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DavidMil

Bare 850 Printed Circuit Board.

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Found this, so I thought I'd share. Seems like I remember someone asking about an image of a bare 850 board...

 

DavidMil

 

 

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I've always been interested in how the 850 works. I built loopback testers for the four serial ports. Believe it or not,

you can not use one loopback tester for all four ports. And I wrote a basic program to test the four ports. I've been

working (well, not for a long time) on a device that will test the parallel port, but haven't got it perfected to my satisfaction

yet.

 

DavidMil

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Wow great link. Nice that there's assembly instructions too, would be fun to assemble one from scratch. I even have blank 2532 eprom's and learned how to program them if anyone needs.

 

There's enough retro adapters out nowadays, maybe I can find one that allows a 2732 to work with a stock config 850 pcb.

 

Speaking of which, I'm curious to collect the various 850 ROM versions, I've read there were at least 2 or 3? I have 2 850's I plan to dump their ROMs.

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Wow great link. Nice that there's assembly instructions too, would be fun to assemble one from scratch. I even have blank 2532 eprom's and learned how to program them if anyone needs.

 

There's enough retro adapters out nowadays, maybe I can find one that allows a 2732 to work with a stock config 850 pcb.

 

Speaking of which, I'm curious to collect the various 850 ROM versions, I've read there were at least 2 or 3? I have 2 850's I plan to dump their ROMs.

 

As far as I know there were three rev levels. I'm guessing that the first rev level was just marked as C012099. Rev two and three have C012099-2, and

C012099-3 respectively (this info is from my 850 Filed Service Manual). I'm thinking about building one from scratch since I found a PCB. I've got all the

parts except the 4K ROM. I'm going to call Best and see if Brad has any left. If not, Nezgar, can I send you my rev 3 ROM, and could you burn me a copy?

 

Thanks,

DavidMil

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Looking closely at that PCB, I'm wondering if it might have been a reject as some of the parts are actually hanging off the edge (at least according

to the silk screen. Click on the top side picture and look along the break away at the silk screen for A109...

 

David

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As far as I know there were three rev levels. I'm guessing that the first rev level was just marked as C012099. Rev two and three have C012099-2, and

C012099-3 respectively (this info is from my 850 Filed Service Manual). I'm thinking about building one from scratch since I found a PCB. I've got all the

parts except the 4K ROM. I'm going to call Best and see if Brad has any left. If not, Nezgar, can I send you my rev 3 ROM, and could you burn me a copy?

 

Interesting, I'll see what's in my 850's. If its the same 2332 type mask ROM like the 1050, I found you can just swap the ROM into an Atari 8K cartridge that uses 2 4K chips like like BASIC and dump it with a DOS "save memory" command. It will be in one of the upper or lower halves (or both) of $A000-$BFFF.

 

Looking closely at that PCB, I'm wondering if it might have been a reject as some of the parts are actually hanging off the edge (at least according

to the silk screen. Click on the top side picture and look along the break away at the silk screen for A109...

 

Yes interesting the silkscreen box is off the edge, but the traces and thru-holes are all still intact, so should be perfectly usable... Hard to find a good picture of a populated board online, but it seems that the sockets are pretty much hanging off the edge here too:

 

img13.jpg

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If anyone needs any technical data on the 850, schematics, the source code to the 850 ROM, etc, its all up here:

 

http://www.atarimuseum.com/computers/8BITS/400800/peripherals/Communications/850/index.htm

 

Good stuff! Although, I'm not an assembly expert, but the source code appears to be for the R: handler that downloads to the computer -- not for the 850 ROM itself?

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Got a successful ROM dump from my 850!

First of all, What is this type of socket I see on my 850? Never seen it before, looks like some kind of system to help release the chip, but I cracked it a bit on extraction... Chip markings of "C012099B 185©1981 8233" don't immediately suggest a revision, but the date code indicates August 1982...

Used a "Video Easel" cart to swap the ROM into temporarily. Then boot DOS 2.5, Save Binary file: ROM850.ROM,A000,BFFF. I was initially really confused, as I kept getting error 165 when trying to use "850.ROM" as the filename... Took me a while to remember that DOS 2 doesn't like a number as the first character of a file name. Erg.

 

The ROM fills the upper portion of the 8K cartridge space. A000-AFFF was all FF's, and B000-BFFF had the 850 ROM content. Transferred it to the PC, and stripped the first 2054 bytes to land at the final raw 4096 bytes from the chip.

Then sadly, in my haste I fell for the ol chip orientation trick, as I did not take note of the orientation prior to extraction, and it was not immediately apparent to me which way the socket was keyed.. The bloody 6507 is reverse orientation of the ROM too.. Anyhow, i got it backwards, and probably blew the ROM when I went to test it... blarg

850 C012099B 185©1981 8233 CRC32 2CF990B9.ROM

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@Nezgar:

 

The ROM socket is likely a type of zero insertion force(ZIF) socket, pulling out the end piece would unlock the pins for easy IC insertion/extraction.

This one appears to be a low-profile version, most ZIF sockets are much taller.

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Got a successful ROM dump from my 850!

Then sadly, in my haste I fell for the ol chip orientation trick, as I did not take note of the orientation prior to extraction, and it was not immediately apparent to me which way the socket was keyed.. The bloody 6507 is reverse orientation of the ROM too.. Anyhow, i got it backwards, and probably blew the ROM when I went to test it... blarg

 

I can send you my rev 3 chip to look at and maybe make me a copy (which I'm willing to pay you for).

 

David

Edited by DavidMil

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The ROM socket is likely a type of zero insertion force(ZIF) socket, pulling out the end piece would unlock the pins for easy IC insertion/extraction.

This one appears to be a low-profile version, most ZIF sockets are much taller.

I thought that as well, but I'm just unfamiliar with how to 'operate' it... the 'lever' on the end doesn't seem to pull out or lift (didn't want to force it either), and the plastic is extremely brittle due to age, so I may end up just replacing the socket with a machine socket anyway.

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When I tried to remove my ROM chip, the clip shattered into three pieces. So like you I'll just replace the entire socket.

 

David

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Congrats to DavidMil, as he was also able to use the 8K cart trick to dump his 850 ROM, and we found the resulting code was the same as mine. His chips date code is actually a littler older, but I suspect the '-03' is just a plant/production run identifier similar to what I've seen on GTIA/ANTIC, etc rather than a revision identifier.

 

So, now we have two 850's verified mask ROM code with CRC32 2CF990B9.

C012099B-03 date code 8210 (March 1982) - DavidMil

C012099B date code 8233 (August 1982) - Nezgar

 

So, to satisfy my curiosity, it would be great to find additional dumps from earlier 850 ROM's to find the supposed earlier revisions. I think I might have been imagining I had two, so I only have the 1 to contribute for now.

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Hi Nezgar ---

 

Yes, I only had the Source Code to the 850 handler posted.

 

I just posted the Source Code to the 850 ROM and other sources as well, the Atari Museum 850 page has been updated.

Click on 850 ROM Source Code and download the ZIP. I think you and everyone else will be pleasantly surprised.

 

http://www.atarimuseum.com/computers/8BITS/400800/peripherals/Communications/850/index.htm

 

 

Curt

 

 

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Hi Nezgar ---

 

Yes, I only had the Source Code to the 850 handler posted.

 

I just posted the Source Code to the 850 ROM and other sources as well, the Atari Museum 850 page has been updated.

Click on 850 ROM Source Code and download the ZIP. I think you and everyone else will be pleasantly surprised.

 

http://www.atarimuseum.com/computers/8BITS/400800/peripherals/Communications/850/index.htm

 

 

Curt

 

 

Very nice group there. I wonder if revision notes exist somewhere else as well. It would be good to see the thinking behind the changes and what the changes were in the thoughts of the persons involved.

edit

It indeed was pleasing to wander through this, I haven't made it through the handler yet. this looks like it cover 1979-1980 so far I can't help but think some more it is hiding or lingering...

 

-This is of particular interest, as some fixes can be affected, and a better understanding of how the device is capable of exerting far more control than it has been given credit for. I'm still a great fan of the 850.... ;)

 

Now to get some dumps of the different revisions, this allows the best of all to be stitched together once again. It also gives greater access to folks wrestling with control over the 850. I still haven't tracked down the librarian of the users group that had the break down of what was different from revision to revision..

 

Thank you once again, You keep making me happy!

Edited by _The Doctor__

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Congrats to DavidMil, as he was also able to use the 8K cart trick to dump his 850 ROM, and we found the resulting code was the same as mine. His chips date code is actually a littler older, but I suspect the '-03' is just a plant/production run identifier similar to what I've seen on GTIA/ANTIC, etc rather than a revision identifier.

 

I think we went over this a couple of years ago.

Normally I would agree with you Nezgar, but Appendix 6 of the 850 Field service manual give info on software upgrades.

I've posted a pic of the page below. I tend to think that rev 3 was the last software upgrade that Atari did to the 850 as

chips with later manufacture dates didn't have any version listed.

 

DavidMil

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DavidMil, I'm not disagreeing with you - your C012099B-03 may very well be revision 3 as that document describes. That's interesting that's written that way though...

It's just that we now have hard evidence of another chip (mine) with part number "C012099B" without the "-03" that contains the same dumped code.

We need to find more original 850 ROMs to dump to with different code before we can tell for sure that there's a way to visually determine the version by chip markings..

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I have seen C012099B-2 and -3 and now yours without any rev level. Who can tell what went through the minds at Atari and their

contractors back then?

 

David

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Doing some reading of old threads, one of the ROM differences was the ability to automatically download the R: handler from the 850 more than once. Some units would require a power cycle for it to work again.

 

DavidMil, since my ROM is toast for now, can you test for this behaviour with your working ROM?

 

And then others can test for 850's that behave differently, meaning we have 1 easy behaviour to check for a different ROM without opening.

 

Can anyone remember any other functional 850 ROM differences?

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