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The Memotech MTX Series |
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MEMOTECH DISK SYSTEMS
There were a number of different disk upgrades available for the MTX
range, including various floppy disk interfaces as well as a
hard disk option for the FDX,
called the HDX. The hard disk
upgrade was very expensive though, and I'm not sure if (m)any
were actually sold; here, I am going to concentrate on the floppy
disk drive options.
Floppy Disk Systems
A word about floppy disk technology
It should be remembered that floppy disk drive heads make
contact with the media (diskette), in contrast to a hard disk,
where the heads "fly" over the surface of the disk
platters. As the
floppy media ages, particularly lower quality media, it can
degrade in a number of ways, including breakdown of the magnetic
coating, mould inside the protective jacket, etc. These issues,
as well as specs of dust, can lead to scoring of the media which
can not only effect the particular diskette in use, but also any
other media subsequently put into the drive if the debris gets
deposited on the read/write heads.
It is a good idea
to closely inspect any old diskettes that you plan on putting
into the floppy drive before use. It is also important to
periodically clean the drive heads to clear any accumulated
magnetic oxide particles and dust that would otherwise damage
the media and/or drive.
The design and construction of 3.5" floppies means that they
are much less prone to these problems than 5.25" floppies are.
Memotech Floppy Disk Options
Disk Operating System
All of the disk system released by Memotech use the same
underlying software, i.e., they are ALL based on the Memotech
CP/M system.
CP/M Systems
When running under CP/M, operation of the Memotech disk
systems is as you might expect and is pretty much the same as
floppy disk operations on other CP/M systems. Starting the system
requires that the system is booted from a system disk
which loads the CP/M system into memory as described in more
detail on my CP/M Structure
page.
In short, the disk system ROM looks for the boot sector of a
system disk and loads the essential parts of CP/M, including the
disk configuration definitions, into RAM. On an
FDX system, once the system is
loaded, the boot disk can be swapped for non-bootable program
and data disks as needed. To ensure that CP/M is made aware of
the disk change and can properly update the directory structure,
the user "logs on" to the new disk by issuing a <ctrl><C>
command from the command processor. (This is not the case for
SDX disk systems - see the SDX page
for more details.)
Under CP/M, the first two tracks on the disk are reserved for
CP/M and store the BIOS, BDOS and CCP. Since the tracks are
reserved, there is no penalty for making every user disk a
system disk and being able to boot from it.
Non-CP/M Systems
Memotech's non-CP/M disk systems operate in a very similar
manner, but with some important differences that the user must
be aware of. Unlike other 1980's home computers, such as the
BBC micro, the disks used for
Memotech's BASIC disk systems must ALL contain a bootable CP/M
operating system disk.
After the system and disk drive(s) have been powered on, the
user must explicitly restart the disk system by issuing a "ROM
x", (where "x" is 3 or 5), command from BASIC to initialise the
disk system, load the essential parts of the disk system into
RAM and read the disk directory. To cater for differences
between the CP/M and non-CP/M systems, the non-CP/M ROM patches
the disk code as required during the boot process.
If the disk is changed, another "ROM x" command must be
issued to make the system aware of the new directory contents.
When preparing a new disk for use, the USER FORMAT and USER
SYSCOPY commands must be used to make the disk bootable which
requires that the user already has a bootable disk from which to
copy the system files. As with
the CP/M system, there is no reduction in the usable space on
the disk by doing this.
Credits : Some of the
information on the operation of the SDX was posted by Andy Key
in the
Memotech Group on
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