[Coladam] Coladam Digest, Vol 81, Issue 12

John Turner gimechip at live.com
Fri Mar 16 18:41:44 CET 2012


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RESPONSE 1
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Rich,
Thanks for the reply. It shouldn't be too difficult to read the MI firmware if it is in a standard EPROM. It could be read and disassembled. However, I wouldn't disrespect Mark's copyright. If it is housed inside of a microcontroller of some sort, I have no doubt that it would probably be protected from reading. I protect my PLD/GAL etc. chips from reading, but only because every programmer that I have defaults to protection on and I'm just too lazy to uncheck the box :-) I usually make all of the files for my projects freely available anyway.

I've recently purchased four coleco 5.25" 160k drives from other collectors over the past couple of months. No two came from the same person. I wanted to have two Digital Data Drives and Two Floppy drives on each of my adam systems. Note, that as of this moment, I have yet to power a single one of them on (I have been busy finishing the design of the 512MB Ram upgrade for the Tandy Color Computer 3 - yes, I know - 512MegaBytes on an old 8-bit machine is ridiculous - but I just couldn't help myself. A story for another time... and a different list...)

Anyway, the fact that the Coleco Disk Drive is an Adamnet Device means that we could probably interface just about any storage medium to the Adam via Adamnet and have it respond to the disk ID's and as far as Adam would know, he would be talking to a disk drive.

I've had a quick look at the Adam Disk Drive schematics from Coleco as provided by Rich Drushel - the whole thing is basically a complete self contained computer system (similar, I suppose to the old Commodore 1541's). The CPU appears to be a 6803 rather than a 6801. I have yet to take apart one of my drives to verify this, but if this is indeed the case, the 6803 does Not have internal ROM and relies on an external ROM (or EPROM) - this would be a blessing of sorts as this would give me access to the operating system of the drive by simply reading the rom and disassembling it. The Disk In sensor appears to be nothing more than an optical sensor which is read at P10. It should be a simple matter to patch the original coleco code such that a check of P10 always returns true (disk in) thereby completely eliminating the need of the disk in sensor (or simply tying the logic level of P10 to indicate disk in always, which would require no code patching - only cutting the trace that connect the sensor to P10 and then running a jumper wire to P10 to tie it to the proper logic level). The drive also uses the WD2793 FDC chip. This is a nice old chip, but requires a few analog adjustments which can be a pain (trust me, I've had to do these adjustments on CoCo disk controllers - 3rd party ones that used the 2793 (these were all hobbyist built, as commercial CoCo controllers mostly used WD1793, WD1773, SY6581 and MB8877A FDC chips)). The advantage of this chip over the WD1773 (one of the most popular I suppose for CoCo controllers) is that it can support Hi-Density Data Rates. However, given that the 6803 in the Adam Drive runs at 1MHz, only 720K could likely be supported. The 6803 would need to run at 1.8MHz or better to properly handle Hi-Density (assuming software polling techniques are used - I'm not, at this point, certain how the drive operates, so I can't say for sure.) If I were to build a replacement Adam disk drive, I would probably use the WD1773. It is a 28 pin chip, with all data separator hardware, etc. built right into the chip and no analog adjustments needed. Plus, even though not officially supported, if you clock the WD1773 at 16MHz instead of the official 8MHz, it can do hi-density. Since this overclocks the 1773, what you would want to do would be to have it normally clocked at 8MHz, but when you went to read or write a sector, switch to 16MHz, perform the data operation and then immediately drop the clock back down. This would prolong the life of the chip (although I have yet to kill one operating it at 16Mhz). So, anyway, back to the schematic: I think it would be a relatively simple task to duplicate this drive controller, using a WD1773 as the FDC chip, eliminating the disk in sensor by one of the previously mentioned methods, and since any 5.25" drive you are likely to find is going to be double sided, it could be made to see side 1 of the disk as drive 1 and side 2 of the disk as drive 2. When using a format such as this each side of the disk seen as a separate drive, it is important to keep a single head control table rather than two head control tables as would be used with two separate drives. This is because whatever track head 0 is on, so is head 1 and if you are using two head control tables, the 6803 would think the heads were in different positions which would lead to randomly corrupted disks. This is an important point that is often overlooked in such designs. Anyway, all of this is based on quick observations and all of it may be completely WRONG. I have no practical experience with the Adam yet, a fact that I hope soon to rectify. I will probably give a go at creating a replacement controller and drive. Once I have disassembled the 6803 code, it should also be a simple matter to patch the code for 360K, 720K and 1.44Meg drives. I would probably also use a more modern microcontroller than the 6803. For that matter - since the microcontroller handles the FDC chip, there is no reason why a 37C65 or other FDC chip couldn't be used. Many possibilities exist and perhaps I'll come up with something soon. I make no promises other than this is something I'd like to have a go at.
> Message: 3
> Date: Thu, 15 Mar 2012 23:39:12 -0400
> From: Frances and/or Richard Clee <cleechez at tamcotec.com>
> Subject: Re: [Coladam] Introduction and Coleco Adam Floppy Disk Drive
> To: coladam at adamcon.org
> Message-ID: <4F62B5E0.9020104 at tamcotec.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> Hello John and welcome to our list. May I offer a history lesson, based 
> on appearances and a vast fund of ignorance.
> 
> Back in the day, very few Adam 5-1/4 drives were produced, with 
> apparently their own exclusive EPROMs keyed to the unique Adam operating 
> system. These were single sided 160K units produced and assembled for 
> Coleco by some Oriental outfit I don't recall. The controller board was 
> poorly designed and prone to overheating, and a disc-in-place sensor was 
> mandatory.
> 
> When Mark Gordon founded Micro Innovations and began producing Adam 
> double-sided 5-1/4" discs, he bought generic double-sided 360K discs and 
> mounted them on a board with firmware of his own design. A number of our 
> developers have tried reading Mark's firmware but if there have been any 
> successes they have not been publicized. Mark did copyright his work and 
> the copyright is still alive.
> 
> My guess is that it was easier and cheaper to produce an upgraded 
> generic disc drive than to try to replicate the Adam original.
> 
> But beyond that, I'll leave it to those who know what they are talking 
> about to fill you in. - rich c
> 
> 
> 
> 
> 
> 
> On 3/15/2012 7:46 PM, John Turner wrote:
> >
> > Hello. My name is John a.k.a. Big John because my son is Little John. I am a vintage hardware developer who primarily works with the Tandy Radio Shack TRS-80 Color Computer series. I have recently acquired (at quite an expense unfortunately) much Coleco Adam equipment. I have to say, I love these machines.
> >
> > The reason that I have joined this list is that I am wondering if anyone has the EPROM or EPROM image required to convert an Adam Floppy Disk Drive (FDD) to 1.44Megs? Also, are the instructions posted anywhere online. I develop hardware that I need personally and then if others are interested, then I produce a small batch. Let me know if anyone knows where I can obtain the info and eprom required for the drive conversion - Thanks - Big John
> >   		 	   		
> > _______________________________________________
> > Coladam mailing list
> > Coladam at adamcon.org
> > http://adamcon.org/cgi-bin/mailman/listinfo/coladam
> >
> 
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RESPONSE 2
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That is entirely a coincidence - my son - we have always called him Little John since I am also John and so when he began developing stuff for the CoCo 3 and he got me interested in "chiming in", I used Big John so as not to be confused with my Son :-) Thanks for the welcome. I do not know why these Adam computers have such a bad rep (I've read lots of unflattering things about them) - I LOVE THESE THINGS - They were truly an engineering marvel at the time of their inception. If Coleco had taken their time and not rushed it, worked out the bugs (such as the EMP pulse that erases DDP's), they could have had a winner. I remember after the cabbage patch craze back in the day, and Coleco's stock had hit around $2 a share, I was wishing I had the money to buy up stock because I kept thinking the Adam would turn things around - it's a good thing I was broke back then, or I would have ended up bankrupt :-) Do any of you guys (and ladies) remember after Coleco dumped the Adam, a company Called American Design Components bought up a TON of Colecovision and Adam systems and components from Coleco. They had even brokered a deal to put the Adam back into production, I assume it would have been a debugged version, IF THERE WERE SUFFICIENT INTEREST. I watched their adverts with great interest (in Radio-Electronics magazine and others of the time) and subscribed to their mail order catalog, only to one day be greeted with the notice that there had not been sufficient interest for them to continue that venture. Surely some of you folks remember that, or am I alone here? If you can find various hobby electronics magazines of the time, you should be able to find their ads and the info relating to this story, especially in issues of Radio-Electronics and maybe Modern Electronics. I don't know about computer shopper - it was twice the size of a phone book back then and I loved reading it. I think ADC may still be in business but I cant be sure if this http://www.adccomp.com/ is them or not. Back in 1986 I bought an Lambda/Your Computer PC8300, 32K RAM Module and Color Video Board from them - sadly, that system was lost to the mists of time.
> Message: 4
> Date: Fri, 16 Mar 2012 00:58:19 -0500
> From: "Jim Notini" <jnoti2 at comcast.net>
> Subject: Re: [Coladam] Introduction and Coleco Adam Floppy Disk Drive
> To: "John Turner" <gimechip at live.com>,	<coladam at adamcon.org>
> Message-ID: <84AEE8FE2BD142618E59C0245E122A80 at HomePC>
> Content-Type: text/plain; format=flowed; charset="iso-8859-1";
> 	reply-type=original
> 
> Welcome aboard Big John and glad to have. It is funny that you would use the 
> name "Big John" as actually there was a gentleman that used that nickname 
> back in the glory days of ADAM Users Groups/Mail Orders who was one of the 
> most prolific developers of hardware for use with the ADAM after Coleco 
> abandoned it. His name was John Lingrel and his company name was Orphanware 
> Business Systems, which later became C.L. Digital when he partnered with 
> another longtime ADAMite, Ron Collins. As I stated, he developed many 
> hardware add-ons including Memory Expander, Parallel Interface, Serial 
> Interfaces, 80 Column Video Units, Voice Synthesizers, Clock Cards, etc.
> 
> Big John even developed ADAM Disk Drive upgrade kits that converted your 
> existing ADAM Disk Drive from 5 1/4" 160K to 5 1/4" 320K or even 3 1/2" 
> 720K. The only two people who might have any info on these (firmware and 
> instruction) would probably be Herman Mason or George Koczwara... hopefully 
> they will see this and respond.
> 
> Besides a few others on this Mailing List, the only other person that might 
> have all this information, up to a max size of 720K, would be Terry Fowler. 
> I'm sure he still has the firmware program, but you would have to burn this 
> to a Prom yourself. You can contact him at www.ecoleco.com
> 
> Good Luck and keep us informed of your progress as we still love hearing 
> about new 'warez being developed for our favorite computer even after all 
> these years... especially if it is an SD Drive solution.
> 
> Jim
> 
> 
> ----- Original Message ----- 
> From: "John Turner" <gimechip at live.com>
> To: <coladam at adamcon.org>
> Sent: Thursday, March 15, 2012 6:46 PM
> Subject: [Coladam] Introduction and Coleco Adam Floppy Disk Drive
> 
> 
> >
> > Hello. My name is John a.k.a. Big John because my son is Little John. I am 
> > a vintage hardware developer who primarily works with the Tandy Radio 
> > Shack TRS-80 Color Computer series. I have recently acquired (at quite an 
> > expense unfortunately) much Coleco Adam equipment. I have to say, I love 
> > these machines.
> >
> > The reason that I have joined this list is that I am wondering if anyone 
> > has the EPROM or EPROM image required to convert an Adam Floppy Disk Drive 
> > (FDD) to 1.44Megs? Also, are the instructions posted anywhere online. I 
> > develop hardware that I need personally and then if others are interested, 
> > then I produce a small batch. Let me know if anyone knows where I can 
> > obtain the info and eprom required for the drive conversion - Thanks - Big 
> > John
> >
> > _______________________________________________
> > Coladam mailing list
> > Coladam at adamcon.org
> > http://adamcon.org/cgi-bin/mailman/listinfo/coladam
> > 
> 
> 
> 
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END OF RESPONSE 2
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> 
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> Coladam at adamcon.org
> http://adamcon.org/cgi-bin/mailman/listinfo/coladam
> 
> 
> End of Coladam Digest, Vol 81, Issue 12
> ***************************************
 		 	   		  


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