Researching the TRS-80 Coco 1/2/3 repairs & upgrades and differences between them.

Again, it's riveting stuff this as I had no idea what form, shape or design the Tandy Co Co's went for in terms of expansion and peripheral boxes.

They are quite something to behold in their variation and, at times, bulk.

All I recall were the basic Tandy colour micros on the shelf or in the window of the same name store and me thinking... what strange beasts are these and then someone saying "They're a bit like a Dragon" but I knew next to nothing as they were rarely (if ever) covered in the mainstream UK computer mags - would you agree, guys?

I got the impression that anything you wanted for them would be, like the Atari, quite expensive and very much proprietary so kinda steered well away and never ever knew anyone who owned one so they remained... exotic beasts.

You are opening up new frontiers to many of us on here, Matt - thank you.

The specs, whilst not being amazing, are nevertheless interesting as I did not have a scooby do.

 

You are welcome. By the same token they were always strange beasts to me too, just like the Coleco Adam too. I saw commercials for the Adam back in the day, the TV stations were flooded with commercials for it after it was discontinued and they were liquidating, but of course the commercials made them a going concern and seem like they were popular and well supported. But at the time I wanted nothing to do with turbo tape drives, I wanted a disk drive, and I couldn't afford even the fire sale pricing because they only sold it as a system including the printer, and had too, since the PSU for everything was in the printer! So luckily I avoided a dead system, riddled with bugs and failures, with a VERY limited software library of it's own, and then the Colecovision's game library as they were compatible, but even the Colecovision has less than a 100 titles, similar to the 7800, Lynx and Jaguar libaries because of the video game crash of '83/84. So it remained mainly a strange beast and curiosity to me, but I want one now for that very reason.

I remember the TV stations being flooded with commercial with and without William Shatner too, for the VIC-20 not long after the C64 came out, and they were unloading overstock and like Coleco and the Adam, were acting as if it was the latest-greatest that would have software and support for years to come!

This was also true of the TRS-80 Coco's. Though I would rather have the Coco 3, but they sell for $500 like the 1200XL. In the Coco's case though, I was an avid Radio Shack shopper as a youngster, so I remember always seeing some model of the TRS-80 Coco on display, and it did catch my attention because it was being demonstrated to someone at the time and it had the mouse and GOS environment, and pretty much looked like an Atari ST or Amiga quality computer on the surface. But even though they were meant to be low-end models, they were still selling them for $100-200 more than The C64 or Atari XL/XE's. So I tended to ignore them and only the Coco 3 caught my eye when it was released, but by then I had made my choice with the 130XE and was building a system and library for it.

So the Coco's remained a strange beast and mystery to me as well. I never knew anyone who owned it or the ADAM. I didn't even know anyone who owned an Atari. my friends all had C64's or Vic-20's or Apple II's and one had an IBM PCjr! So again it was another 8-bit micro that I always wondered about, but was satisfied with my 130XE, and actually felt it far superior to most other 8-bits and was proud of the fact even if friends scoffed. They stopped scoffing when they saw the Atari in action, and soon wanted to play it all the time.

Of course as many of you know, I had been planning on a C64, and if time and space and money allowed, followed with an ADAM, or BBC micro, or TRS-80 Coco, and fate or destiny just seemed to step in and put Coco stuff in my lap. Honestly I'd still rather have a C64, but they are just to damned expensive anymore, even though there are 100 on sale on eBay at any given time! Just a couple years ago you could get one for sometimes less than $50! Of course this is true of many vintages systems today.

The Coco's don't have a huge software library either, it seems like just a couple hundred commercial/semi-commercial programs were published for it, and about a quarter to one third are 16K cartridges from Tandy itself. But, I have discovered that it, and the Dragon 32/64 can be modded to use the other's software, or at least hacked versions of the software. And I have to start looking into Dragon Software, as I might just decide it got better software released for it, maybe even more? I might just turn this puppy into a Dragon full-time. I might not have too though, it may be a plug-in module. I have to look into it more. In which case I can have the best of both worlds and 2 systems in one! And now that @Vyper68 is getting a dragon, we can compare notes maybe in this area and help each other out.

 

All very stimulating and illuminating, Matt, as my knowledge of systems such as the Colecovision/Adam and Coco is virtually nil so all these extra bits of flesh you keep adding to the bones is really interesting and yes of course you and Richie will be able to bridge your know how and growing expertise as you investigate potential software successes and perhaps even get your coco breathing fire...yet!

Exciting times, fellas.

Never better to be in to retro micro!

 

It will be good to compare notes on your CoCo with my Dragon. I don’t have a massive amount of software currently but some of the Dragon’s library is very good. The Battlezone clone ( Rommels Revenge ) is excellent and that is Tandy compatible. Design Design also released a game called Dark Star which is also very good. There are a couple of games called BackTrack and Eddie Steady Go! which are good and may be worth checking out.
As far as hardware goes I have built a cartridge port extender which allows a cartridge to be fitted internally while still allowing access to the cartridge port from outside. Handy if you have a 32KB RAM cartridge and want to use a disk drive. Talking of disk drives I have built myself a disk drive interface and have been using it with my Gotek drive this week, so it makes it easy to save programs as opposed tape. I have a CasDUINO that enables me to load .cas files from MSX and Dragon’s so I have access to the Dragon cassette library as the Dragon Archives have nearly all the tape software released.
Finally I picked up a cartridge for the Dragon called DeMON which is a machine code Monitor program which worked fine. I opened the case and popped out the 4K ROM and fitted an 8K EPROM will Dragon Data’s AllDream assembler/debug software. I am waiting on another 8K EPROM and that will enable me to burn the DaSM/DeMON combo. So I will have saved myself a fair amount of money compared to buying DaSM/DeMON on feeBay.
Last thing is now I have the replacement power board fitted I am overhauling my original Issue 4 power PCB replacing the capacitors and voltage regulators with modern replacements. So hopefully when finished it will be more stable and reliable.

 

I haven't even loaded a program to my Coco 2 yet, though I have a cassette player for it and have recorded a couple of .wav files. In the spurts of free time that I've had over the past couple of months, I've only been doing upgrades to my Coco 2, and my 7800, and my 800, sort of rotating between them. Currently I'm in the middle of an S-video and audio out mod on my Coco 2 and one for my 7800 as well.

The Coco 2 mod I am going by somebody else's schematics and on the 7800 it's a combination of a couple different mods schematics by others and some of my own design where I felt I could improve over other's. And of course the 800, while mostly done mod and upgrade-wise, is undergoing the face-lift and make-over. A the moment I actually don't have any of my 8-bit systems up and running, all are in need of repair and/or in the middle of upgrades. Of course winter is approaching fast and I should have much more free time to see these projects and several other finished finally.

Though I mentioned them above in posts, here is what I've done to my TRS-80 Coco 2 thus far in list form:

-upgraded internal ram from 16 to 64K.
-upgraded OS with adapter board for larger pin eprom and added MS extended Basic
-upgraded Motorola HMOS 6809 MPU to newer, compatible Hitachi CMOS 63x09E MPU used in Coco 3's with the 1.78Mhz turbo mode and extended features.
-replaced all 74LS series IC's with newer 74HC or 74F series
-removed old RF box/board and am upgrading video with replacement video board
-upgraded the MC6847 VDG to the newer MC6847TI with lower case characters and true descenders.

I want to get the MOOH board as it has all the other upgrades I want to do included on it, but I may have to settle for the SDC board and do the 512K ram and OS-9 upgrades myself. I want to buy an original multi-pack device to plug in several modules at once, but I may have to build my own board and case for that as well as originals are expensive and rare and only a 2-port multi-pak is still available from home-brew dealers and I want at least a 4-port if not 6-port.

Once the video board upgrade is finished I will start investigating the TRS-80 tape and cartridge software library as well as the Dragon's and look more into what needs to be done for Dragon/Coco cross-compatibility.

Here is a link to hardware upgrades that are compatible with both Coco's and Dragon's.

https://thezippsterzone.com/hardware/

 

Have you looked at the CoCo VGA @M.D.Baker ? I have put my name down on the waiting list for one as they fit Dragons as well.
There is a PAL CoCo2 on eBay right now that I’m watching which hopefully I will be able to pick up for a reasonable price, as well as bidding on a very sorry looking Dragon 32 so I’m full on 6809 right now The CoCo is a 16KB model but there is no indication if it has been updated to 64K. So it will be interesting to see if I get it. The Dragon is a really sorry looking loft find so it might be a good candidate for the D.I.Y 64KB upgrade if I’m successful. I know Dave expressed an interest in getting a Dragon, it might need a new power board so it can use a standard 12V PSU.

 

Yes, I'm aware of the VGA board. I decided against it myself because I think I will be perfectly satisfied with the quality of video outs I make along with the external video-to-VGA adapter/upscaler that I already have and use for all my video/S-video equipment, and in fact, I suspect works better as it does with other similar devices I've tried and would rather use an external font/character board where the VGA board rests.

External font/character board:




And that VGA board is ultimately no different than my external VGA adapter (except maybe works with color artifacting) but my external adapter has more advanced features for a better picture:
http://www.ambery.com/dvh4.html

 

Well if I go ahead and get one for my little Welsh wonder Matt, we can compare and discuss

By the way I heard from Tormod about the 32KB upgrade and uDrive a couple of days ago so he is still active. Have you heard anything from him?

Loosing the bid on the Dragon so going all in on the CoCo2 now.

 

I just checked my emails again and no, no response from him yet. I sent one about a month and a half ago and another about a week ago.

Good luck on the Coco. Mine was only 16K without extended basic rom, I had dram on hand to do the 64K upgrade and I needed a 28-pin adapter board I got from the Zipster site which came with the extended basic rom, so I didn't have to burn one.

 

@Vyper68 , now correct me if I am wrong, but you bought a Dragon 32 and so with the 32K board you'll have 64K like the Dragon 64?

 

It would give me 32KB of extra RAM accessible via Machine Code. The Dragon 64 has a slightly different ROM and an extra interface. So not a proper D64 but it would run OS9

 

I missed out on the Tandy CoCo2 ( it went for £122 ) so I picked up another Dragon 32 for £50 instead. It has an earlier serial number than the one I currently have, so I am hoping that (a) it works as it's the old untested chestnut but in this case I can see it's likely to be true as there is no PSU with it and (b) it is one of the earlier boards with the 8 half faulty 64K chips which you can swap with working 64K chips. That would be preferable that cutting and bypassing tracks on my current Dragon. Then I'll start saving for the CoCo VGA board.

 

I sent out another email to Tormod today, or yesterday. Anyway I did get a response this time, and he did say he had responded to my previous emails so it was an error on my end as to how I missed them.

He said he was working on a new batch of MOOH boards, interrupted by the holidays, but will be shipping them in January. So I've placed my order and am just awaiting a response as to if I can pay now, or need to wait until they are done. I want to pay now in case I forget to set aside money for it in January and end up being flat broke just for some reason just when he asks me to pay later.

I'm very happy though, as this board takes the place of the SDC board, plus extra ram and an SPI (replaces MPI controller) expansion header for other drives built in, which I think means I won't need a drive MPI controller pak for a disk drive or two. Though I need to find out exact differences between SPI and MPI, I may still need a DI special cable or adapter to connect MPI style disk drives to SPI. Plus 512K extended ram that I'd have had to buy another board on top of the SDC to have. The MOOH also has rom socket on-board for burning 64K eprom and using NitrOS-9 which is an updated version of OS-9 for the Coco model 3, for handling the extra memory. Or another new multi-platform OS called Fuzix based on UNIX. So my Coco 2 will have it's original OS and I can have two other ones that use the extra memory and make programs for the Coco 3 (only the ones that don't use the 3's new graphic modes, so no games)work and Unix based programs.

I'll probably 3D print my own case for it, there's probably a print for one I can download made by someone else, whether unique or a clone of a program pak case anyway.

From the site:



The MOOH is a cartridge board for the Dragon and CoCo 1/2 featuring:

• 512 KB RAM, handled by a DAT (dynamic address translator) mostly software compatible with the DAT in the Tandy CoCo 3
• SPI interface with 4 slaves, one connected to the micro-SD card slot
• ROM socket for 27C512 type EPROMs (64KB)

The board is designed to allow Dragon and CoCo 1/2 computers to run multitasking operating system such as NitrOS-9 Level-2 and FUZIX, offering virtual address spaces for each process, as well as fast mass storage on SD cards. Other SPI devices can also be connected. The ROM socket acts like a standard cartridge ROM, additionally offering software selection of multiple ROM images. A boot ROM allows the MOOH to be used without the need for any other storage devices or MPI. The "SDBOOT" ROM loads a program or operating system from the SD card on power-on.

• Plugs into the cartridge port - without modification of the computer
• Dimensions 99 x 96 mm (fits inside FD-502 and CoCoSDC enclosures)
• Uses standard micro-SD cards

The board comes with a printed manual with programming details, schematics and internal logic code.


It would have ended up costing me more for the SDC and these other upgrades separately. The MOOH is probably the last upgrade I will need to do to my Coco 2, since I did all the other possible ones that don't require a separate board; newer, better CPU, 64K ram, better OS and Basic, video output upgrade, newer VDC chip with lower case text, and something else I replaced...but forget atm...I can't think of any other purchasable upgrades I'd want, except for a Multi-pak expansion so more things can be plugged in at once. But since the only modern alternative currently is a two-slot model, I think I'll just pay the premium eventually for an original 4 slot Tandy/RadioShack multi-pak with a case that matches my system.

So once I get the MOOH board, it's just software and original era peripherals I'll start collecting, just a disk drive and a couple expansion boards like Orchastra-90 or modern alternative, mainly. I'll have to look through all the first and third party peripherals and expansions to see what was and is available. But probably no more internal upgrades to the computer...well, I may eventually upgrade the keyboard if a reasonably priced one turns up, but since I don't plan on using this computer for a lot of typing, I think the "melted" keyboard I have will be fine. It's at least as good as the XE keyboard I lived with for 20 years...

MOOH page: http://tormod.me/mooh.html

 

Something else new and interesting I discovered for Dragon and Coco computers on eBay today, and then I did a search for more info on them. But basically an upgrade board giving the Dragon and Coco computers the advanced graphic capabilities of MSX 2+ machines! (much more advanced than original MSX computers or anything 8-bit including stock Atari graphics*) I may get one of these too, though it doesn't make them compatible with MSX software...so I'll look into it more...they do show a few screen shots of games apparently made for it already, on the site below.

The SuperSprite FM+ 6x09 (for either Motorola 6809 or the newer, faster 6309 by Toshiba?-which I already upgraded too) for Dragon and Coco 1/2 computers. It can be purchased in kit of built forms.



Even without a multi-pak device I can use this with the MOOH since this board has a pass-thru connector! But I'll wait until I have the MOOH first and look into the possibility of buying this next year.


https://www.dragonplus-electronics.co.uk/product/supersprite-fm-6x09-for-dragon-and-coco-computers/

Compared to Dragon and Coco, MSX and C64 and all other 8-bit stock computers graphics besides the MSX 2+, Atari 8-bit graphics are still more advanced overall, IMHO, but then I don't put nearly the stock others do in the number of sprites an 8-bit machine can display at once, and I know both the MSX and C64 have more than the Atari. But the number of graphic modes (bitmap and character), 16 times larger palette, ability to mix modes and far more colors on screen as a result, and faster non-sprite graphic abilities, like 3D and 2D scaling and smooth horizontal and vertical scrolling of the Atari put it head and shoulders above all other 8-bit computers IMHO.

Keep your sprites if that's what you like, to me it's just one small aspect of graphic capabilities, especially with Atari graphics. Besides, the Atari has enough P/M's (4 8x240 and 4 2x240 or 4 8x240 and 2 4x240 or 4 8x240 and1 2x240 and 1 6x240 or 5 8x240 or combinations to create multi-color sprites) if multi-plexing is used and changing the display list, with nearly double the speed processing of the MSX and C64, it can hold it's own then.

And no matter what the Atari 8-bit always has the advantage of "sprites" 240 pixels tall that allow many interesting things to be accomplished in games or for masking purposes, more colors on-screen, etc. So if one thinks about it the Atari's P/M graphics are more versatile, can be massively larger vertically and nearly "free" multi-plexing abilities with the use of DLI's alone, without a multi-plexing engine, even though there are less P/M's, aren't they still more advanced than C64 and MSX sprites? I believe so, at least in versatility if not amount.

Sorry, being artistically inclined and an eye for graphics, I tend to be a bit zealous about what I think is important in graphics and sprites aren't, except in one of the versatile uses the Atari can use them for; more colors on the screen like with Rastaconverter images and high-res multi-color using P/M's for more colors on screen. And that's also what makes me excited about the possibility of MSX 2+ quality graphics on my Coco 2!

*This is an Atari VBXE or Apple IIGS quality (actually I think this board and the VBXE are much more advanced graphically that the IIGS, but for sake of argument...)upgrade for the Dragon and Coco computers!

 

Actually, that's a scart port there that I thought was a pass-through, until I realized during close inspection that it's too short to fit an edge connector. That's the problem with only and overhead image...

 

Just an update on the Coco/Dragon cards I spoke of above (links in the posts)

I did finally get in contact with Tormod and he says he's making more MOOH boards now and they will be ready in January, so he's aware I want one including the SD card and boot rom. So I should have it in a couple of months.

Regarding the SuperSprite FM+ 6x09 board, I just ordered it, along with an adapter board for the 6309 that provides what I need to use with this board and access it's turbo 1.78MHZ mode without need of upgrading to the later revision SAM chip in my machine which I have been unable to find anywhere anyway.

Also, since the MPI multipak expansion units are so expensive (over $150 on average) and the newer versions made by enthusiast like the Mega mini multi-pak or the mini multi-pak sold out and no sign of more being made, I'm resorting to a Gerber file of an older (from the 90's I think) multi-pak build-it-yourself PCB and I'll get one ordered and made for me from PCBway or someplace then build it and print a case for it. However, in the mean time I also purchased a two-spot multi-pak device from the same place as the SuperSprite board, and though it's just a bare board it was only $25 and will at least allow me tho have the SuperSprite FM+ and MOOH plugged in at the same time. And since I probably won't be buying a disk drive or other peripherals soon with the MOOH's SD card, I probably only need the two spots for a while.

But I just spent over $200 with shipping on the SuperSprite board and the extras for a computer I bought for $50...so I'm all in now, and with all the immediate upgrading and modding I've been doing I still haven't run a single program on it yet or played a game. But it will have all the top and latest upgrades opening up a lot more software and OS's for me to use when I do get around to it. And especially all the software that's starting to come out for the SuperSprite FM+ which is similar in many ways to the Atari's VBXE giving it graphic abilities that even far exceed the Amiga and and ST's and I think really more comparable with Atari Falcon graphics with these two boards. Apple IIGS eat your heart out!

 

I was thinking of getting a Super Sprite FM+ for my Dragon but still pondering it. I have a 6309 already so I’m good to go on that front.

 

I think it's going to be good. I'm hoping that eventually there will be some drivers for it that will be able to emulate Coco 3 graphics (since SSFM+ graphics are better)and in conjunction with the MOOH able to run TurbOS-9, be able to run Coco 3 software, as well as getting it's own homebrew software of course. Remember, it also has a SCART output that the video can still be sent through the FM+ from the standard OS when in that mode, so it's another better video out option if, like me, you want to keep the VDG socket available for an exterior character set and font board. The VGA board does to an extent with it's new VGA modes, but nothing compared to the SS FM+.

Another thing I'm learning is that although I don't care much for most Coco peripherals going through it's cart/MPI port, especially when they are dumb devices that require these large controller boards plugged into the side of the machine to work, the stuff that Atari smart peripherals have built-in to them. And I prefer Atari's SIO and Commodores serial ports for standard peripherals.

But, I am learning that the Coco's (I assume the Dragons have the same port) serial "bit banger" port that a few peripherals like the cassette drive and some modems use, are very much like the Atari's controller ports, and both have PIA's controlling them and can be used for lots of different devices too, but it was easier and faster to use the MPI (just like the Atari with both it's SIO and PBI/ECI) so not used as much.

Yet Coco serial ports with PIA's controlling them, like Atari controller ports, are full of possibilities with I/O and communication interacting with other machines not made specifically for the system, like my project of using controller ports and Atarilab Interfaces for prototyping and research and stuff like taking control of a robot I want to build.

I upgraded to dual PIA's on my Atari to add more controller ports for this purpose, and the Coco/Dragon have dual PIA's built in from the start, but only one serial output they control. Yet the possibility is there to add more, and I could have the Coco and Atari networked through their PIA controlled ports very easily indeed!

I know that the other video upgrades like the VGA give you new modes too, but can you use those modes and character sets with legacy software? With the external (from the VDG, not the Coco/Dragon) character/font board it is made to work with the original graphic and text modes, they are compatible and you can run even legacy software in whatever new font you choose that the board comes with or you program to it.

That's part of my reasoning for choosing the External Character/font board and SSFM+ over a VGA board.

The reason I chose the MOOH over the Coco SDC was the extra features built into it too, beyond SD card disk emulation.

It just seems to me that the Dragon community are putting out better upgrades with more upgrades per board in combination, where the Coco community is making boards that do just one or two things, add just one or two new abilities to the Coco/Dragon and Dragon/Coco upgrades throw in a lot more and obviously with the SSFM+ are just pushing the envelope of the entire system and not just modern media and video solutions like Coco/Dragon devices.

The Dragon first, but Coco compatible upgrades are more like upgrades for the Atari 8-bit that include lots of features and really take the machines to beyond the next level, with full legacy compatibility still.

I'm definitely really liking the Coco computers for all the legacy and modern upgrades and add-ons and peripheral/media and controller/input device options they have available, just like the Atari 8-bit. I still have yet to see if I'll fall in love with it's processor, graphics, OS's, languages and software too.

But the combination of internal upgrades and external one through the MPI port really make me feel right at home on the hardware tinkering side, just like the Atari and it's internal upgrades and PBI/ECI and cart port upgrade options. That's one of the reasons I'd planned on getting a C64 first, because it's the same. I am including both first and third party gadgets available for these systems.

Oy, do I ramble on...one sentence from you and I write a term paper in response...sorry

 

Well, the MOOH board, as far as I know, is currently in production and I have one on pre-order. So I ended up getting the SuperSprite FM+ board first instead, along with a CPU pull-up board kit since I don't have the newer SAM chip, this takes care of the new addresses missing on the old SAM chip, that are required (along with 64K and extended OS, at least on the Coco) to use the new SS FM+ board. I also got their Oojiflip board kit, which allows two multi-pak's plugged in at once as an alternative to an MPI multi-I/O or new similar re-manufacture. All are available in kit or built form and the SS FM+ has a couple of options too, and can be bought in kit or built form. I went with the built SS FM+, since it's nearly the size of the Coco mobo and I have enough projects. But I went with kits on the others since they are small boards, to save a bit of money.

I've been doing some reflecting, after looking at the invoice, and questioning why I was so determined not to pay over $100 for another 8-bit computer, but am perfectly willing, without second thought, of paying more than $200 ($300 with other purchases for it) for an upgrade to that same computer...I've discovered some strange psychological tic in my thinking when spending money on this hobby... IIRC, the MOOH board will cost me over a $100 too!

 

well here we have my first attempt at 6809 assembler using the DASM/DEMON Cartridge. It should work on a CoCo2 if the Text screen starts at &H400 to &H600.

 

Pretty much 6502 with some funky extra label variations.

Does it have to have the @ to define it as a label?

 

DASM needs the “@“ to define labels. The other 6809 assembler doesn’t need that. It’s just a quick of the program.
I have been reading up on MAC65 this morning so I may try and convert it to the Atari.
Even though it is a very simple program to fill the screen with characters, the speed compared to a BASIC program is impressive. Now I know why games were written in machine code.

 

I rarely touch assembler these days, I did code in 6502 and used to PAL fix Snes PAL protected games in 65816. Learned a little 68000 to play with Copper lists on the Amiga but never got very far with that. Tried to write a game on the Atari and got a nice playfield and some totally random sprites on a fine scrolled left to right screen but when it came to an AI for the sprites I just went blank. My maths was never that great, so AI was just not a thing I could get a grip on.

I know, learning 6502 when your maths is not great, does not compute, but I enjoyed the tinkering..

 

I'm just going to be a Coco 2 user with some upgraded and advanced hardware for a while. Because I am already learning 6502 Assembly with Mac/65 and relearning Atari Basic XE, which I already have the books and languages for from the great Atari community and my own assets. a

And thanks to great people and support in the Bally Astrocade community, who have been excited about my restoration and now upgrade into a PC, have given me great deals and gifts on upgrades, languages and books as well, so I think co-learning 6502 and Z80 assembly and Atari Basic& AstroBasic is enough for now.

Once I get on solid footing with those machines then I'll start learning 6809/6309 assembly and of course Coco Basic is just Microsoft Basic and adapting to it by then after learning other Basics will be easy. Plus, if I do any real programming of games or apps on the 6502 and Z80, there are a lot more machines it can be ported to than with the 6809. Of course any small changes needed for Dragon compatibility will be included in the original program.

Unfortunately, I have not had the same great experience attempting to get involved in the TRS-80 Coco or Dragon communities and so no social encouragement either, like with the other machine's communities. Basically only @Vyper68 here has become a fellow traveler in 6809 land with our largely compatible machines.

 

So now we both have CoCo’s we can compare notes better Matt. It was cheaper getting a 64K CoCo than trying to buy a Dragon 64 and with Two Tandy joysticks all the manuals and 6 cartridges it was a steal. When you look out there’s a lot more support for the CoCo than the Dragon but then again the CoCo had a lot longer lifespan so it’s not a surprise.
The 6847 in my PAL CoCo is a 6847T1 like Matt’s so it has a proper zero,asterisk and lower case characters and because the MC1372 is on the main board the the composite mod was very simple. I plan a S-Video mod to improve the picture further when the cable arrives.
So now I can have a look at OS-9 …