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1541 tutorial 1
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2022-08-26
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Origin of the 1541 Disk Drive
====== == === ==== ==== =====
by Joel Ellis Rea
First there was the Commodore 2001
Personal Electronic Transactor (PET).
It was one of the first personal com-
puters on the market. It had a whop-
ping 4K of RAM, an 8K BASIC in ROM,
and a Kernal to control input/output
and other system operations. It used
Commodore BASIC Version 1. There were
no disk drives then, but provisions
were made in the form of an IEEE-488
General Purpose Interface Bus. It
also had the funniest little keyboard
you ever saw!
Commodore then invented the 2040
Dual Floppy Disk Drive. It was an in-
dustry first. Instead of requiring
the main computer to control every ti-
ny detail of disk drive operation, not
to mention loading a (large) Disk Op-
erating System (DOS) into the compu-
ter's RAM in order to use the drive;
it was an intelligent drive, with its
own computer system inside, and its
own DOS in ROM! By simply PRINTing
commands to its command channel, BASIC
users could SCRATCH, RENAME, and COPY
files, and DUPLICATE an entire disk
without any further help from the com-
puter. Only problem was, they could
not SAVE or LOAD programs, or use data
files.
The problem was in BASIC V1. It
didn't know about the timing involved
with actually transferring data back
and forth between the computer's RAM
and the disk drive's computer. So,
Commodore created Upgrade BASIC (now
known as BASIC V2.), and put it into
a new PET, called the 2008. It had
8K of RAM, a REAL keyboard (unlike o-
ther companies, Commodore NEVER tried
a rinky-dink keyboard again!), and it
could use the disk drive!
But the 2040 drive had its faults
as well. It couldn't handle random-
access files (one of the most impor-
tant advantages of a disk drive over a
tape drive!) without a LOT of effort
on the user's part, it couldn't trap
errors correctly, it required the user
to: OPEN15,8,15,"I":CLOSE15 every time
the user wanted to change disks, and
it couldn't seem to center the disks
properly.
So about the time Commodore came
out with their 3008 PET computer (with
BASIC V3, with very minor differences
from V2.), they came out with the 3040
Dual Disk Drive. This had DOS V1.2 in
it, which corrected the problems with
error trapping. But they didn't fix
much else. Also, people were getting
tired of having to type OPEN15,8,15,
"R0:newfilename=oldfilename":CLOSE15
to rename a file, when their Apple-
owning buddies could do the same with
RENAME oldfilename,newfilename.
Almost immediately therafter, the
Commodore 4016 PET came out. It had
16K for starters (expandable to 32K),
and BASIC V4. This version of BASIC
had nice disk commands like CATALOG,
SCRATCH, DLOAD, DSAVE, BACKUP, COPY,
etc. These commands simply translated
themselves into the old commands the
disk drive understood. So COPY D0,
"oldfile" TO D1,"newfile" got sent to
the disk as the good old "C1:newfile=
0:oldfile" stuff.
Along with the PET 4016 came the
4040 Disk Drive. It had it all! Be-
sided fixing the hardware problems,
it had DOS V2.1, which supported RELA-
TIVE FILES! (What other people called
Random files, but thay used a differ-
ent terminology so as not to confuse
the old disk drive owners who were do-
ing it the H-A-R-D way!) The new DOS
also performed an automatic "I" com-
mand every time it detected a disk
with a different ID, so that the user
didn't have to unless he had two or
more disks with the same ID (the two
characters that appear after the disk
name in a directory listing). It also
used a slightly different disk format
from the 2040's and 3040's, so that a
disk made on a 2040 would have to have
its files copied to a 4040 disk drive.
Later, Commodore came out with the
Commodore Business Machine (CBM) 8032.
It had BASIC V4, 32K of RAM, a 12-inch
80-column monitor (the old machines
had smaller 40-column screens), and a
more business-like keyboard. Indeed,
it was a business machine!
A business machine needs a business
disk drive. So Commodore presented
the 8050 disk drive. It used a double
density format that got over twice as
much data on each disk. It also could
tell if a disk drive door had been o-
pened, and automatically did an "I"
command when the door was shut again,
so that the user NEVER needed to do
that, no matter WHAT his disk ID's.
Later came the 8052 double-sided
drive, and the D9060 and D9090 hard
disk units that could store 2, 5, and
7.5 Megabytes (1 Meg = 1024 K!) of
data!