#04 30 ноября 1995

Part 7 - Technical forum.

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* PART 7 - TECHNICAL FORUM *
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This issue, I have received a letter:

"I  am  now the happy (?) owner of a Timex
disk  drive  for the Spectrum. I bought it
at  a  sale  organised by my university. I
also own two Timex 2048 machines.

"The drive seems to be some predecessor of
the  famous  FDDЗO00 drive, and I think it
is  called  FDD 3. I have 3 inch and 5 1/4
inch  drives  connected to the controller.
The  3 inch drive came with the controller
and  the 5 1/4 inch drive came from my old
XT. I don't have any manuals for the drive
but  I  have  read  old  issues  of Polish
computer  magazines  and  there  was  some
information  about  this drive. It seems I
need  a  diskette  with  TOS  in  order to
format another diskette, and it seems that
the   drive   controller  will  not  start
without  this  diskette  because  when the
controller  starts  it  reads TOS into its
own internal RAM.

"The   problem:   I  don't  have  the  TOS
diskette.

"What  I  need  is an image of a formatted
diskette  so I could format more and enjoy
my  old  Timex.  By  "image"  I  mean  all
sectors  from  the diskette written to one
160K file. think I can write a program for
my PC to format diskettes to 40 tracks, 16
sectors,  256  bytes per sector, and write
this image there.

"Does  anyone have a TOS diskette for this
drive, or an image of it?"

DOMINIK BEHR

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Tech Ed's reply:

Firstly,  with this equipment being marked
TIMEX, I would guess it's intended for the
American   market.  Perhaps  some  of  our
American readers would be able to help.

Second, you mention a 3-inch drive. Do you
mean  CF2  type?  These  disks are getting
rare,  but some people using Amstrad PCWs,
CPCs  or the Spectrum +3 may know where to
get  them.  If you mean the PC type, these
are 3 1/2 inch, and very common.

Thirdly,  you  might,  quite  possibly, be
able  to make a 5 1/4 inch PC drive format
a  disk  suitable  for the Timex. It might
help you, but it might not.

Not knowing this drive, I am throwing this
query  open.  If anyone knows how to solve
this,  perhaps  you  could let me know. My
details  are  at  the end of the technical
section.

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TECHNICAL WRITES

This  month,  I have written an article on
mass   storage   devices  and  ability  to
emulate.   Once   again,  as  a  PC  user,
emulation  is  generally from the PC point
of view.

Mass  storage  is  a  central  part  of  a
computer  system. Without it, the computer
would forget everything when switched off.
The Spectrum was supplied with the ability
to  use audio tape, usually in the form of
the  Philips  compact  cassette,  as  mass
storage. The advantage of this was that it
was  the  one  form  of  storage which was
available  to  everybody, with most people
either owning a cassette recorder or going
out   to   buy   one  when  the  need  was
discovered.  The +2 and +2A models had the
data recorder built in.

Tape  had  the  advantage that most retail
software  was  supplied  on  cassette. The
major  disadvantages  were finding a block
on  cassette,  the fairly slow speed, and,
in some cases, poor reliability.

Of  the  emulators  available  for the PC,
several  handle tape. SPECTRUM has limited
tape  handling, and Z80 is well-specified.
Others   exist,  but  in  most  cases  are
limited.

Sinclair  planned to launch the Microdrive
system  in  1982.  Unfortunately,  it  was
delayed,  and then needed the ZX Interface
1 before it could be fitted. The media was
a  small  cartridge  containing  a loop of
tape.  The  system  was  much  faster than
tape,  but  access  time  was still fairly
slow.  Cartridge reliability was a problem
occasionally,  and  the  vast  majority of
cartridges  had  at least two bad sectors.
Storage  capacity  was  in  the  region of
90-100K.  Up  to  eight  drives  could  be
fitted.

Emulators  are  unable  to handle the real
cartridges,  but  Z80  handles a file type
called  MDR,  which  emulates a microdrive
cartridge.  It  is  reasonably possible to
devise  a  system  linking a real Spectrum
with   microdrives   to  a  PC,  and  copy
cartridges that way.

Other mass storage systems began to appear
over  the  years which followed. Rotronics
launched  the WafaDrive. Some people found
these  very  useful,  but  the  media  was
somewhat non-standard. Printer interfacing
was  provided  by  the  drive,  which also
proved  useful  to  many  users. As yet, I
have  never  seen  a  system emulating the
WafaDrive.

Storage   systems   using  standard  disks
proved  to  be  quite  popular.  The  Beta
system,  which was fairly popular, has the
advantage  that  only  a simple program is
needed   to   read  the  disks  on  a  PC.
Kempston,  best  known  for their joystick
interface,  also  launched a system. Miles
Gordon  Technology  designed  the Disciple
interface,  and marketed the +D, which was
almost   the   same  thing.  The  Disciple
interface    was   compatible   with   the
Interface  1  network  system, among other
things.

The  MGT interfaces can be emulated easily
with some emulators. For the PC, Z80 works
well.

You  may  have  noticed that I have so far
omitted the Opus Discovery. There were two
different  models, one which had one drive
and  a  joystick  port,  upgradable to two
drives,  and  one which had two drives and
no  joystick port. A parallel printer port
was included, which used the same commands
as  the Interface 1 serial port. The Opus,
in  common with many of the other systems,
used  a  BASIC command set similar to that
used  by  microdrives. Most did suffer due
to  them  not  being microdrives, and some
things   were   different.   Some  used  a
completely  different set of commands, the
WafaDrive almost setting the standard.

The  Opus  system used 40-track 3 1/2 inch
disks.  The major disadvantage of these is
that  it  is difficult, if not impossible,
to  make  80-track  drives read the disks.
Some  systems  which  were upgraded rather
late  in time were fitted with an 80-track
second  drive.  These  are  the exception,
rather  than  the  rule, and are not worth
emulating.

The  only  other  system I knew of for the
older  machines  was the Clive Drive. This
was  VideoVault's  3-inch drive, which may
have used MGT firmware. An attempt to make
a  standard disk drive for pre-+3 systems,
it was a failure.

The  +3  included a CF2-type drive. A fair
amount  of  software was released on disk,
and this was as close as could be got to a
standard. The +3 would take an Amstrad FD1
as a second drive. The +2A was intended as
a  "lower" machine that could be upgraded.
The  SI1  and  up  to  two  FD1s  could be
attached.  I  have  never  known of one of
these being used.

Many  users wanted a way to transfer their
software,  in  particular,  games,  to the
high-speed  devices.  Some solutions using
convertor   software   existed,  but  some
programs  could  not be handled. Some very
old  games  could  easily be hand-blocked.
Some     included     instructions     for
transferring   to  microdrive,  and  these
functions  often  worked  with  the  other
drives using microdrive commands.

Probably  the most effective solution came
by   way  of  the  Multiface.  Created  by
Romantic  Robot, various versions existed,
and any program could be stopped and saved
to  certain  media. The disadvantage, just
as  with snapshotting on PCs, was that the
randomness  of  certain  programs could be
affected.  The  Multiface 1 is emulated by
SpecEm,  and  Z80  emulates  the Multiface
128. Some disk interfaces, notably the MGT
ones,   included   an  NMI  button,  which
allowed    built-in    snapshot   creation
software to run.

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TECHNICAL NEWS

Following   the  release  in  issue  2  of
SpecTest,  version 2.95, a new feature has
been  added,  and  a  bug  in  one  of the
machine  code  routines corrected. Version
3.0  is  included with this issue. It will
now  test  all  memory  above  16K  on the
Sinclair 128 and Amstrad's +2. In order to
make  the  program  remain compatible with
16K  systems,  and those with microdrives,
the  BASIC  part has been modified to take
up less memory.

Technical  editor,  Phil  Reynolds, can be
emailed:   phil@hedgford.demon.co.uk,   or
faxed: (+44/0) 1543 428082.

Technical   queries   will   generally  be
answered   in   the   following  issue  of
Emulate.

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