XiAleste Next is an 8-bit home computer, which is compatible with software for the Amstrad CPC6128 released on 13 June 1985

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XiAleste is an 8-bit home computer, which is compatible with software and hardware for the 1985 Amstrad CPC6128. It also has enhanced capabilities. It is intended to appeal to retrocomputing enthusiasts and to anybody who like to build yourself a hardware unit.

The Concept

The concept of the project was based on the idea of a new version of Amstrad CPC6128 computer - using modern components and up-to-date technology. Subsequently, this concept underwent a number of significant changes. One of these changes was the idea to equip this clone with Aleste extensions.

For reference: Aleste 520EX (A520) - is a Russian clone of Amstrad CPC6128 computer, but with some extensions. The main advantage of this computer was its sound capabilities, which were comparable with Amiga 500. The Aleste computer could play 4-channel mod files - it had a sampler synthesizer. Among the disadvantages were the high complexity of the assembly, as well as the very rare components today. Another drawback was that the A520 had two completely incompatible Aleste and CPC modes. That is all cool features of A520 were not available for CPC programs. This was the flaw that I needed to fix first.

Re-reading the book may surprise you with interesting details. But your new interpretations can be even more interesting and dramatically different from previous ones. Along the way, the project changed and its final formula for the new computer, which is called XiAleste, became the following:

  • XiAleste is primarily an Amstrad CPC with extensions available to it from the A520.
  • The A520 extensions will be redesigned -- the spirit of the A520 will remain.
  • XiAleste is 100% open source. All source files of the project will be published on github.

The XiAleste computer is a sound synthesis platform which cannot be fully emulated on an FPGA, i.e. a MIST or MISTER type board. This computer will have its own unique architecture. This architecture will have:

  • A bus for extension boards -- primary for digital peripherals devices.
  • A basic sound synthesizer system that can be extended. 
  • Bus for sound extensions -- analog sound processing modules. 

The project is very ambitious and I can not give a 100% guarantee for its quick and complete completion. But if there are people who want to get involved and help, chances are better. 

The Spirit of Aleste

This is a retro computer project, so all changes must be made with great love and respect for the engineers who created the amazing Amsrad CPC6128 computer. 

One of the major extensions of the Aleste is the MagicSound sound card. You could say it is the cornerstone of the project. Having a board of this class requires many more signals on the extension connector - more than on the CPC6128 connector. These signals are used for direct access to the memory located on the motherboard. It is important to note that the ability to access the entire address space of the computer at will is another distinguishing feature of the A520.  Although it is not necessary if the sound system is located on the processor board. Nevertheless, the improved expansion slot is something valuable to realize. 

Precisely because this connector is not known to be CPC6128 compliant it can be radically modified. There are also no plans for compatibility with the A520.

Amstrad Expansion Bus

I chose the ITX (DTX) standard as the printed circuit board design. Along the way I noticed that the original Amstrad CPC6128 connector can only be placed on the right side of the PCB. So, unfortunately, I have to give it up. But you can modify the board design and return it to the system.

XiAleste Expansion Bus

The Amstrad CPC6128 connector can be classified as a Processor Direct Connector (PDC), and the Aleste expansion connector can also be classified as such. I plan to evolve this connector to an 8-bit parallel computer bus and install two or three sockets on the board. The Amstrad CPC6128 connector for hardware compatibility can be put on the board as the same PDC without any changes.

Memory Map

Another important feature of Aleste is the use of MSX Mapper as a memory manager. However, this has been done with certain limitations. The fact is that the highest two bits of data in the Gate Array...

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The main board schematic

Adobe Portable Document Format - 6.02 MB - 01/08/2023 at 11:54


  • A minute of Fun

    h2w01/10/2023 at 13:58 0 comments

    The AI picture on the word "XiAleste" produce a cute miniature.

    The AI's random art based on XiAleste PCB image.

  • The files now on the GitHub

    h2w01/08/2023 at 11:56 0 comments

    The PCB project files uploaded to github repository

  • The voice board dimentions

    h2w01/07/2023 at 17:21 0 comments

    The voice board profile is about 35mm height.

  • Steiner Parker Issue

    h2w01/07/2023 at 11:08 0 comments

    For some reason the Steiner Parker has different slopes. Left one is 12db/oct the right one is 6db/oct. Could be something wrong with my model.

  • Steiner-Parker VCF

    h2w01/06/2023 at 18:42 0 comments

    This filter in my opinion makes the best result. With 12db per octave it makes very nice and predictable result (see image below). Love it! And the circuit is simple! 

  • The State Variable Filter is good option

    h2w01/06/2023 at 14:36 0 comments

    This type of filter looks simple enough (so it match to XiAleste project) and very stable result. The image below has all filter modes LP,BP,HP. The coice board will mix those results in different proportions.

  • Why not Moog Ladder filter?

    h2w01/06/2023 at 14:22 0 comments

    The Ladder showed worst result compare with other filters.

    BTW The way to analyze the Ladder and derivatives explained here

    What I do not like most? There are several things:

    1) Changing the output level with different resonance setting
    2) The ladder requires precise parts and tuning.
    3) The phase graph is extremely clucky. It could be something wrong with my circuit yet.

  • The voice board design

    h2w01/06/2023 at 12:25 0 comments

    About 3 weeks I have been working on a Voice board for this platform. The computer could produce sound w/o those boards, but with the boards the sound quality should go to semipro level. 

    I am doing this task now to confirm the voice board connector pinout before I will produce one unit.  

    The voice board is basically VCF. Each board has two of them. So as result 3 boards will have 6  separated channels. The board's output will goes to the mixer and also to the ADC for additional post processing (such as delay, chorus, reverb etc). 

    Currently I tried the next VCF circuits:

    1 The state variable filter
    2 Steiner Parker 
    3 Moog's ladder

    The first two give a best result and I am deciding now -- should I put bought of them on the voice board. But in case if not, which one of them should I use.

  • PCB is almost ready for manufacturing

    h2w12/17/2022 at 16:34 0 comments

    The printed circuit board is ready. Now I need to think about what to do next with this project. So far no one has joined the project. It would be too presumptuous for me to continue on my own. 

    Anyway, I will post the source files on github shortly.  

  • FMC Bus - The Length Matching

    h2w12/17/2022 at 08:34 0 comments

    5mm Tolerance 

View all 24 project logs

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h2w wrote 01/10/2023 at 18:35 point

In principle, this is interesting because KiCad makes the project more friendly to the OpenSource community. But it is embarrassing that this board has not been produced and tested, which creates a feeling of prematureness. Nevertheless, I suggest you decide for yourself.

With great respect,

  Are you sure? yes | no

paulvdh wrote 01/10/2023 at 16:17 point

If there is any interest in converting this to KiCad, then I can do a conversion (takes 10 minutes or so) and some cleanup (KiCad needs global or hierarchical labels to link between different sheets and more). Cleanup may take an hour or two, depending on how well the conversion goes.

  Are you sure? yes | no

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