Commodore Free 11/Commodore_Free_Issue_11_2007_Commodore_Computer_Club.d64/t.iv jens 4

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u    Interview with Jens Schofield
         Individual Computers

 http://www.jschoenfeld.com/index.htm

PART 4 of 4

Q-Are you currently working on any-
thing new, as of yet undisclosed? And,
would you care to share? I promise to
keep it between us & a few hundred
readers.

A-I'm working on two flickerfixers,
one for the Amiga that will output a
75Hz picture for PAL screens, and
another for the C64, because I keep
losing 15kHz C64-compatible monitors.
Both products will most probably not
be finished this year [this interview
was made in 2006, the flickerfixers
are put on hold because of the very
successful contract work] Since we
agreed that this interview is not
published before October 2006, I can
also share the biggest project with
you: I'm working on the Amiga chipset,
together with Oliver Achten, the
developer of the MMC64 & now the
project leader of "Clone-A". He's one
of the two guys that I have hired since
January of this year, & we started the
plans & preparations for this project
in late October of 2005. The goal is to
create a cycle-exact Amiga chipset
replica with today's technology. Oliver
& I are going to demonstrate the proto-
type at this year's [2006] AmiWest
show. The demonstration will be some-
thing that the visitors can influence:
I'd like to encourage people to bring
their favorite disks with them & try
them in our computer. Any game, demo or
program, just bring the disk -- the
computer has 2MB chipmem & a 68000
processor. Let me emphasize again that
we are not selecting the kind of soft-
ware that will be demonstrated -- we
will be completely unprepared for the
kind of programs people bring. We just
want to demonstrate that if it runs on
an A500, it'll also run on our chipset.

The current name of the project is
"Clone-A". We're replacing each chip of
an Amiga 500 bit by bit. At this point,
Denise, Gary, Paula & the CIAs are
completely removed & replaced by small
FPGA boards. It's pretty certain that
we won't have a finished Agnus chip at
AmiWest, but we already have a very
good idea of what's inside, because we
have already reverse engineered the
inter-chip communication, & to do this
large parts of Agnus need to be known.
[update: the Clone-A chipset is
finished, including Agnus, & has been
demonstrated on march 31st, 2007].

Our approach to a re-implementation of
the chipset is surely one that takes
the longest, compared to a full
implementation "from scratch" that
Dennis van Weeren did for his Minimig.
There's also NatAmi that tries a full
re-implementation based on
documentation. Oliver & I are going
the most complicated route, but being
able to work with any combination of
the real chipset & our FPGA-replace-
ments leaves no room for mistakes. We
have no other chance than to be 100%
correct, & everytime we're fixing a
bug, we discover that the fix actually
produces a smaller design. It's really
amazing what Jay Miner & his colleagues
have crammed into about 20,000
transistors per chip! I really have no
idea when I can turn this chipset into
a product, but it gives a lot of
possibilities.
You can think of a new classic Amiga
board, an extended chipset with more
chipmem & a faster blitter, a daughter
card for whatever mainboard that you
can buy today & many other things. I'd
also be open to a cooperation with
someone who wants to turn this chipset
into a toy like the C64DTV. A portable
Amiga that runs for many hours on a
cellphone battery is definitely within
reach. [update: the first Clona-A
machines are planned for Xmas 2007].

Q-Could you elaborate a bit about the
different approaches between "Clone-A"
& the Minimig?

A-Dennis took the UAE source & the
description of the chipset registers
to make a forward- engineered Amiga-
compatible chipset. This is not neces-
sarily a bad move, but like I said, our
approach leaves no room for mistakes,
while he has much more freedom for a
similar, but not exactly-the-same
implementation. Before we take the next
step of implementing a part of a chip,
we do extensive reverse-engineering,
for example by writing test programs &
doing measurements on the chips with a
logic analyzer while the programs are
running. We also do really strange
things to find out what the inner
workings of the chips are, for example
programming them in ways that you're
not supposed to.

Q-How many man-hours have gone into
bringing it to its current state, & how
much more time do you expect will be
required before you have something
finished?

A-We never counted the hours, but the
combined manpower is easily 2000 hours,
given the fact that we're both not
working full- time on the project, &
that an average working-year has 2000
working hours. I'd say that we need
another 300 hours to bring Agnus to a
state where it can be considered cycle-
exact. [update: it took a lot more than
that...] It's really hard to tell how
much work has gone into the project,
because I have put a lot of knowledge
into it that I gathered before the
start of Clone-A. I once did an add-on
for a TV studio that wanted to have a
special Genlock interface: They not
only wanted to mask between the
computer-picture & the TV picture, but
they wanted to define a transparency
for every color that the Amiga
displays. I was only able to do that
with an almost complete implementation
of the Denise bitmap-logic, so I
already had good knowledge about Denise
back in 1995. Then Oliver did further
research for his implementation of
Denise, which has many features that
haven't been discovered yet, even by
emulators. The next thing is the part
of Paula that controls the disk drive:
There's a lot of Catweasel knowledge
that I explained to Oliver, & he
implemented the floppy part in record
time. That's another big advantage we
have: We are a team, while the other
projects are made by single people.

Q-So, let's just get this straight,
the Clone-A will basically be a
complete miniature-A500, 100% hardware
compatible, that can be offered in any
configuration you might want an A500
in today? A500-in-a-joystick, A500-in-a
desktop-case, A500-in-a-handheld, etc?

A-Anything that involves an Amiga-on-
a-chip (such as a joystick or handheld)
requires huge investments that I can't
do alone. However, our approach
compared to the forward-engineering
approach that Dennis does - produces
the smaller design, so in the end, ours
is better-suited to be produced as a
chip. If there is an investor who wants
an Amiga on a chip, Oliver & I can
offer the smallest & therefore cheapest
design with the positive side-effect
that it is cycle-accurate.

Q-Does it come with an IDE interface &
RF-modulator? Would there, by any
chance, be Catweasel technology doing
the floppy controlling?

A-I'd say that a mini-ITX Clone-A
should have everything that a classic
Amiga user has today: Halfway decent
CPU (at least an 030), IDE, floppy
that works with normal 1.44Mb drives &
a PC keyboard & mouse connector. The
monitor should be VGA, not an RF
modulator. There's a good demand for
A1200 boards, but supply is limited &
the prices are high. However, anything
that I'm dreaming of here should be
taken as what it is: Speculation. I
don't know what the final specs will
be, nothing is written in stone yet.

Q-How do you anticipate products
incorporating Clone-A being marketed?
What will the first revision be able
to do, & what can be expected from
future revisions? Will there some day
be a "Clone-B" emulating the AGA
chipset?

A-AGA does not add very much to the
design size. Since the blitter & the
complete Paula chip stayed the same,
we're only talking about 27 instead of
25 DMA channels & a local bus
performance upgrade by a factor of 4.
That's something we can easily
accomplish with the type of memory &
the type of logic chips that we're
using. Remember that we're talking
about a machine that was up-to-date in
1985. According to Moore's law, AGA
performance should have been reached
36 months later in 1988. We are using
2007 FPGA technology, where talking to
133MHz SD-Ram is no trouble at all.

Q-If a new revision would at some
point be released, would the original
Clone-A be upgradable by a quick
reflash of the FPGAs?

A-Yes, as I said earlier, I'll try to
keep all my future hardware recon-
figurable.

Q-Will it come with an "Amiga OS & ROM"
licence, making it a complete A500/2000
once you add the basic peripherals? Or
could it be bundled with Amiga Forever?

A-That's what I tried to discuss with
Bill McEwen, but he failed to prove
that Ainc. is the rightful owner of the
Amiga IP over almost two years now.
There are more options, because there
are multiple authors who made Kickstart
replacements for the Amiga1000 back in
the days, & I managed to dig up two of
those authors. However, a true name
license from the big brand of the 80s
is the most desirable option, & that's
work in progress; nothing to repport at
the moment.

Q-Have you been in discussion with any-
one else about turning this into any
specific type of mass market product?

A-Sure, but no written agreement has
been signed yet, so I would not like to
give their names here.I don't expect
that it's reasonable for all the good
boys & girls out there to expect Santa
to bring them one of these this year?

[2006 answer] No chance, sorry. As I
said, Agnus still needs a lot of work,
& after that, we still have to
implement a 68000 processor into an
FPGA before an Amiga-on-a-chip can be
made. I even doubt that Santa will make
it in 2007, but you never know. The
worst thing that can happen to a hard-
ware design is that the news about the
prototype is spread too soon. If
Minimig & NatAmi would not exist, I
would not be demonstrating Clone-A at
AmiWest this year, I would rather wait
until the first product with the
results of the work is ready to ship.
Most people don't realize that a
working prototype only makes perhaps
30% of a finished product.

[2007 update] Oliver & I are working
hard on Clone-A so the first version
can be shipped this year. However,
Clone-A is still no finished product &
the only thing I can ask for is
patience.

Q-Lastly, anything else you would like
to add?

A-This has gotten really extensive. I
hope not boring. Thanks for everybody's
time!