A1000 CIAs and fitting a boot selector

Amiga_CDTV · 29 May 2019, 20:21

Hi.

I am doing a cleanup/recap/drive maintenance to my A1000. While there, I am hoping to install a DF0/DF1 selector (I found these a nice addition in my A500 with an exernal HxC drive). The internal drive in my A1000 is somewhat temperamental, not to mention very loud.

My A1000 is an early PAL unit with the daughterboard. In this board, which one of the CIA chips is the one controlling the floppies, ie. to which the selector would attach to? On my board they are marked U6N and U6P.

I have one more of these (https://www.ebay.co.uk/itm/283468629873) selectors which I used in my A500. If the correct CIA in A1000 is U6N (further from the 68000) it won't fit due to the daughterboard pins next to it. If it's the U6P it *might* fit there.

In case the selector linked above won't fit, I guess I'll just build "the traditional" switch with stacked sockets and a switch to swap the required lines. I would have prefered the linked one due to the described "protection" to the CIAs but I guess the bare-bones switch method will work too.

Jope · 29 May 2019, 20:42

U6N has the floppy functions.

http://www.devili.iki.fi/mirrors/4x4....org/a1000.zip

Amiga_CDTV · 08 July 2019, 16:38

Quote:

Originally Posted by Jope

U6N has the floppy functions.

And you were correct as usual

I just finished installing the mod; a traditional stacked-sockets -boot selector fitted there Ok, and I have a small switch mounted hidden inside the side-expansion opening where it can be operated from the outside.

jdryyz · 07 January 2021, 18:04

Hi!

You mention your PAL A1000 has the daughterboard. Should I expect to have the same experience installing the switcher in an NTSC A1000 then? These models all came with the daughterboard, I believe.

The eBay link below is no longer valid but I suspect you may have purchased this switcher:

https://sordan.ie/product/530/boot-s...el1-amiga-500/

Is that correct?

Also, one more question if you happen to know-- if my externally attached drive becomes DF0 and the internal is DF1, am I still able to daisy-chain another drive externally to get DF2?

Thanks.

Quote:

Originally Posted by Amiga_CDTV

Hi.

I am doing a cleanup/recap/drive maintenance to my A1000. While there, I am hoping to install a DF0/DF1 selector (I found these a nice addition in my A500 with an exernal HxC drive). The internal drive in my A1000 is somewhat temperamental, not to mention very loud.

My A1000 is an early PAL unit with the daughterboard. In this board, which one of the CIA chips is the one controlling the floppies, ie. to which the selector would attach to? On my board they are marked U6N and U6P.

I have one more of these (https://www.ebay.co.uk/itm/283468629873) selectors which I used in my A500. If the correct CIA in A1000 is U6N (further from the 68000) it won't fit due to the daughterboard pins next to it. If it's the U6P it *might* fit there.

In case the selector linked above won't fit, I guess I'll just build "the traditional" switch with stacked sockets and a switch to swap the required lines. I would have prefered the linked one due to the described "protection" to the CIAs but I guess the bare-bones switch method will work too.

r.cade · 07 January 2021, 19:21

Keep in mind, at least on my A1000, when the drives are "switched" the internal drive will not be detected at powerup as DF1 and will not be available. You have to power on with the drives "unswitched" until the hand comes up, then flip the switch. This is because the ROM looks for some other signal to detect there is a floppy drive installed and it doesn't respond properly if you just have the floppy ID lines switched.

Amiga_CDTV · 07 January 2021, 19:29

Hi there.

Being PAL or NTSC shouldn't make a different regarding the CIA chips, AFAIK.

The eBay link I had in my post was probably something very similar, perhaps more like this: https://www.ebay.co.uk/itm/Amiga-500...r/324279512777 (ie. it has more than just the sockets and a switch, marketed as a safer solution that just swapping the lines).

However I couldn't fit that kind of a selector into the machine due to space constraints (mostly in horizontal space), so I went with a traditional type of switcher (with just two sockets and a switch to toggle the floppy select lines). Meaning the end product was pretty much like this: https://circuit-board.de/forum/index...500-1000-2000/ which did fit inside the machine.

As mentioned by r.cade, when the external drive is switched to DF0, the internal drive is not available (as DF1), this seems to be a limitation of the switcher. I am not sure if the additional external drives keep working with the selector. Most switcher manuals say that one should not toggle when the machine is powered on, some people say it's Ok.

jdryyz · 07 January 2021, 20:56

Thank you both for the info!

jdryyz · 03 May 2021, 17:40

Just a follow-up on this.

I ended up going with this drive switcher from AmigaKit:

http://amigakit.amiga.store/floppy-d...l?currency=GBP

Although not listed as being A1000 compatible, it fits just fine. I suspect the slightly angled socket on top has a lot to do with the fitting (see attached photo). Most other PCB designs I have seen are wider.

When the switch is activated, my external drive is DF0. I also lose the internal drive. DF1: no longer exists. If I attach a second external drive, I do get DF2.

Is losing DF1: true for all switchers? The Sordan switcher seems to imply that you can still use it.

https://www.sordan.ie/product/530/bo...el1-amiga-500/

r.cade · 03 May 2021, 20:04

This is normal.

Drives are detected during early kickstart, and the internal drive will not be detected as DF1 during this time due to other signals that aren't rerouted.

For the drives to be switched and both available, switch it to "standard mode" (i.e. internal DF0 and external DF1) and then as soon as the insert workbench appears, flip the switch. Both drives will then work switched around as you describe.

jdryyz · 04 May 2021, 15:42

Interesting. So I should any expect *any* switcher to behave similarly in this regard (losing DF1)?

I do not think I will test switching while the computer is hot, though. I will be able to utilize two external drives for now.

Quote:

Originally Posted by r.cade

This is normal.

Drives are detected during early kickstart, and the internal drive will not be detected as DF1 during this time due to other signals that aren't rerouted.

For the drives to be switched and both available, switch it to "standard mode" (i.e. internal DF0 and external DF1) and then as soon as the insert workbench appears, flip the switch. Both drives will then work switched around as you describe.

r.cade · 04 May 2021, 15:45

The signal you are switching is only a CMOS level voltage for configuration, there is no real danger. With that said, mine is actually a 3-position switch, on-open-off...

29 May 2019, 20:21	#1
Amiga_CDTV Mind Walker Join Date: Oct 2013 Location: Helsinki, Finland Posts: 165	A1000 CIAs and fitting a boot selector Hi. I am doing a cleanup/recap/drive maintenance to my A1000. While there, I am hoping to install a DF0/DF1 selector (I found these a nice addition in my A500 with an exernal HxC drive). The internal drive in my A1000 is somewhat temperamental, not to mention very loud. My A1000 is an early PAL unit with the daughterboard. In this board, which one of the CIA chips is the one controlling the floppies, ie. to which the selector would attach to? On my board they are marked U6N and U6P. I have one more of these (https://www.ebay.co.uk/itm/283468629873) selectors which I used in my A500. If the correct CIA in A1000 is U6N (further from the 68000) it won't fit due to the daughterboard pins next to it. If it's the U6P it might fit there. In case the selector linked above won't fit, I guess I'll just build "the traditional" switch with stacked sockets and a switch to swap the required lines. I would have prefered the linked one due to the described "protection" to the CIAs but I guess the bare-bones switch method will work too.

03 May 2021, 17:40	#8
jdryyz Registered User Join Date: Jul 2014 Location: USA Posts: 139	Just a follow-up on this. I ended up going with this drive switcher from AmigaKit: http://amigakit.amiga.store/floppy-d...l?currency=GBP Although not listed as being A1000 compatible, it fits just fine. I suspect the slightly angled socket on top has a lot to do with the fitting (see attached photo). Most other PCB designs I have seen are wider. When the switch is activated, my external drive is DF0. I also lose the internal drive. DF1: no longer exists. If I attach a second external drive, I do get DF2. Is losing DF1: true for all switchers? The Sordan switcher seems to imply that you can still use it. https://www.sordan.ie/product/530/bo...el1-amiga-500/ Attached Thumbnails Last edited by jdryyz; 04 May 2021 at 15:46.

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29 May 2019, 20:42	#2
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,861	U6N has the floppy functions. http://www.devili.iki.fi/mirrors/4x4....org/a1000.zip

07 January 2021, 19:21	#5
r.cade Registered User Join Date: Aug 2006 Location: Augusta, Georgia, USA Posts: 548	Keep in mind, at least on my A1000, when the drives are "switched" the internal drive will not be detected at powerup as DF1 and will not be available. You have to power on with the drives "unswitched" until the hand comes up, then flip the switch. This is because the ROM looks for some other signal to detect there is a floppy drive installed and it doesn't respond properly if you just have the floppy ID lines switched.

07 January 2021, 19:29	#6
Amiga_CDTV Mind Walker Join Date: Oct 2013 Location: Helsinki, Finland Posts: 165	Hi there. Being PAL or NTSC shouldn't make a different regarding the CIA chips, AFAIK. The eBay link I had in my post was probably something very similar, perhaps more like this: https://www.ebay.co.uk/itm/Amiga-500...r/324279512777 (ie. it has more than just the sockets and a switch, marketed as a safer solution that just swapping the lines). However I couldn't fit that kind of a selector into the machine due to space constraints (mostly in horizontal space), so I went with a traditional type of switcher (with just two sockets and a switch to toggle the floppy select lines). Meaning the end product was pretty much like this: https://circuit-board.de/forum/index...500-1000-2000/ which did fit inside the machine. As mentioned by r.cade, when the external drive is switched to DF0, the internal drive is not available (as DF1), this seems to be a limitation of the switcher. I am not sure if the additional external drives keep working with the selector. Most switcher manuals say that one should not toggle when the machine is powered on, some people say it's Ok.

07 January 2021, 20:56	#7
jdryyz Registered User Join Date: Jul 2014 Location: USA Posts: 139	Thank you both for the info!

03 May 2021, 20:04	#9
r.cade Registered User Join Date: Aug 2006 Location: Augusta, Georgia, USA Posts: 548	This is normal. Drives are detected during early kickstart, and the internal drive will not be detected as DF1 during this time due to other signals that aren't rerouted. For the drives to be switched and both available, switch it to "standard mode" (i.e. internal DF0 and external DF1) and then as soon as the insert workbench appears, flip the switch. Both drives will then work switched around as you describe.

04 May 2021, 15:45	#11
r.cade Registered User Join Date: Aug 2006 Location: Augusta, Georgia, USA Posts: 548	The signal you are switching is only a CMOS level voltage for configuration, there is no real danger. With that said, mine is actually a 3-position switch, on-open-off...

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