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System Description
What is the Lt.
Kernal (LTK) subsystem? And, how did it get its strange name?
The Lt. Kernal is an integration
of SCSI (Small Computer System Interface) electronics,
Winchester fixed disk storage technology, and a professional-grade disk
operating system (DOS). SCSI provides an intelligent, high speed parallel
data bus between computer and hard drive, and the DOS gives the computer
the capabilities needed to effectively manage and utilize the drive's capacious
storage. The result is a Commdore 64 or 128 on steroids, a system
that appears to be an eight bit microcomputer but embodies the personality
and features of a high-powered minicomputer.
Prototyped in 1984 and released
for production in early 1985, the Lt. Kernal revolutionized the concept of
mass storage for eight bit Commodore machines and set the standard by which
later such systems would be measured. The C-64 version of the Lt.
Kernal was up to 100 times faster than the Commodore 1541 floppy drive, and
the C-128 version running in FAST mode was about 170 times faster. The
Lt. Kernal DOS introduced many new features to the system, such as the ability
to execute a program by typing its name and pressing the Return key.
As is characteristic of any system
that implements SCSI-controlled mass storage, the Lt. Kernal hardware consists
of two major components: the hard drive itself, mounted in an external,
self-powered enclosure, and a host adapter that plugs into and is powered
by the computer's expansion port (see the photo at the top of this page).
The host adapter and hard drive assembly are interconnected by a data cable,
which is what embodies the SCSI bus. An accessory device called a
multiplexer may be used to gang multiple computers—in any combination—to a single hard
drive unit, giving each machine transparent access. Advanced programming
techniques can make a multiplexed system behave much like a multiuser minicomputer,
resulting in a remarkably powerful shared data storage and retrieval system.
Since the Lt. Kernal is designed around SCSI, multiple hard drives may be
attached to the system, allowing a maximum aggregate storage capacity of
approximately 330 megabytes.
Almost all of the Lt. Kernal magic
occurs in the host adapter, which "adapts" the internal address and data
bus hardware circuits of the Commodore computer (the "host") to the SCSI
bus in a way that is invisible to the rest of the system. As no eight
bit Commodore computer has ever had a built-in DOS, let alone one suitable
for use with a high capacity SCSI hard drive, the host adapter includes 16
kilobytes of RAM to provide space in which to execute a sophisticated and
powerful DOS that acts as an extension to the standard Commodore kernal operating
system. Complex electronic logic in the host adapter maps the DOS in
and out of processor address space according to the operation being performed,
resulting in a high degree of compatibility with the standard Commodore kernal
and memory map.
As for the Lt. Kernal name, it
was coined early in the product's development as a pun on the way in which
the prototype operated. In order for the Lt. Kernal's DOS to function
on the C-64, it had to be linked into the kernal. In the prototype,
this was accomplished by running the DOS in the $E000 block of RAM underneath
the kernal ROM. Due to the architecture of the C-64, getting the Lt.
Kernal's DOS to run at all was a major programming feat. It was, in
fact, more than major, but still beneath the kernal. Hmm...more than
a major but below a kernel...er...colonel. That meant the DOS was actually
a Lt. Colonel...er...Kernel. Arrgghhh!!! However, Commodore
had misspelled "kernel" and thus the system was christened Lt. Kernal.
Production units moved the DOS into RAM inside the host adapter, but the
name stuck.
In the late 1980s, several competitors
to the Lt. Kernal were developed, most notably the line of hard drives
produced by Creative Micro Designs (CMD). However, none of these
systems has ever approached the performance and sophistication of the Lt.
Kernal design, and the Lt. Kernal continues to be the apex of eight bit
Commodore-compatible hard drive subsystems.
If your primary
use of a computer is for productivity, you should consider a Macintosh or
a PC running Linux. However, if you are interested in experimenting
with eight bit Commodore hardware, the Lt. Kernal subsystem is an ideal
development and testing platform. To get the most from your Lt. Kernal,
this is the site for you!
Each of the other
sections of this website cover the entire spectrum of the Lt. Kernal, including
the host adapter, multiplexer, hard drive(s), DOS and much additional technical
information, such as installation procedures, schematics, timing diagrams
and file downloads. We hope that you find this information useful. If you have any questions, need further information
or would like to add to the site's content, please E-mail the author.
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