BillC

The company name is Software Publishers, Inc. of Arlington Texas, at least that's what's in the ATR8000 manual. https://www.bizapedia.com/tx/software-publishers-inc.html

When @MEtalGuy66 reproduced the MIO he updated the original serial/printer ports to PC compatible pinout, this allows the use of commonly available cables. This would be DE9 for serial and DB25 for printer. In addition changing the FDD edge connector to a 34-pin FDD type header would allow the use of more commonly available floppy cables as well.

The reason the 8-bit computers of the time, and the ATR8000/8500, used DRAM was simply because of price. At the time static RAM was much more expensive that DRAM, even with the refresh circuitry required by the latter. In the 90's there were 486/Pentium motherboards with fake cache memory chips to reduce cost. These days most SRAM is less expensive than DRAM and also occupies less PCB area even when just the RAM is considered, even more PCB area is saved when considering no refresh circuit requirement.

This is quite a project, you might want to contact @MEtalGuy66 about the issues he had reproducing the MIO. Why stay with 4164 DRAM, most modern upgrades/devices have switched to static RAM?

He's not an AA member, his contact information has been posted already.

The reason for a converter chip is that legacy RS232 signals are +12V/-12V, which the Atari wouldn't be able to recognize and which could also do damage. The converter chip changes these to TTL level signalling compatible with the Atari.

I believe that the XEX extension came about because of emulator software on the PC. EXE files for the emulated system were renamed XEX so that they wouldn't be mistaken for X86 executable files.

I believe with the TK-II the PC keyboard function keys are/can be mapped as the Atari console & function keys.

The U1MB DOES NOT add a PBI/ECI, the Atari it's installed in may have this feature. If installed in a stock 1200XL/NTSC 65XE/XEGS there is no parallel interface. The Incognito does add PBI to the 800, but would not be active in 800/Colleen configuration

The inverter is required as well, TTL logic chips have a fixed output delay, the idea is adding these additional components onto a 74HC14 will modify the delay of certain outputs to the desired values.

I recommend the Syscheck, I had a 130XE with 44 out of 48 red blocks and my Syscheck V2.1 identified only 2 bad RAM chips. The V2.1 also functions as an external OS chip(selecting from 4 different firmware), as replacement 64KB base RAM, and the V2.2 adds the ability to function as a memory expansion.

The delay for Europe was most likely because of the different(PAL/SECAM) video standards, which even require different ANTIC/GTIA chips. Japan uses a slightly modified NTSC(NTSC-J) standard, the brightness level is a little different and the audio is on a different frequency sub-carrier for the RF output but these wouldn't require significant modifications from the Canada/USA NTSC-M version. https://en.wikipedia.org/wiki/NTSC-J

Popcorn is sometimes used as a bio-degradable alternative to styrofoam peanuts.

BASIC programs can't be saved to disk unless DOS has been loaded first, booting DOS from an ATR mounted as D1: is the first step. There are only a few DOS's that can access large partitions, SpartaDOS is my preference. The disk based versions of SpartaDOS allow up to 16MB per ATR/partition, while the later releases of SpartaDOS-X allow up to 32MB.

I'm would think the 6 headers are just inserted into corresponding IC sockets on the main PCB, the lowest header in the bottom image in post #44 can be seen plugged into a socket.