Saturday, May 23, 2015

My collection

I talk to a particular friend of mine frequently, and he seems more fascinated by the number of computers I now own instead of what they actually do.  So I thought I would write down a quick summary of my hardware collection, so that the next time he asks how many computers I have, I can answer.


I started with Commodore both back in the day, and more recently when I picked up vintage computing.  In terms of expense, this is still my largest group.  In terms of computers, I have:
  • 1 C64C
  • 1"breadbox" C64
  • 1 C128 (my favorite computer out of all of them, though I'm really liking the CoCo - time will tell if the C128 hangs on to the top spot)
The two C64's were actually my original computers from back in the day.  One was mine, one was my Mother's, and when she passed I got both.  The C128 was my first vintage acquisition off of eBay, and I mainly got it because I was listening to the Retrobits podcast at the time and Earl Evans did a show on it where he stated it was his favorite computer.  So I purchased one and pretty quickly found that I shared his enthusiasm for it, even though I actually don't use it much anymore.

In terms of peripherals, both old and new, I have:
  • 2 1541 floppy drives (one non-functional, both from original collection)
  • 1 1571 floppy drive (purchased with C128)
  • 1 SDIEC (SD card drive for the C64/C128)
  • 1 1541 Ultimate II (SD card/USB reader and more - easily the best of all the new hardware upgrades I've purchased for any platform)
  • MPS802 dot-matrix printer (from original collection - actually went through the effort of buying a new printer ribbon for it, but haven't yet tested it)
  • Teknika MJ-10 monitor (from original collection - composite video works but chroma is off, use an LCD tv now instead)


I started reading a little bit about Atari computers but never actually used one until recently.  I did not have good luck with getting Atari computers, and I think that's why I actually don't use them that much, though I still have an interest in them.
  • 2 Atari 800's (both non-functional, first machines I picked up but neither worked)
  • 1 Atari 130xe (semi-functional - it generally works, but the Reset/Select/Option keys above the main keyboard do not work.  In fact, clearly someone has modified it because there are actually two keys labeled "Reset", replacing the Start key.  None of them work.  But the computer did boot and all the other keys worked.  This is the Atari computer I actually wanted to use, btw.  128k and I like the look of it better than any of the other models.)
  • 1 Atari 800xl (Works!  This was the last computer I got, but by the time I did my interest in Atari had waned somewhat because of my prior bad luck.)
My list of peripherals is very small:
  • Atari 410 (non-functioning, came with one of the non-functioning 800's - yeah, that was a bad purchase)
  • Lotharek's SIO2SD (SD card unit for Atari computers)


Although I really associate myself much more with Commodore computers, I go back a long way with Tandy computers.  The first computer I ever programmed on was a Color Computer 1, but it was my brother-in-law's computer, not mine, so I didn't actually do a whole lot with it.  But when I got to housesit for a weekend, I sat down with the "Getting Started With Color BASIC" book and went through it all.  It was my introduction to computers and programming.  A little later, I did a fair amount of programming and gaming on both a TRS-80 Model I and Model III, but neither were actually mine.
  • Tandy 102 Portable Computer
  • 32k Color Computer 1
  • 64k Color Computer 2
  • 512k Color Computer 3 (most recent acquisition)
  • Cassette drive with cable
  • CoCo SDC

Honorable mentions

What I list above are all the actual vintage computers I own, but there are some other computers that fall sort of into the vintage computing area.
  • Apple 1 Replica - A replica of the Apple 1 done by Briel Computers, I purchased the initial version (assembled) a long time ago.  When I first got it, I didn't know much about electronics and didn't actually get it running.  I could get it to work with the AT power supply I had.  Since picking up electronics more recently, I pulled it out and hooked up a 5v power supply that I built and was able to connect to it from a serial terminal on my Mac.
  • KimUno - An emulator of the Kim-1 that I purchased in kit form.  It was built with all modern components, of course, and was considerably smaller than an actual Kim-1, but it had the same button layout and used a hexadecimal display like the original.  It used an Atmel328P (the same chip that powers the Arduino Uno - thus the Uno in the name) to emulator the 6502.

So what am I missing?

I feel like the two biggest gaps in my collection right now are an Apple computer and a Z80/CP/M machine.  With the Commodore and Atari computers, I've obviously done a lot with the 6502, and I really like the chip, and I like those computers a lot as well.  But obviously Apple was really the biggest producer of 6502-based computers, and I would really like to play around with one.

As for the Z80 and CP/M, I'm pretty familiar with the 6502 and am learning the 6809 now with the Tandy CoCo computers, but I still don't know much about the 8080 or Z80.  I've done some assembly coding on more modern Intel cpu's, but nothing before the 386.  I'd be interested to see what the 8080 looks like and how the Z80 improved on that platform.  And with the Z80, I'd really like to explore the CP/M world.  I used CP/M only a little bit back in the day, but there's a lot of software for it, and since I'm not really a big gamer, it's an environment that I'd still find interesting.  Incidentally, I'm aware that my C128 does have a Z80 processor and is capable of running CP/M, and I've actually used it to do so.  But I'd still rather have a dedicated CP/M machine.

I'm also quite enthusiastic about the PDP-8 emulator that is being developed by the same guy who did the KimUno kit.  In addition to just emulating a PDP-8, it will have LED's and switches on the front panel to really give the feel of working with a basic PDP-8.  When that kit comes out in July, I intend to add it to my collection.

Wrapping it up

So there you have it.  I have 8 working computers, or 11 if you include the non/semi-functioning ones, with far too little space to actually set them all up.  I generally only have 1 or 2 out at a time, and the rest end up getting kind of stuffed into a closet.  I definitely need to organize them and probably will move some of them down to the garage (e.g., I don't need my CoCo 1 or 2 since I now have a 3).  But I don't see myself getting rid of any of them.

CoCo 3 and 512k of ram!

It's here, my brand-spanking-new (to me) Tandy Color Computer 3!  It came as a standard model, so it only had 128k, but as I mentioned in my previous post, I had also ordered a 512k ram upgrade.  Coincidentally, my memory upgrade (and 6309 cpu, more on that below) happened to come today as well.  So I turned on the CoCo3 long enough to test it (everything seems to work), then started to remove the top to install my 512k module.  
And that's where my first problem popped up.  The case is actually pretty easy to remove, just 5 screws on the bottom and the top pops right off.  Or at least it's supposed to.  You can't really see it in the picture to the right, but the white top of the case fits on the board around the keyboard.  Around the keyboard are four cylinders connected to the top but that hold the keyboard in place.  They're not screwed there, they just rest there.  But it appears that a prior owner spilled something like glue which caused the top by the Ctrl and Right Shift to stick to the keyboard itself.  Even worse, one of the cylinders I mentioned, the one to the lower left of the keyboard, was also stuck, so the top wouldn't come off.  I couldn't figure out any way to unstick it, so I finally ended up breaking it.  That's the hole in the picture to left.  On the picture just below, if you look closely near the lower left side of the keyboard, you can see the plastic riser that used to fill that hole.  I tried to remove it without damaging the top, but after quite a while of fruitless effort, just snapped it off.

With the top finally off, I moved on to installing the memory module.  That's the 512k module in the picture to the left, the blue triangular circuit board just above the keyboard.  It was a little nerve-wracking to install, because it required removing 4 IC's and cutting two capacitors.  It was the latter requirement that made me nervous, because if I cut the wrong capacitor, it wasn't going to be easy to fix.  Putting back in an IC is easy (assuming I wasn't clumsy enough to snap off a chip leg or anything, which thankfully I was not - this time), but replacing a capacitor is not such an easy task for me, especially these because they're actually pretty small.

But fortunately it went smoothly and the memory upgrade worked without a problem.  The machine booted up as normal and gave me its standard memory output in Disk BASIC.  Of course, since that's in the neighborhood of 22k, that's not really an indicator if all 512k is available, though obviously its a good sign.  The memory module did ship with a memory test program, but unfortunately it was on a 5.25" floppy disk, and I don't have a floppy drive for the CoCo.  I have my SDC, but that requires a disk image, and for some reason Cloud 9 didn't have it available for downloaded.  But thankfully a quick Google and I had the disk image.  A little amusingly, the program was written to use 80-column text mode, which turned out to be all but unreadable on my screen.  Fortunately, it was readable enough for me to confirm that it had found all 512k.

So the other upgrade I purchased was a 63x09E cpu to replace the 6809.  Unfortunately, once the top was off, I realized that the 6809 is soldered on the motherboard, not socketed, so I'll have to desolder the existing cpu.  Looking back at the Cloud 9 page, I do see where it clearly says that, but I must have missed that.  I'm reasonably confident that I can remove it, but after struggling with the case, I decided I wasn't in the mood to tackle the cpu.  In any case, I want to wait until I can get a socket since I'll want to use that instead of soldering the new cpu directly to the motherboard.

So with that, I put the top back on and now I have a nice CoCo 3 with 512k of ram.  I did notice that the Right Shift is a little finicky, but that's a minor problem at best.  It does work, but you just really need to press it firmly.  Not sure about the Ctrl or Alt keys yet.  I press them while in Disk BASIC and a @ and = show up.  I don't know if this is normal behavior, but that's what happens in MESS when I type those keys, so I assume so.

As you can see from the photo, the hole is still visible, though it's not too bad.  At least I won't have to wrestle with the case again, when I finally get up the energy to replace the cpu.

Wednesday, May 20, 2015

Ok, another new computer...

So I got another new computer, a Tandy Color Computer 3, the third and final in the Color Computer line.  I hadn't actually planned on getting one, mostly because they tend to be a bit expensive, but I found one reasonably cheap on eBay.  They're actually kind of difficult to find.  They don't show up on eBay that often.  (Note the photo is just one I snagged off the Internet; I haven't actually gotten my computer yet.)

This one was good because, as I said, it was relatively cheap (about $100), and the seller (who did have a high feedback score) said it had been tested and worked.  So I figured I had to scarf it up since such an opportunity wasn't necessarily going to come by again.

So how is the CoCo 3 better than 1 or 2?  Well, to be honest, I'm not 100% sure.  The CoCo3 does come with 128k ram, but as I discussed in a prior post, I'm unsure how to use that from BASIC.  It also comes with a better video device, so higher resolutions are available.  And, thankfully, it has a composite video output, so I can ditch the RF modulator.  With the CoCo 1/2, I was actually connecting via an RF modulator, which amusingly gave me the unexpected nostalgic experience of banging on the table or tv to improve the picture.  That's something I haven't had to do for decades, but I guess that's part of the point of these older machine, to re-experience the old.  But no matter how hard I hit the tv, the picture only got so good.  So I'm looking forward to using composite again.  It may not be as good as vga or hdmi, but it's worlds better than the antenna input.

So in anticipation of receiving a functioning CoCo 3 system, I also purchased a 512k ram upgrade and a 63x09E replacement cpu from Cloud 9.  The 512k ram's benefit is fairly obvious, since what is true today was also true back in the day - more ram is better.  But 512k ram seems to be kind of the standard now, or perhaps more precisely the minimum for most CoCo3 users.  There are several pieces of software that I'm aware of that require 512k (including a nice port of Donkey Kong).

The benefit of the 63x09E, however, may be less obvious.  It's a replacement cpu that can fit in the socket of the 6809 that's in the CoCo 3.  It apparently has two modes of operation.  The first is strict 6809 emulation, so it acts just like a 6809 for software that is looking for this - which I assume is most CoCo 3 software.  But in 6309 mode, it's apparently an enhanced 6809, with more instructions, registers, etc.  Apparently some CoCo 3 software will take advantage of this if available and will therefore run faster, but will still run fine on a 6809 system.  Since it was only $16, I decided to go ahead and grab it, especially since I was already getting the 512k ram module anyway.

So really looking forward to getting my new toys and seeing what I can do with it.  The peripherals I've already purchased for my CoCo's (the Edtasm++ cartridge, cassette player, DriveWire cable, and the SDC) should all work just fine in my CoCo 3, so I should be off and running when it gets here.

Friday, May 15, 2015

New CoCo...well, new to me

So got my new CoCo yesterday.  It's a 64k CoCo2 that I purchased on eBay for about $60, including shipping.  And I'm happy to report that after some testing, it seems to work completely.  The only thing I haven't tested yet is the cassette interface.  I also got 3 cartridges with it.  One of them, a personal information manager, works, but the other two do not.  The cartridges do not have labels, so I don't actually know what they are, but I didn't really care, so no big loss there.  I did confirm that both my Edtasm+ cartridge and, more importantly, CoCo SDC work.  And as far as I know, the CoCo1 and CoCo2 are pretty much interchangeable.  There's nothing that one can do that the other can't, so it really is a drop-in replacement.

So then why a new CoCo?  Well, first I got it pretty cheap, so there's that.  Also, this is known to be 64k.  My grey CoCo1 is either 32k or 64k, but because of the peculiarities of the CoCo platform, I'm not sure which.  I'm sure someone more knowledgeable about the Tandy Color Computer could figure it out pretty quickly, but there doesn't seem to be a real easy way to do so, at least not one that I'm aware of.  So at least with this CoCo I don't have to wonder.

The other reason is just the size.  Desktop space is at a premium for me, and the CoCo2 is substantially smaller than its predecessor.  When I'm not using it, it just slides back pretty easily and still leaves me with substantial desktop space to use.  This was much less the case with the grey CoCo.  The one downside?  The keyboard feels better on the CoCo2 but is much, much louder.  And I'm already a loud typist, even on the quietest keyboard.  I expect to get noise complaints from the neighbors with this one. ;-p

Monday, May 11, 2015


So I got a item for my CoCo: A CoCo SDC.  This is a nifty little cartridge that plugs into my computer that adds virtual disk capabilities.  Essentially it includes Disk Basic functionality, but instead of going to real floppy disks, it goes to disk images on the SD card.  I don't know a whole lot about it at the moment, but still it's pretty cool.

A little ironically I got an Edtasm+ cartridge at the same time.  The irony is that the cartridge form of Edtasm+ is specifically for cassettes.  I got this off of eBay because I kind of assumed that the SDC would take longer to arrive than it actually did.  I play with several different retro platforms and have ordered SD card readers for each, and they always take a few weeks.  This one, however, got here within just a few days - the same day, in fact, as the Edtasm+ cartridge.  So the cartridge is kind of pointless unless I just get a hankering to do some programming to cassette.  

And I might.  It's the only retro computer I have with a cassette, and I kind of want to use it - though certainly not as my main storage device.  I suspect that in the end whatever assembler programming I will be done either using a cross-assembler or disk-based Edtasm+ - or maybe another CoCo-based assembler.

Friday, May 8, 2015

The weirdness of 64k in the CoCo

Although I've been playing around with vintage computers for a while now, I'm very much new to both the Tandy Color Computer and the 6809 platform.  Now every system has its oddities, but I have to admit that the way the CoCo handles 64k is the oddest thing I've seen with any vintage computer.

Now my understanding (and please someone correct me if I'm wrong) is that the CoCo does not directly address all 64k of ram, but instead effectively has two banks of 32k.  I believe this comes from Tandy's decision to use non-functioning 64k chips in their early machine.  When I say "non-functioning", I don't mean the chip doesn't work at all, just that not all the ram works.  But if one of the 32k block works, then they put it in the machine as a 32k chip, and then just use a switch to tell the machine whether to use the upper or lower 32k block.

But as the CoCo's production run wore on and ram chips fell in price, they started putting fully functioning 64k chips in, but still only advertised them as 32k machines and still only made one bank immediately addressable.  So even if you have a 64k CoCo, it will actually appear at first glance that you have a 32k machine.  For example, the screen shot to the right is from XRoar, but it's setup as a 64k CoCo, not 32K as the 24871 free ram might suggest.

So how to tell if my machine is actually a functioning 64k CoCo?  Well, as far as I understand, there's no easy way to tell.  I could open the box and check out the chips inside, but even if it has 64k ram chips, that doesn't mean it's a fully-functioning 64k memory module.  I also can't access all 64k from BASIC, so can't do anything there.  The only way I'm aware of to check is to write an assembly program to do so, since assembly is the only the only way to access all 64k.  But at present, I know almost nothing about 6809 assembly and even less about the intricacies of the CoCo architecture.  So I guess that's a future project...

Still it just seems like such an odd architectural limitation of the CoCo platform.  My understanding is that the CoCo 1 & 2 are basically the same, so I'm assuming the same limitation applies to both.  I don't know about the CoCo 3, but I'm unlikely to ever get one so my interest is more academic than practical for that machine.

Thursday, May 7, 2015

CoCo Edtasm+

Having recently acquired a CoCo 1 with 32k of ram (though possibly 64k, not sure about that yet - the CoCo seems to have some odd quirks when it comes to ram) and with only a cassette recorder for storage, I decided to buy the cartridge version of Edtasm+.  I'm actually pretty happy as I found a relatively cheap cartridge on eBay, and I hope to have it by next week.  As I looked at Edtasm+, I found that it comes in both cartridge and disk form, but since I only have a cassette the choice was pretty simple.  The downside to it, though, is that based on what I read you can't really include files, so all your source has to be in one file.  This makes sense, since you don't have dynamic file access with a cassette like you do with a floppy drive, but it is limiting.  It also means that you can't really build a library of macros and procedures, which is very important for any serious assembly language programming.