a E i - Commodore Is Awesome

El
F
he purpose of these programs is to
copy whole disks on tape, so as to store
them in a convenient low volume form.
The backup on tape proceeds at 16
times the standard CM speed (even
faster than standard turbo tape
format!) This means that the 175K of a
1541 disk drive are packed on only five
minutes of tape.
Data is saved in three steps each of
which saves approximately 60K of
data, in track increasing order. All
blocks are transferred, even free ones.
This ensures that a disk copy will
always fi t the .atne length of tape, a
useful feature if you want to rewrite
updated data over an already existing
copy. (However there is one exception
— if blocks do not read properly, they
are written in shortform so the entire
copy will be shorter. It also means that
it is not really worthwhile to use this
program to save nearly empty disks.)
the program is made up of two
complimentary parts: MCOPYTD
and MCOPYDT. MCOPYTD saves
data on tape and MCOPYDT reads it
back to disk. These programs can also
be used with the 1571 disk drive in 1541
mode. However only single sided disks
or the first side of a double sided one
can be saved with this version of the
program. To use MCOPY, just RIJN
the two Basic programs (when keying
these, don't forget the DATA
000,000. lines, since the checksum
does not detect such omissions). Of
course, since they are created on disk,
a formatted disk must be in the drive.
Getting Started
Load MCOPYDT (disk to tape).
Make certain that you are past the
leader of the tape.
Put the disk to be copied in the drive,
Run MCOPYDT: the introductory
message appears_
Press record and play (the tape does
not move yet).
C64 PROGRAMA
isk Archive
A handy set of two programs to help you save your
programs to tape in a convenient firm.
By Jean Lebailley
Press RETURN. The program starts to
read the disk, then transfers its contents
on to tape in three steps. DO
NOT stop the recorder between steps.
When the process ends the message
"END OF COPY" appears, along
with error messages if needed. Note the
tape counter value.
An error does not always mean
that the whole copy is bad. However
when the tape is reread the same error
will be recreated on the new disk (also
the copy on tape will be shorter).
Therefore, it is up to the user to decide
what to do when such an error occurs.
Reading Back
Load MCOPYTD (tape to disk).
Put a new disk in the drive.
Put a cassette into the datasette. Position
tape to read the first of the three
subsections previously saved. Reading
over the end of other data does not
matter since MCOPY only starts
reading after having found a special
synchronising header.
Run M CO P Y D
The read back proceeds in the same
way as MCOPYDT, in three steps.
At the end of the process, the
message "END OF COPY" appears.
Remove the disk from drive (it doesn't
matter if the red LED is still on, this is
normal).
Two kinds of errors can arise
during the readback process. Unfortunately,
they are almost always fatal.
WRITE ERROR TRACK NN —
means that the drive could not reread
the data, it just writes on that track.
This is usually caused by a bad disk.
Try again with another one (see also
TAPE LOADING ERROR).
TAPE LOADING ERROR — The cassette
could not be read back properly.
This is usually caused by one of the
following:
YOUR COMMODORE january 1987
58
Bad tape; use only good quality cassettes.
Although the encryption
scheme used to write on tape is very
reliable by itself, a singly false bit in the
601(4 causes the error. I previously
wrote these programs using standard
turbo routines but an error occured
nearly every time in one of the three
sequences, it was also slower and the
length of tape used was data dependent.
(10 took less time to save than 'FF's.)
Try to save 60K with standard turbo
on the same tape you are very likely to
see several errors, not just one.
Read head is dirty, clean it.
Read head has gone out of alignment
since the tape was written. Realign it.
The recorder has been knocked or
moved during read or write: this causes
tape speed changes that can lead to
errors.
The tape has been damaged, usually
unrecoverable.
Too much friction inside cassette.
Rewind it and retry.
You can (and it is recommended)
leave blank space on tape between
disks: to do that, just press the ! key
and the recorder starts. Stop by pressing
any other key.
I
N
BS 1 0 R EM
E SC 20 REM CREATES MCOPYDT ON DI
F SK
T
91 30 REM
Y
53 40 REM FAST DISK TO TAPE BAC
E
KUP PROGRAM
T
B9 SO REM SALTS UP TO 12 SINGLE
7
SIDED DISKS
.
83 BO REM
R
14 70 REM ON A SINGLE CEO CASSE
.
TIE
F
OF BO R EM
n
T e3 90 REM WRITTEN BY J.LEBAILLY
E
EB 100 REM
36 110 OPEN2,8,2,"e0:MCOPYDI,P.
FS 120 PRINT#2,CHRS(1);CHRS(B);