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Catweasel MK4
Catweasel MK4 PCI
The Fourth Generation of a Classic

+++ Product discontinued, please see Catweasel Mk4plus +++

Many improvements have been made compared to the Catweasel MK3 that can be summarized under the headline 'bigger, better, faster'.

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.

Dual-ported memory
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 emulators.

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 prepared.

Extensive timer-functions
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 tradition.

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.

Cycle-exact control
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 little easier.

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.

Precise clocking
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.

Technology improvements
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 standard.

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.

Re-configurable logic
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!

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