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I’ve used the Bytesaver II numerous times to program 2708. I used Martin Eberhard’s programmer under CP/M. It works with the ByteSaver and ByteSaver II. https://deramp.com/downloads/eprom_programmers/martin_eberhard/bytesaver

Yes, it will work, but it will only use the first 35 tracks (out of 80) and only one side of the disk. The disks will interchange with other 96tpi drives connected to the Sol, but not the 48tpi drives that would have been used in the day.

Here’s a bunch of SD disks from Martin Eberhard: https://deramp.com/downloads/processor_technology/sol-20/software/northstar_sd_controller/disk_images/cpm1.4/ https://deramp.com/downloads/processor_technology/sol-20/software/northstar_sd_controller/disk_images/nsdos/

Single density works just fine in the Sol, but the small capacity (<88K) can be very limiting.

The FDC+ is not a good controller to use with the Sol-20. Any software that works with the FDC+ expects to be in an Altair with its typical console, printer, and serial I/O ports. These, in turn, are quite different than what’s in a Sol-20.

The Sol-20 DB25 is wired as DTE, so transmit data is on pin 2. Here’s the appropriate section of the schematic so you can trace the signal from the UART all the way to DB25 pin 2.

Receiving .ent does not verify that transmission out of the Sol-20 serial port is working. XMODEM, however, requires the Sol-20 to transmit in order to receive. Use the SET command in SOLOS to set output to go to the serial port, then dump a range of memory and see if it properly transmits to...

Do NOT use a delay for the XMODEM transfer. The XMODEM protocol has data throttling built in with its packet ACKnowledge requirement. Further, an XMODEM transfer is often binary data (as in this case in which a disk image is being transferred), so a delay per “line” is meaningless. Mike D

Switch settings look correct. Verify with a meter that all off positions on the 6 position DIP switch actually read open. You‘ll want to use the XMODEM send option in TeraTerm, not the plain ”send->file” option. On the “send file” picture, data is averaging 1.28KB/s, yet 9600 baud would max out...

The XMODEM transfer of the first group of tracks to write should work whether or not the subsequent disk write is going to work. Since the XMODEM transfer is not starting, there must be a serial port issue. Make sure the Sol-20 serial port is set for 8-bit word length and no parity. Selecting...

This is a great project! I’d love to build one when you have the new board proved out.

I have uploaded the MZOS 1.5 ROM and also tested it under SIMH. As expected, the version 1.5x disk images now work without having to be patched (as required previously with the version 1.4 ROM). I also updated the ReadMe file discuss the new ROM version. Thanks again for copying you version 1.5...

I need to reconfigure my MZ to run MZOS again so I can play with the 1.5 PROM and verify it’s good. Unfortunately, I can’t move my heavy machines around for another few weeks due to surgery. I’ll post the 1.5 PROM file today in case anyone else might be able to try it. I‘ll add notes as to which...

Vey nice work! My Horizon has the blue metal cover. I’d like to have a wood top, but don’t have the tools or skill.

If they’re not socketed we should probably take a different approach.

Try replacing J L S and Y on the CPU board and see if behavior changes at all. If you don’t have enough replacement ICs, try L first, or J and L if you have two replacements.

Thanks for posting! It would be great to have the 1.5 PROM instead of having to patch 1.5 disk code to use the 1.4 PROM. Reach me: directly: deramp5113 followed by ASCII 0x40 followed by the yahoo domain name. Mike D

That current consumption variance is definitely worth a first look. Leave it on for a few minutes and look for an unusually warm IC. Most of that extra current is probably being drawn by one failing device.

One easy way is to use a terminal emulator as your CP/M console and then: 1) Start MBASIC 2) Set your terminal emulator to delay 300ms after each line (e.g., TeraTerm "Transmit Delay" parameter to 300 msec/line) 3) Send the text file from the PC to CP/M machine. This essentially "types" the...

I assume the 2nd board is also an 8800b CPU board?