This past week I received another Ultimate 1MB board from Lotharek which I had ordered two weeks back, so this weekend it was time to finish up this Ugly Duckling machine and make it my daily driver, finally!
With the work I did last month to configure the board for a single-chip OS, installation of the U1MB was pretty much a piece of cake. One or two technique points that are worth mentioning for people who've never done this kind of work before ... Installation of the U1MB requires running four wires from the U1MB to the board (or the shoulders of chips) to pick up four signals not otherwise picked up from the OS ROM socket or MMU socket - Phi2, Reset, R/W and Halt. Vias for all these signals are easy to reach but the one commonly used for Reset on the 1200XL is very, very close to a small axial capacitor. Initially I had planned to use my el cheapo desoldering iron to clear out these vias from the back of the board, so that the very close-by capacitor wouldn't matter. Unfortunately, the tip of my desoldering iron is just too wide to clear out an empty via very easily. Instead, I used a 0.6mm semi-conical tip on my Hakko iron and my long-serving $6 plastic spring-loaded desoldering pump, eased along with a couple drops of MG Chem liquid flux. This technique has me heat one side of the via with the iron and after a few seconds to melt the solder, releasing the suction pump to clear out the hole. Easy peasy. Unfortunately, that little cap is kind of in the way. Fortunately, when Atari assembled the board the caps used have a little bit longer legs than strictly necessary. You can actually use a small screwdriver to push the cap to the side and gain better access to the top of the via with the soldering iron without burning or melting the plastic, so that's what I did. Once the cap was pushed aside by a millimeter or two, clearing it out with the tiny tip on my iron was a piece of cake.
Another thing of note - unlike my last U1MB, a little over two years ago, this time Lotharek included a four-wire connector with plenty of fine-gauge wire pre-installed for the jumpers to the board. This makes installation much easier for the part-time hobbyist who may not like to keep rarely-used tools and connectors around, or spend the money to buy them for a single job. So thumbs up to Lotharek for this little helpful touch.
Once I'd verified that the board would boot and was functionally stable, I removed the jumper connector, secured the four wires together with a small zip tie, then twisted them into a tight bundle and tucked them neatly up and around the U1MB before plugging the connector back in. The board is mounted in one of the now-vacant holes from the RF shielding, With the mounting rod screwed down tightly on the support posts using two of the included nuts, and the MMU cable folded and routed underneath, it sits very securely at the back of the machine next to the AC rectifier.
Two years ago I had tried to mount my first Ultimate 1MB into another 1200XL but the combo in that machine was never stable - the real-time clock kept resetting, sometimes the board graphics and text were corrupted and the computer would lock up. That same U1MB went instead into an 800XL and has been completely perfect there for two-plus years now. I never figured out why that U1MB wouldn't run well in that machine but based on that experience, this time I decided to do some stability tests before I trust it. After it booted up yesterday, I tried a number of cartridges, with and without SDX enabled, I reset and rebooted the computer multiple times, and let it run for over 4 hours without issue. Today I put my SIDE2 cartridge into it, ran programs off the CF card hard drive, saved and loaded files and let it run for about 4 hours again, also without issue. (*)
So I powered it down, cleaned up the board, reassembled the computer, and flashed Jon's latest-release BIOS, SIDE Loader, and PBI BIOS, then I updated SDX, configured my OS and BASIC slots as I prefer them, and voila! The machine has run all day and it's been rock-solid.
So until I get the urge to put an internal CF card IDE hard drive solution into the machine, or maybe a stereo POKEY board or something, this one is done and ready for daily use at long last. Huzzah.
Here's where the Reset line is connected, right above that little capacitor I mentioned:
All four wires: Phi2, Reset, R/W and Halt:
Assembly more or less done, ready to test:
Ta da, it works!
Flashed with Jon's latest firmware, and ready for duty:
(*) Hat-tip and thanks to Jon, again, for his tip about the SIDE2 cartridge in the 1200XL; at his suggestion, I used fine-grit sandpaper to sand off about half a millimeter from each side of the SIDE2 cartridge case and now the cartridge fits into the 1200XL cartridge tunnel perfectly. You still don't have the same ease of access to the sliding switch on the front of the cartridge but the cartridge itself slides in and out easily, with no changes required to the 1200XL cartridge tunnel at all.