The Fourth Generation of a Classic
+++ Product discontinued, please see
Catweasel Mk4plus +++
Many improvements have been made compared to the
that can be summarized under the headline 'bigger, better,
The most obvious change is the size of the card: With only 2.5
inch (63.5 mm) height, it complies to the low-profile PCI standard
that not only fits into any normal computer case, but also in
flat models that are so famous among so-called 'case-modders'.
The Flipper-interface will not be continued. Those who need a
Catweasel for their classic Amiga can use the Catweasel Z-II
S-Class, which is still availble.
Improvements to the floppy controller
While the old Catweasel models always had their own floppy drives
that were installed in addition to the existing controller and
drives, the MK4 has the option of using the existing diskdrives.
After the machine has started, the drives can be used just like
before, and after the drivers have been loaded, the Catweasel can
take control of these drives when necessary. This is especially
useful for smaller cases with fewer drive bays. This was already
addressed with previous Catweasel models, but needed an additional
product called 'Kylwalda'.
Support for auto-eject drives
Drives without eject-button are well-known from Macintosh
computers, and they're now fully supported by the Catweasel. You
can also mix floppy types, one with an eject-button, and another
from the Macintosh world on the same cable.
Hard-sectored disks supported
This kind of 5.25 and 8 inch disks were already readable with the
previous Catweasel models, but writing was only possible with a
high software effort, and it required a realtime operating
system. This effort is not necessary any more with the new
controller, because new options allow complete support of these
disk types in hardware.
Contrary to it's predecessors, the new Catweasel MK4 can pass the
data that it is currently reading from a disk to the computer
while the read access is running. This allows realtime emulation,
and error-free function of copy-protected software on
More flexible read- and write operations
In addition to working on whole tracks, which made all previous
Catweasel models so flexible, tracks can now also be partially
accessed very precisely. Should this become necessary for
compatibility or speed reasons, the Catweasel MK4 is perfectly
Although most operating systems already offer timer-functions in
software, you cannot always rely on them. The most recent example
are the timing-problems that occur with Hyperthreading-processors
and Windows operating systems. Since all timers are running
independantly in the hardware of the Catweasel MK4, nothing can
go wrong in this regard.
All events can trigger an interrupt (IRQ)
Together with the hardware-timer functions, this is the best
solution for multitasking operating systems. The driver software
does not have to check regularly if the controller needs
attention, which reduces the processor load.
Improvements to the keyboard interface
In addition to Amiga-keyboards, PS/2 devices can now also be
connected. Not only keyboards, but also PS/2 mice are supported.
The keyboard controller can now trigger IRQs, and for those
customers who want to continue using their favourite combination
of PS/2 mouse and keyboard on USB-only computers, the Catweasel
MK4 has two connectors of this kind.
Improvements to the joystick ports
Amiga mice only have minimal electronics that always pass the
movements of the device to the computer in realtime. Classic
Amiga computers have hardware-support for interpretation of these
signals in the chipset, and this support has now been added to
the Catweasel. Theoretically, using Amiga mice was already
possible with the Catweasel MK3, but this required a software
effort that was not justifiable. With the new hardware, the
software effort is reduced to a minimum.
Every signal can be programmed as output
The digital joystick ports of the 8-bit computers of the 80s were
mostly usable in two directions, they were not only inputs, but
also programmable as data outputs. The Catweasel Mk4 follows this
Compatible with CD32 pads
The game controllers of the Amiga CD32 can now also be used on
the Catweasel. A special capability of the classic Amigas (and
therefore also of the CD32) made these pads exclusive to this
computer, if connected to other computers, not all buttons of the
pad could be used. Technically speaking: Even the
potentiometer-pins of the digital joystick ports can be
programmed as outputs on the Catweasel MK4.
Improvements to the SID audio part
On the Catweasel MK3, it was possible that noises from
3D-graphics cards or high-speed harddrives were coupled into the
12V-power supply of the SID audio part. This cannot happen any
more on the Catweasel MK4, because a DC-DC converter is an
insuperable obstacle for such noises.
In addition to the known programming that's compatible with the
Catweasel MK3, the MK4 has a sophisticated script-language for
SID control. This lets the programmer define the exact time for
data to be written to the SID chips. To make sample playback
sound exactly like on a real C64, the data rate to the SID chip
must be kept at a constant rate. This is accomplished with a Fifo
memory that is big enough to maintain the datarate even under
high processor load conditions.
Digiboost for new SID versions
As opposed to the 'classic SID' 6581, the newer SID-chips 8580
and 6582 cannot playback samples any more. This option, which is
also called 'the fourth voice', is replaced by two sigma-delta
converters on the Catweasel MK4, so the fourth channel is also
audible with the newer SID versions. Since the filter properties
and the sound of mixed waveforms of all SID versions have their
supporters, this should make the decision for the right chip a
Filter capacitors selectable
Commodore has defined three different capacitor values for the
filters of the SIDs during the years that this chip has been
produced. The result was that the same chip sounded differently
if used in different computers. To bring the sound as close as
possible to what you are used to, the filter capacitors can be
chosen with a few jumpers.
The Catweasel MK3 used the commodore-chip 8701 to recreate the
exact same clock. Since the stock of this chip is empty with the
Catweasel MK3 being sold out, we have cloned it on the main logic
chip of the Catweasel MK4: The exact base frequency is generated
with crystals that have been made especially for us. By division
and multiplication according to the specifications of the C64
schematics from 1982, we managed to replace the 8701, which is
not made any more. Even the slight difference between PAL and
NTSC computers is software-selectable!
Two SIDs for stereo sound
You'll have twice the SID pleasure after installing a second SID
chip. Every SID has it's own selection of filter capacitors, and
SIDs of all versions can be mixed.
Even though PC boards with 3.3V PCI slots are not yet widely
available, the Catweasel is prepared for it. The roadmap of the
PCI special interest group plans to abandon 5V PCI slots within
forseeable time, and the Catweasel is perfectly suited for that
date. Local generation of the 3.3V power also ensures proper
function on early PCI motherboards that do not comply to the ATX
Two DMA interfaces
In addition to processor-based data transfer, the Catweasel MK4
can exchange data with the main system through two low-speed DMA
channels: The first goes throught he PCI slot, and it has a
capacity of about 8K per second and direction. The second uses
the direct connection to the onboard-floppy controller, and the
speed is up to 100K per second.
Low power consumption
The Catweasel MK4 makes use of the latest FPGA technology with
2.5V core voltage. This reduces the power consumption of the new
controller to a fraction of what the Catweasel MK3 used. This
also reduces heat generation a lot.
The FPGA on the Catweasel MK4 is completely re-configurable by
the drivers. This means that a hardware update can be done
through the internet! Should we find a disk format that cannot be
handled with the current hardware, the core of the Catweasel can
be 're-wired' to address the problem. The controller doesn't even
have to be taken out of the computer for the update!