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RetroChallenge 2015/07 (a.k.a. Summer)

To RetroChallenge or not to RetroChallenge, that is the question. As always it is doubtful that I'll have any time or energy to dig into a longer term project, but I consider this a way to motivate myself to get anything at all done, so under those conditions I can as well enter.

Some of the things I need to do is to replace the power supply in my BBC Micro, replace caps and install a CF card on an Amiga 600, fix some cables, play some PET games, take on some of the tasks I haven't finished in previous challenges and so on.

Process log - Latest progress

June 29, 11:00 (GMT+2)

Challenge set up.

July 1, 21:10 (GMT+2)

Starting off with something "simple", installing a CF drive into a borrowed Amiga 600. The original 40 MB HDD is fine, but due to installing a Vampire 4 MB internal memory expansion which clips onto the CPU, the IDE drive would no longer fit.

Unfortunately my 2.5" IDE cable is a bit on the short side, and has one pin blocked, so I had to carefully bend away that corresponding pin on the CF adapter card. I will also need an amount of isolation tape between the CF adapter and the memory expansion once I assemble it properly, to prevent any form of short circuit.

At first HDToolBox didn't seem to detect the card, so I had a look on the Internet for solutions, when I remembered that one needs to manually read drive parameters from the drive in order to use it. While the maximum partition size on the Amiga with FastFileSystem is 4 GB, it amazingly seems to have auto partitioned the 8 GB card into two 4 GB partitions.

Too bad the Workbench 3.0 boot disk I've used doesn't seem to have all the programs installed on it, so I haven't been able to format the CF drive yet, only partitioned it. Fortunately I have a fully fitted out Amiga 1200 with PCMCIA-CF and so on, so I'll be able to create the boot floppies required to install the system on the card, once I get to it.

July 1, 22:50 (GMT+2)

DUMBASS! Here I've got an Amiga 600 with 2.0 ROMs and Kickstart 37.350, which I'm booting with a Workbench 3.0 disk. It is amazing it actually boots, and not so strange that applications like SYS:Format fail, since I'm trying to run a program written for a newer OS version than the one in the computer!

Oh well, it means I should download install floppies for WB 2.04, 2.05 or possibly 2.1 and use, then I'll probably be able to install the system as well. Actually all the time I was thinking Amiga 1200 but this is a 600.

July 1, 23:55 (GMT+2)

After a failed Google search that only yielded me a strange downloadable Windows executable that I refused to open, I realized a friend of mine got a FTP site with all sorts of files, which is also where I found a good set of floppy disk images. After sacrificing some chess game, I now have the full set of install media, and the format command is almost 1% done when it comes to formatting a 4 GB partition... guess this one would have to run all night to finish.

Besides putting everything into place and eventually replace the caps for the somewhat malfunctioning sound, I also need to troubleshoot why the Return key doesn't register when all others do. I already tried to reseat the ribbon cable, I suppose the fault might be more complex.

I also need to do something pretty about the make-shift power supply, which is the same unit as I was playing with in 2012 but now placed in a clear plastic container and mains wires running on the outside of that one.

July 2, 08:30 (GMT+2)

Gah.. all night was not long enough. I had to leave for work with about 1.5 hours left to go so I had to cancel the process running all night.

Last time when I formatted a 2 GB HDD it took about an hour, but perhaps addressing the CF memory is slower. Actually I might repartition the card into smaller chunks, although I don't know how many partitions on a single drive are supported in Amiga OS, probably CFD0 - CFD9 or whatever the device is called.

July 2, 20:10 (GMT+2)

I repartitioned the drive into three: 1 GB system, 3 GB work and 3 GB games/spare. Then I ran the script supplied on the 2.0Install disk, and it would format the first two partitions in a few seconds. The whole system install process took about a half hour including a sandwich break.

It made me curious what is the difference, and found that the FormatHD script formats default named partitions with the quick parameter, which reduces format time from 8 hours to perhaps 15 seconds! :-O Now I understand there may be situations where it is not applicable, but I could have saved several hours through life if I had known before!

July 2, 23:25 (GMT+2)

My next goal with this computer was to install a Compact Flash to PCMCIA adapter, as well as the FAT95 file system so I can transfer files directly from a PC.

The installation of FAT95 is rather automatic and straightforward, just click on the icon. The biggest part is to get the L:fat95 file in its position. To install the compactflash.device, you should copy the file to the DEVS: folder and double click on the DOS driver for CF0, but when using Kickstart 2.05 on an Amiga 600, the latter causes a Guru meditation. This older version of the OS uses a file called Mountlist, also in DEVS: which I needed to edit manually. Fortunately the syntax seems to be the same as for newer DOS drivers.

Finally you need to MOUNT the new device CF0 which can be done in the S:Startup-Sequence, but even after doing that, the CF device icon doesn't appear in Workbench until I start a CLI and manually try to access CF0: upon which at first I get an error message, but on second attempt it can be reached and the icon shows up on Workbench.

Note that with Kickstart 2.1 or newer (Amiga 1200 has KS3.0 and upwards), the process is much simpler as the DOS driver supplied with the installation will work right away. I found a lot of discussion threads about this, but none was entirely clear, and just about everybody assume that you use an Amiga with PCMCIA slot, it is an Amiga 1200 - the remaining 600 users seem so few that they're forgotten.

July 3, 23:35 (GMT+2)

Not much to report. I got home after a hot day at work, and was too tired to do anything on the retro front. Well, except for assessing the damage caused by a short circuit from the power supply late last night.

It turns out the Amiga 600 seemingly was unharmed, while my 14" TV got some minor fault, perhaps with ground. It manifests as sound from the last TV channel can be heard in the background while using composite or RGB input, and there is a bit of noise on the image too. When checking with another TV, the picture and sound is perfectly fine from the Amiga, which is good since TV's are disposable while vintage computers are not so much.

July 4, 23:55 (GMT+2)

Today I borrowed an Atari 2600jr in order to modify it for composite video output. There are tons of different mods for the Atari 2600 series, and supposedly the Junior model should be among the easiest to modify with good results. Instead of tapping the TIA directly, there is a CD4050 chip which stabilizes the signal.

I followed the guideline by Brighty83, but I found that I was short of 100 pF capacitors, so I temporarily installed a 100 nF capacitor, i.e. 1000 times as much capacity.

Obviously once I finalize the mod, I will need to trim wires, insulate and all other means so I can reinstall the metal shielding on top of it, but right now it is a bit of a test to see if it is useful at all.

At first, I got no video at all so I thought I had botched it or made an error, but after a bit of fiddling, I got Pac-Man to display.

As you might see from the small image, the upper part of the display is wobbly, and the score display on the bottom is nearly unreadable, but otherwise it looked much better than I had expected.

I will probably try to get a capacitor of the right value and see if it gets better. Once I'm satisfied, I will also wire up the audio and make it pretty.

July 10, 11:35 (GMT+2)

Where did the past week go? Not much happening here at the moment. I have begun programming in IntyBASIC for the Intellivision video game, as there is an IntyBASIC programming contest going on at the AtariAge forums.

My game Alligator Swamp is planned to be a variant of a somewhat unknown Dutch game called Alligator Moeras for the Commodore PET, crudely ported to the C64. I have already got lot of ideas for improvements to the original game, ranging from better graphics, vertical scrolling trees, different fruits to night mode and even snow level which is a running gag in Intellivision circles.

Since the programming contest runs much longer than the RetroChallenge does, I might still be working on the game after the RC has ended. Hopefully I'll return to some of the other projects next week too.

July 21, 23:40 (GMT+2)

As usual, real life takes over after getting a bit into the challenge. In my case, I could blame it on waiting for some capacitors to show up, but as I've got plenty of other things to take on before the envelope arrives, it is a lame excuse.

In the past few days, I busied myself on my spare time writing an Emacs Lisp mode for the above mentioned BASIC programming. It is starting to shape up well, with built in support for invoking the compiler with customizable settings. I will add a list of built-in keywords for syntax highlighting too, just because it is fun to do. In the mean time, I teached myself a fair bit about Emacs Lisp that I either had forgotten or never knew, although my code looks horrible compared to what a seasoned, trained Lisp programmer would output.

Perhaps I'll have a go about some hardware later on this week.

July 23, 23:40 (GMT+2)

Oh, the irony! I placed an order for those caps from Futurlec on July 15. Obviously it hasn't arrived yet since there is a long distance between Thailand and Sweden, and I chose the cheapest type of shipping.

Now I started to look at those Mean Well PT-65 power supplies I bought earlier this year and plan to use one of them to replace a broken PSU in a BBC Micro. Of course they're designed to use Molex connectors of the type 5194/5195 with a spacing of 3.96 mm = 0.156" of which I don't have it at home and no local shop is selling it as well. I should've ordered those either from Elfa when I bought the power supplies, or from Futurlec with my latest order, if I had bothered to look at the datasheet first.

Of course as a desperate measure I could solder wires directly to the pins, but I'm not that much in a hurry even though the RetroChallenge is on its way to end, so I think I'll buy the connectors from somewhere and splice on the original wires on the connector.

July 25, 02:00 (GMT+2)

Tonight I have written a floppy disk full of Commodore PET games. I am aware that floppy disks written on a 1541 at best are readable on an IEEE drive like a 2040, 3040, 4040, 2031 etc; due to different sync marks the data would be screwed up if one wrote to the same disk from one of the PET drives, but since I don't plan to do that, it'll be fine.

What was not fine though was the version of my ROM set. My machine is a 3032 with BASIC 4.0 with a factory made label on the front that says 4032, but since it has the older type of motherboard and no 6545 CRTC, it is not a "real" 4032, but a 3032 with upgraded ROMs. I believe those are a bit uncommon in the PET world. In any case, it turned out several of the more advanced games, those with parts of machine code, would lock up or crash on this machine, often as expected since it is mentioned elsewhere they only work on older PET machines.

My solution to this was of course to downgrade the computer! Hello Mr EPROM burner and also Mrs EPROM eraser. Fortunately I got a small stash of 2532 chips which are pin compatible with the 2332 ROMs without the need of an adapter, and that the GQ-4X EPROM programmer actually can read and write to 2532 chips, which is not too common. So after some erasing, programming and verifying, I got the honor to open up the PET, lift the BASIC 4.0 ROMs and plop in the set of BASIC 2.0 ROMs.

Voila! The *** COMMODORE *** prompt replaced by a ### COMMODORE ### prompt, or if it is vice versa. At least all the games I tested now both load and execute as they should. Perhaps one day I'll find that I need to re-upgrade again, then I'll plop back in the newer ROM set.

It brings me to another small task to play with for the last few days of the challenge, to make an Atari style joystick adapter for the PET and also connect a speaker to get sound. Both go on the user port so it should be rather easy to wire it up, perhaps I get to it in the weekend.

July 27, 11:25 (GMT+2)

The weekend came and passed without any retro computing activities. However I have looked up some userport diagrams on the PET FAQ which I repost here for my own sake, so I have easier access to them later on.

User port from the back:

                                     1  1  1
          1  2  3  4  5  6  7  8  9  0  1  2
          =  =  =  =  =  =  =  =  =  =  =  =
         ### ######################### ######
          =  =  =  =  =  =  =  =  =  =  =  =
          A  B  C  D  E  F  H  J  K  L  M  N
          |     |  |  |  |  |  |  |  |  |  |
          |     |  |  |  |  |  |  |  |  |  |               .--------.
port 1->  8     1  2  3  4  |  |  |  |  |  +---------------|        |
                            |  |  |  |  |  |               | Audio  |
                 port 2->   1  2  3  4  |  8               | Ampli- |
                                        |                  | fier   |
                                        +--- /\/\/\ -------|        |
                                          50-500K resistor `--------'

Joystick pin diagram =>  5  [4] [3] [2] [1]
looking at back of                    \ /
male connector             9  [8]  7  [6]
The fire button (pin 6) should be connected by adding diodes from joystick pins 1 and 2 on respective port and wire them together to pin 6 with the banded end pointing to the fire button.

In theory it sounds relatively simple, now to see if I get it to work in practise. I'm just a little unsure about what an audio amplifier means, if I should connect a small (piezo) speaker directly to the source or if it will be more like a line output to go to a real amplifier.

There is a more advanced diagram in the PET User Port Cookbook by Greg Yob which instead involves +5V from the cassette port, a 47 ohm resitor, a 100 ohm potentiometer, an 8 ohm speaker and a NPN transistor capable of sinking 200 mA. I guess I may try the easier approach at first and see if I get anything out of it and then a more complex design.

August 3, 10:45 (GMT+2)

Oh, the challenge has finished! Too bad I never got anything truly finished. Last week I ordered even more parts, and since I'm a stingy one getting parts from far abroad to save money, not even the first shipment of three has arrived yet.

I suppose I'll try to wrap up some of the loose ends and disassembled computers lying around my apartment, possibly I will keep posting about the progress here even though the RetroChallenge officially has ended.

August 9, 20:00 (GMT+2)

True to my word, I'll keep this log running for a little longer.

My first Futurlec order arrived a few days ago, so I replaced the temporary 100 nF capacitor for the recommended 100 pF capacitor, and the composite video image from the Atari 2600jr became very good.

Compared to previous picture, this one was taken on a TFT rather that CRT, but it really was the capacitor change that made the differece.

I wouldn't say the image is excellent since there are slight moire patterns, but not worse than you'd get from RF anyway.

Now it is just a matter of wiring this one up nicely, add sound and position the sockets somewhere they fit.