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Author Topic: JiffyDOS bugs in Plus/4 version  (Read 1990 times)
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« on: December 06, 2015, 12:12:49 PM »

     Back in the day, Maurice Randall developed versions of JiffyDOS for the VIC-20 and Plus/4.  I was a beta tester for the VIC-20 JD, and James C. was a beta tester for the Plus/4 JD.  Though I casually tested VIC-20 JD and found no faults, James was able to find bugs in the Plus/4 JD.  Here are his results, as reported in 2011 on comp.sys.cbm:

Bug #1: @Q gives "Device Not Present" error if disk drive is not on.
So does @F. I haven't gotten around to all the @ commands yet, but
these two should work even if the drive isn't on, as they disable
JiffyDOS or the JiffyDOS function key definitions -- disk drive
shouldn't matter. (Maurice replied: "The 64 and 128 do this as well.
The way the code is written would take a lot of work to eliminate
this. This is generally not a problem since in most cases, a disk
drive is in use and JiffyDOS is a "Disk Operating System". Personally,
I agree though, that CMD should have accounted for these two commands
when a disk drive is not present.")

Bug #2: Key 6 is "LIST"+CHR$(13), contrary to manual (manual states
key 6 should be left arrow, SAVE).

Bug #3: Function key definitions not disabled during program
20 KEY
... the JiffyDOS function key definitions are displayed, and pressing
F3 captures an @ in A$. Proper function key disabling should redefine
the function keys to Commodore's default definitions? Manual states on
page 45 under @F: "The JiffyDOS function keys are active only in BASIC
direct mode and are disabled when programs are run...."

Bug #4: C16 program "Leaper" has a multi-part loader like many UK C16
games. (1) A boot file is loaded, which (2) displays a copyright/title
screen as it (3) loads a graphic title screen (some play music), then
(4) the copyright/title screen is displayed again while (5) the actual
game code is loaded. Disk operations occur at steps 1, 2, and 4. The
bug is that the game is corrupted upon final load (at the end of step
5). Either the game doesn't start (hung on copyright screen) or the
graphics are corrupted. (This may go back to the JiffyDOS 255 byte
buffer at the top of memory. A lot of commercial C16 games fool the
Plus/4 into reporting 16K memory (12288 bytes free) even after a soft

Bug #5: C16 program "Skyhawk" hangs upon loading its' loader program.
A one-block file shouldn't cause me to hit the reset button after 30

Bug #6: Pressing F2 ("/", load from directory listing) will error out
with "?File not found error" apprxomately half the time. It may be due
to the 1541 not through spinning down after displaying the directory
with F3 ("@$"). The 1541's red activity light is left solidly on.
OPEN15,8,15;CLOSE15 from direct mode closes whatever file is being
left open. @ is not turning the red light off when this happens
(because there's no disk drive error to report?).

Bug #7: "ACE" from the same page errors out during its' boot process
as well. It dumps me into the MONITOR with a flashing 1541 light and I
can't get out of MONITOR to read the error channel. I have to hit the
RESET button, which clears the 1541. The only way I can load ACE is to
turn off JIffyDOS at both the computer and the drive. This title has a
disk-directory copy protection, one must type LOAD"ACE",8,1 for it to

Bug #8: I have a customized "Plus/Extra". It hangs during the boot,
after displaying the first screen (insturctions for a Notepad that
comes up by pressing Commodore-Control), before it loads the selection
menu. Error given is "File not found in line 750". About half the
time, I can type GOTO750 and it will finish loading; the other half of
the time, the 1541's light stays on (not flashing) and goes back to
the "File not found in line 750" error. Once again,
OPEN15,8,15;CLOSE15 turns the red light off on the 1541. If you want a
copy of this one I'll email it to you, as the custom one isn't on my

Bug #9: File copy doesn't work right. I've only attempted to copy the
"Action Pack" as referenced in the last message, and the copy won't
run even if I turn off JiffyDOS on both the Plus/4 and the 1541. It
seems that the copy process is corrupting these ML files.

Bug #10: If I put a file on the destination disk before file copying,
then the first file on "Action Pack" disk isn't copied. The filenames
are different.

     To the best of my knowledge, both VIC-20 and Plus/4 versions were transferred to Jim Brain of Retro Innovations, and there have been no corrections in any of the bugs.  Those are the versions sold by him currently.

          Robert Bernardo
          Fresno Commodore User Group
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