ZXNet эхоконференция «code.zx»

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* Forwarded from ZX.SPECTRUM by Kirill Frolov (500:812/9.8).
* Originally by: Stas Sergeev (2:5020/3456.28), 22 May 99 02:55.
* Originally to: All.
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Приветствую тебя, All.

Помнится, недавно тут велись споры о существовании сабжа, и было решено, что
его нет и быть не может.
Так вот, смотрите и удивляйтесь:


=== Cut ===
[Logo] The Linux/Microcontroller Project
ZILOG Z-80 Port

uClinux ported to Z-80

There has been much work by various parties to
extend the architectures supported by uClinux, and
these have included the MC68EZ328 chipset (widely
used in consumer PDAs), and Coldfire, Motorola's
next-generation embedded processor line. However,
we've been working on some internal projects that
pave the way for uClinux to operate on systems with
much tougher memory constraints. We're proud to
announce the first screen shots of a port of uClinux
to the venerable Z-80 processor.

This processor, while not especially fast, has been
used in a vast array of mass-produced computers,
making it a valuable chip to support. Previously,
it's been passed over by more mainstream operating
systems as being too inefficient or difficult to
support. We feel that it is important that Linux be
usable whereever possible, so we've spent the time
to port uClinux to support the Z-80 platform. We feel
this will benefit a wide variety of people, both in
the design of new and inexpensive computers, and as
a way of providing a useful and stable OS to the
many owners of computers already designed around
this processor.

A technical challenge

There were many stumbling blocks for producing this
port. The ZILOG Z-80 is relatively old, as processor
designs go, and being an 8-bit design is nearly one
fourth the speed of modern 32-bit processors. That,
and the fact that Z-80 systems were designed back in
the days when memory was quite expensive (even ROM,
never mind RAM), makes for a very constrained
system. We've had to use several innovative
approaches, including overlayed kernel loading
(using the XOR reduplication technique to store two
code pages in every page of ROM) and apply data
compression to RAM pages in order to get enough free
memory to boot. Despite the challenge, we have
succeeded, and would like to show you some of the
progress we've made.

[Здесь было про TRS-80 Model IV, так что skip]

uClinux running on an emulated Sinclair Spectrum

Here you can see the tail end of the boot screen of
uClinux on an emulated Sinclair Spectrum, using the
excellent xzx emulator. I apologize for there not
being much detail visible, unfortunately the
Spectrum's screen does not lend itself to displaying
large amounts of information. Again, as with the
TRS-80, there wasn't enough RAM available to start
up init and a shell. Adding more RAM should be a bit
easier then the TRS-80, although some of the
problems unique to the Spectrum (such as the memory
extension tending to wobble and fall off) may
eventually limit the utility of this platform for
running full-scale uClinux applications.

[Тут был скриншот. КРУТО!]

In times to come...

Given the fact that these demonstrations were based
on heavily modified emulators (to support the
neccessarily large amount of emulated ROM), it will
be some time before we can wrap up the changes into
something useful that can be released. We estimate
that a source code bundle of the Z-80 port will be
ready by some time after March 31st, 2000. This
planned release will include source patches, the
requisite cross-compiler kits, and if the memory
requirements are still larger then the average Z-80
systems support, a kit will be supplied including
software patches for the common emulators, and
designs for hardware modifications to allow booting
uClinux on some particular hardware designs,
probably including the TRS-80 Model III, and the
Sinclair Spectrum/128K. We hope to have ported the
Speccy classic Advanced Lawnmower Simulator over to
the uClinux/Z-80 OS by then, so that the hardware
capabilities of the Sprectrum can be fully
appreciated.

For more information

If you wish to get in touch with the uClinux
development team, please send mail to
uclinux@RyeHam.ee.ryerson.ca. Kenneth Albanowski and
Jeff Dionne are the technical leads, with Michael
Durrant providing support. This announcement was
written by the fourth member of the team (who, as
Kenneth keeps pointing out, doesn't get nearly
enough mention) and the only one that can be trusted
to write a decent annoucment, Lirpa Loof.

4,155 й Copyright April 1, 1999 The uClinux team
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Hу вот и все. Бывай, All.
-+-
+ Origin: -= Sorry, permanently under construction. =- (2:5020/3456.28)
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Hемедленно нажми на RESET, All !


Kirill Frolov. [ZX]