Sharing SIO devices between two Ataris

[adam242]

My two main machines are an 800 modded with a PAL ANTIC chip (runs nearly all PAL software correctly) and a 1200XL (for everything NTSC). I'd like to have them share a pair of disk drives as well as the desk...

 

Can I simply connect the two computers as the end points of the daisy chain, and only power one on at a time? Would this work without harming the other machine?

 

I'm handy with a soldering iron and comfortable doing mods and projects... If I were to build my own switchbox, how many of the 13 SIO pins actually need to be switched?

 

Lastly, is the Automatic two computer interface mentioned on Mathy's collection of special stuff still available (either assembled or as a build-it-yourself design) somewhere? The link on his page is dead, and I can't find mention of it anywhere else.

 

Thanks for any advice you may have....

 

 

Oh, and slightly different, but related: Has anyone successfully installed both PAL and NTSC ANTICs in an 8-bit with the ability to switch between them? That would solve my problem entirely, with one machine to run everything. There are a couple of years-old threads on the topic here, but no definitive answers.

[+David_P]

CSS used to see a switchable Quintopus that would let you do just that. There is some information on the CSS website. http://www.nleaudio.com/css/products/quintopus.htm

 

I also seem to recall a device from Supra called the Micronet, with about eight connections for computers, and one to the peripherals. Of course, if two users write the same sector at the same time, hilarity (and a trashed disk) will likely ensue.

 

See also this thread: http://atariage.com/forums/topic/135641-sio-hub/

[Bryan]

There are a couple problems with tying two computers together with SIO. The computer that is off will tend to pull down the lines. Plus, there's a power line in there that would need to be disconnected so you're not supplying power to the other computer. Since only a few lines are actually needed for most SIO peripherals (look at SIO2PC), you could probably put something like a 3PST switch at each end to isolate the computers from each other. The fancier way would be to use analog or bus switch components and have the computer's power enable them.

[Mathy]

Hey guys

 

Did you read the description of the automatic two computer interface Adam mentions at the beginning of this thread?

 

Sincerely

 

Mathy

Edited January 2, 2015 by Mathy

[gilsaluki]

Best Electronics APE Link, multiport device similar to Quintopus. Best still has them.

[adam242]

 

There are a couple problems with tying two computers together with SIO. The computer that is off will tend to pull down the lines. Plus, there's a power line in there that would need to be disconnected so you're not supplying power to the other computer. Since only a few lines are actually needed for most SIO peripherals (look at SIO2PC), you could probably put something like a 3PST switch at each end to isolate the computers from each other. The fancier way would be to use analog or bus switch components and have the computer's power enable them.

 

 

Thanks for the insights, Bryan.. I guess it's not as simple as leaving both A8s connected and one turned off. It does, however, look pretty easy to make my own switchbox. Judging by the lines used for an SIO2PC, I'm thinking switching the Data In, Data Out, and Command lines - pins 3,5,and 7 - and providing a common ground of course, should be sufficient for switching disk drives. A 3PDT switch should be all I really need.

 

Also, Bryan - you were one of the participants in the dual-ANTIC threads I dug up... do you remember any more details of how that might be accomplished? If I could pull that off in my Incognito 800, that would be the ONLY Atari I would ever need. 100% Compatibility.

 

Best Electronics APE Link, multiport device similar to Quintopus. Best still has them.

 

Found that one in their catalog... thanks for the tip, but it doesn't appear to be switchable. I don't think that's what I need.

 

@Mathy - Is that device (or a schematic for building one) still available somewhere? The link on your site is broken.

[Bryan]

Also, Bryan - you were one of the participants in the dual-ANTIC threads I dug up... do you remember any more details of how that might be accomplished? If I could pull that off in my Incognito 800, that would be the ONLY Atari I would ever need. 100% Compatibility.

 

 

A long time ago I looked into how many Antic pins would need to be switched. I think I got one Antic to sit in a mostly off-the-bus state so the other one would work without too much switching. I don't know where my notes went but I might look into it again. I think Nir Dary did some similar stuff too.

[thorfdbg]

Oh, and slightly different, but related: Has anyone successfully installed both PAL and NTSC ANTICs in an 8-bit with the ability to switch between them? That would solve my problem entirely, with one machine to run everything. There are a couple of years-old threads on the topic here, but no definitive answers.

It takes more than just swapping Antic to toggle between PAL and NTSC. The color carrier of the two standards is different, thus you also need to swap GTIA, and the PAL Atari's have a second oscillator that feeds GTIA with the color carrier frequency of 5/4th of the system clock.

[Mathy]

Hello Adam

 

I'm not sure if it's still available. I've emailed one of the guys who made the A2Ri, maybe he can tell us if he's still selling them.

 

Sincerely

 

Mathy

[Sikor]

Maybe this help something: http://atariki.krap.pl/index.php/Game_Link_II - use google translator from polish language

[adam242]

It takes more than just swapping Antic to toggle between PAL and NTSC. The color carrier of the two standards is different, thus you also need to swap GTIA, and the PAL Atari's have a second oscillator that feeds GTIA with the color carrier frequency of 5/4th of the system clock.

 

I understand that what I've done is not a true PAL conversion, but it suits my purposes just fine. I'm not looking to output a PAL signal. I just want the ability to run European software, and at the correct speed. Swapping ANTIC alone gives me 50hz frame rate and a longer VBLANK, which accomplishes this.

 

EDIT - I'm starting a new thread for the NTSC / PAL discussion... I'll keep this one for the SIO sharing topic!

Edited January 2, 2015 by adam242

[adam242]

Hello Adam

 

I'm not sure if it's still available. I've emailed one of the guys who made the A2Ri, maybe he can tell us if he's still selling them.

 

Sincerely

 

Mathy

 

Thank you! I'm sure I'm not the only person who would be interested in purchasing or building this device.

Edited January 2, 2015 by adam242

[adam242]

Maybe this help something: http://atariki.krap.pl/index.php/Game_Link_II - use google translator from polish language

 

That page appears to be empty?

[Sikor]

heh... Atariage phorum adding commentar after link. Try this: http://atariki.krap.pl/index.php/Game_Link_II

[+bob1200xl]

You can share I/O between two computers if you add a diode to the +5v line from each computer. You don't want to run +5v IN to the system that's powered off. I think the 800 will drive +12v out the SIO - leave that off.

 

Bob

 

 

 

My two main machines are an 800 modded with a PAL ANTIC chip (runs nearly all PAL software correctly) and a 1200XL (for everything NTSC). I'd like to have them share a pair of disk drives as well as the desk...

 

Can I simply connect the two computers as the end points of the daisy chain, and only power one on at a time? Would this work without harming the other machine?

 

I'm handy with a soldering iron and comfortable doing mods and projects... If I were to build my own switchbox, how many of the 13 SIO pins actually need to be switched?

 

Lastly, is the Automatic two computer interface mentioned on Mathy's collection of special stuff still available (either assembled or as a build-it-yourself design) somewhere? The link on his page is dead, and I can't find mention of it anywhere else.

 

Thanks for any advice you may have....

 

 

Oh, and slightly different, but related: Has anyone successfully installed both PAL and NTSC ANTICs in an 8-bit with the ability to switch between them? That would solve my problem entirely, with one machine to run everything. There are a couple of years-old threads on the topic here, but no definitive answers.

[Mathy]

Hello guys

 

The MultiLINK interface is based on/similar to the GameLink II interface. It's mostly used to load data from one computer to the next. IIRC, the first computer ("master") loads the data from disk. After that, the drive is disconnected and the game is loaded from "the master" into each computer ("slave") sequentially. I'm not sure if the Multilink/GL2 interface can be used to share peripherals between computers. The A2Ri would be ideal for that, but as the name says, it's 2 Atari's per A2Ri. And it has to be patched for the SIO2USB (not SIO2PC-via-USB!!!) to work.

 

Sincerely

 

Mathy

[Mathy]

Hello guys

 

Just heard from Thomas, the guy that developed the A2Ri. He sold 5 of them in 20 years. One of them to me. (And I really like the interface)

 

Sincerely

 

Mathy

[Mathy]

Hello guys

 

Thomas of the ABBUC-RAF has given me permission to publish the schematic, including silk screen, etc. You can find it here on my special stuff page.

 

Sincerely

 

Mathy

[BillC]

Looking at the schematic the A2RI uses a 74241 or 74HCT241 IC to switch/buffer COMMAND/READY/DATA-IN/DATA-OUT signals, plus some additional circuitry to operate the automatic switching.

 

I found the following posted 12 years ago about the Quintopus at http://comp.sys.atari.8bit.narkive.com/AmaGHcBa/sio-switch-box

 

With the Deluxe Quintopus, you can share the devices with 2 computers:

http://www.nleaudio.com/css/products/quintopus.htm

You could probably build something like this fairly easily and expand
the number of switched ports to as many as you need. On the one I have,
the switchs are DPDT toggles that appear to just switch in or out the
Motor Control (pin 8 and + 5 VDC/Ready (pin 10) of the SIO connection
for the devices on the switched ports.