On the tools page @ http://osi.marks-lab.com/software/tools.html
you can find the C1-C4 Dump program & source.
The readme included in the archive has the following:
This is an OSI dump utility for OSI C1/C4 systems with disks.
This program is loaded via the OSI 65V ROM monitor.
Transfer can be as ASCII HEX dump or XMODEM-CRC binary dump.
Requires 8K of working RAM and a serial connection to transfer data.
Connect the OSI C1/C4 system to a PC via a serial cable. Ensure
you have the correct baud rate for your system (9600 baud?) and 8bit
no parity, 1 stop bit, no flow control. (This assumes your OSI has
been modified to use RS-232.)
Reset the OSI system. You should see the C/W/M? prompt. Choose 'M'
to enter the ROM monitor, press 'L' to begin input via serial port.
(remember all OSI commands are upper case)
Begin sending the c4dump.lod file using a RAW ASCII send from the PC.
The C4dump program begins loading at $0400 which is also the entry point for
the program. When the c4dump.lod file ends, it should automatically start,
and display the message "OSI DUMP ON SERIAL NOW". If it does not start,
RESET the OSI, at the C/W/M? prompt enter 'M' then type 0400G.
Once running, the terminal should show the disk program's menu below:
OSI Serial Disk Dump
1. Dump Raw Image
3. Select Drive
4. Set Drive Type
5. Set Serial Divisor
6. Set Xmodem/Hex xfer
Drv=A/5.25 Baud@1x Hex
The options are as follows:
1 - dumps the selected disk image in HEX or as XMODEM/CRC as selected
3 - select disk drive A - D (1 - 4)
4 - select either 8" (79 track) or 5.25" (40 track) disk drive type
5 - program the ACIA clock divisor, either normal (/16) or fast (/1)
divide by 1 allows you to transfer a disk image at 4800baud on a machine
wired for 300 baud (300x16).
6 - Set desired transfer mode XMODEM or HEXADECIMAL. When using HEX you will
need to convert the resulting data into binary using a program like deHex.
Xmodem transfers binary images, no additional processing is needed.
Once you have selected the appropriate options for your setup, enter '1' and begin
receiving data with your terminal program.
Hope this helps,