Subliminal Extacy #03
01 апреля 2001

The Spectrum SE - Andy Owen Interview

The Spectrum SE

Andrew Owen speaks for Subliminal  Extacy about one of the  most
ambitious projects to hit the Speccy


- What is the Spectrum SE?

I am aiming to build a modern Z80 based computer. I expect it to
be used for everything modern x86 and PPC computers are used for
because it will be powerful enough to do it but cheap enough for
people in  even the  poorest parts  of the  world to  be able to
afford.

- Why have you chosen to base it on the Spectrum?

I got my first Spectrum in 1984. It was a Spectrum +. The manual
was crap so I taught myself BASIC by refering to the commands on
the keyboard (at last a reason for that layout). When I moved on
to an Atari ST I found it much harder to create my own  programs
and I missed that about the Spectrum.

When I got Gunter Woigk's Mac Spectacle in about 1995 (the early
version with no sound support, let alone 128K) I started writing
my  own  software again.  So,  to answer  your  question, it  is
impossible for the average user to sit down and write a  program
in one  go for  modern operating  systems. They  are simply  too
complicated. I thought, given  the number of articles  posted on
CSS, there was  a real demand  for a new  Spectrum for precisely
this reason.

- What are the major features?

Well,  you have  to think  of it  as a  new computer  that just
happens to be able to  run Spectrum software really, a  bit like
the Peters Sprinter only better.

The CPU is a Z84C00 at 21.2814 Mhz. This can be stepped down  to
3.5469 Mhz for the purposes of 100% accurate 128 mode  execution
(although there isn't actually a 128 mode). It will be  possible
to  change the  processor speed  from software  or via  a turbo
button. The software switch will be compatible with the Scorpion
if possible.

The finished  machine will  be able  to access  between 16MB and
32MB (not  yet determined).  The paging  system still  has to be
sorted  out because  of trying  to maintain  compatibility with
expanded Pentagons and Scorpions. Port 7FFD will behave  exactly
like a 128 (with D6  and D7 reserved for future  expansion). The
first four bits of  port 1FFD (D0-D3) will  act like the +3  (in
order to support  PLUS3DOS software). The  remainder will be  as
compatible with the expanded Scorpion and Pentagon as possible.

The ULA  will be  replaced with  a microcontroller  in order  to
display the screens at full speed. Standard Spectrum and  TS2068
modes  will  be supported  with  the addition  of  palettes. The
FLASH/BRIGHT bits of the attribute map will be used to specify a
CLUT of 8 colours for a  maximum of 32 colours on screen  in the
standard Spectrum mode without palette switching.

There will  be two  YM2203s in  place of  the AY  chip. They are
register compatible so existing AY stuff will work but they  are
more powerful and using  two together full digital  sound should
be possible. I  haven't decided what  to do about  covox support
since I can't get any decent info on it but if I do I may end up
emulating it via the two  YM2203s. There will also be  a GM-MIDI
chip and a  DAC. The output  will be a  16-bit stereo signal  at
44Khz.

The keyboard and mouse may be PS/2, PSX or USB depending on what
works  out cheapest.  There will  be at  least one  serial port
capable of using  a 56K modem  (for internet connection).  There
will also  be a  parallel port.  Both these  will be  driven via
dedicated hardware.  There may  also be  support for Playstation
game controllers and memory cards (128K capacity).

The first four  ROMs are mapped  in using the  +3 paging system.
There may be a fifth ROM is paged in externally using the ROM-CS
line in order to support TR-DOS.

ROM 0  contains the  BIOS. This  performs any  system tests  and
intialises  the  machine  before passing  control  on  to ROM  1
(BASIC). The advantage of this is that the RST 0 instruction can
now be used from ROM 1  to provide up to 65536 system  commands.
ROM 1 contains a version of BASIC derived from the original  48K
machine.  However,  BASIC extensions  are  stored in  ROM  0 and
called on the fly from ROM 1.

ROM 2 contains the primary disk system of the SE; PLUS3DOS. This
provides support for the majority of +3 applications and  allows
+3, CP/M, and CPC disks to be read. The ROM also contains IDEDOS
which allows  the use  of a  hard disk.  ROM 3  is empty  at the
moment    but    will    probably    end    up    containing   a
monitor/assembler/disassembler  and  snapshot tool  while  ROM 4
will eventually contain a version  of TR-DOS patched to use  the
+3's disk interface.

ROM 0 and ROM 1 can  be used independently of the other  ROMs on
modified 128 and +2 systems.

The  machine  will  also  include  full  international character
support (including  from BASIC),  42 column  text from  BASIC in
256x192 mode, 85 column text from BASIC in 512x192 mode, support
for CP/M  3.0, and  a user  sizeable RAM  disk (accessible  from
BASIC using 128 or +3 commands).

- To what  extent is it  compatible with existing  Spectrums and
clones?

Compatiblity is very important for the machine to be a  success.
It will  be PORT  compatible with  the original  Spectrum but it
will also support the enhanced video modes of the TS2068  (which
are also used by  some Pentagons), PLUS3DOS, IDEDOS,  TR-DOS (as
used on the Scorpion and Pentagon), the extended memory maps  of
the Scorpion and Pentagon.  The BASIC will support  the commands
of the  Spectrum, TK90X,  Spectrum 128  and TS2068  in one mode.
Programs written for any of these machines can be loaded in  and
RUN without modification  in the standard  mode. The BASIC  will
also support the  extensions of BASIC  64, which means  that the
graphics commands will work in 512x192 mode.

- How much has been completed so far?

Most of the work so far has been spent on debugging the original
Spectrum  BASIC  and  the   128  editor  ROM.  I've   made  some
interesting discoveries along the  way, for instance, there's  a
whole chunk of useless code in  the 128 BASIC ROM (and hence  in
the Pentagon, Scorpion,  +2, +3 and  +2A). In fact  the original
BASIC ROM can  be used with  the +3/+2A without  modification to
improve compatibility. On  the 128 and  +2 three bytes  in ROM 0
have to  be changed.  It's amazing  really. Anyway,  back to the
question.  The  BASIC  has  been  completely  debugged.  It   is
certified 100%  bug free.  It has  also been  tested extensively
with a wide range of software for compatibility and no  problems
have been found so far.

The ROM layout of the machine has been determined. The BIOS  and
BASIC extensions live in ROM 0 (I'll also put the GUI toolbox in
there if there's enough room). BASIC lives in ROM 1 (even on the
+3 test version). PLUS3DOS and IDEDOS (an extension to allow the
use of  hard disks  by Garry  Lancaster) is  in ROM  2. ROM 3 is
undecided. And I haven't decided how to implement TR-DOS support
yet. I could do it by emulation or by direct support (although I
will probably go for emulation for copyright reasons, this  will
still allow TR-DOS software from the former USSR to run  without
problems).

---
For     more     information     about     the     SE,     visit
http://www.brandnewco.org/se/.

You can also contact Andrew at aowen@brandnewco.org to subscribe
to the 'SE-mail' newsletter. 



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Темы: Игры, Программное обеспечение, Пресса, Аппаратное обеспечение, Сеть, Демосцена, Люди, Программирование

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