Spare Time Gizmos
SBC6120 User's Manual
03/09/2003 1:35 PM
Page 22
That said, it isn't hard to find copies of OS/8 on the Internet, and a little
surfing should lead you to what you need.
4.5.1 Building a bo otable IDE disk on the PC
Once you've built a bootable OS/8 ID01 disk image file on your PC, you can take your SBC6120's
IDE disk and physically connect it to the PC, and then use the MKID01 program to transfer the
image file to the disk. Most likely you will want to connect your SBC6120's IDE disk to the PC as
a slave drive since you'll still want another master IDE disk containing Windows (or at least DOS)
for booting the PC. It's conceivable that the SBC6120's disk could be the only IDE disk on the PC
and the PC booted from either a floppy or a SCSI disk, but that's left as an exercise for the
reader.
After you've temporarily connected the SBC6120's IDE disk to a PC, you can use the MKID01
program to write an ID01 disk image from the PDP-8 emulator to the physical drive. For example:
MKID01 -u1 -w0 os8.id1
The
-u1
option tells MKID01 to use IDE unit #1 (the primary slave) as the target drive,
-w0
instructs it to write SBC6120 partition 0, and
os8.id1
is the name of the ID01 image file from the
emulator. The PDP-8 emulator must write the image file in exactly the same format that the
SBC6120 uses (WinEight does) as MKID01 simply copies the entire file, verbatim, to the IDE
disk.
The Spare Time Gizmos
FLX8
program is also able access a physical IDE disk in the SBC6120
OS/8 format, and it knows how to transfer files between DOS and OS/8 file systems. If you have
other files you want to copy to your SBC6120 (source files, games, whatever!), now is a
convenient time to use FLX8 to initialize one or more other partitions on the SBC6120's IDE disk
and load them with files from the PC.
You can now disconnect the IDE disk from your PC and reconnect it to the SBC6120. If you
changed the disk to a slave drive be sure to change it back to a master before reconnecting it,
since BTS6120 will not recognize a slave drive. If all is well you should be able to power up the
SBC6120 and use the
B ID
command to boot OS/8 from the IDE disk.
4.5.2 Download a b ootable OS/8 image over the serial port
It is also possible to take an ID01 or VM01 image file on the PC, convert it to ASCII text, and then
download that text to the SBC6120 over the console serial port. The BTS6120 firmware contains
two commands,
RL
and
DL
, for just this purpose. The disadvantage to this scheme, naturally, is
that it is slow. An image of a 512kb RAM disk requires approximately 2199k bytes in ASCII and
takes about forty-five minutes to download; an IDE disk partition would take about three hours.
The MKDLTXT program will convert either a VM01 or ID01 disk image to ASCII text in a format
suitable for BTS6120. For example:
MKDLTXT system.vm1 >system.txt
will convert the file VM01 image
system.vm1
to ASCII text and write the result to standard
output, which is redirected to the file
system.txt
. The same command is used to convert an
ID01 image to text - MKDLTXT automatically determines the input type by the file extension.
The converted text files include a checksum for each disk block which BTS6120 uses to guard
against transmission errors, however BTS6120 does not implement any special protocol or
handshaking (e.g. X-Modem or Kermit) for transferring the text. The PC software must be
careful, therefore, not to send data faster than the SBC6120 can process it. BTS6120 prompts
for each new record with a ":" character, and the PC terminal emulation software should wait for
this prompt before transmitting each line.
