i do this swap (13/14) my df1 come a df0 and ok but my df0 (floppy pc 1,44) come a df1 or not?
sorry for my bad english i hope you can help me.

there is a scheme for do this swap with pass to pass photos?
thank you
 
Last edited:

Adry82

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Perfect , swap done ... and work fine , but my df0 don't work as df1, can i have a scheme for do it ? or i need use one more external floppy logic?
 
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