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C65 Next Generation MEGA65

  • Yes, the keyboard development is complete. Why do you ask ?

  • Paul achieved a new level regarding compatibility.

    The MEGA65 is now almost cacle exact, but before i write much more, hop over to Paul's blog.

    Or read it here:


    (Just about) cycle-perfect PAL 50Hz HDMI video on the MEGA65

    1573816827516.JPEG

    I've put a fair bit of effort this week into getting the HDMI video output of the MEGA65 working, and together with that, to get the timing of the video modes as close as possible to perfect. This has involved a few things:



    1. Adjusting the frames to have exactly the right number of raster lines (it was out by one before).


    2. Making the video generator provide the PHI clock pulses to the CPU, so that there are always the right number per raster line. As the raster lines are not exactly the right length, this introduces a very small amount of jitter in the cycle durations. However, this will average out to zero over a few raster lines, and so shouldn't produce any audio artefacts.

    3. Lots of other miscellaneous fixes.



    Anyway, combined with the nice 4:3 digital output via the HDMI port, this means we are now creeping towards a really nice level of compatibility for display timing. Some tricks, like VSP, are unlikely to ever be supported by the MEGA65's default FPGA core, but lots of other things should work well now, including most sprite multiplexors etc.



    There are still a few rough edges to sort out, in particular there is a bug in the VIC-IV that is preventing it from numbering raster lines in the flyback properly. This stuffs up some raster interrupts etc, and will get fixed fairly quickly, I expect.



    In fact, the video and CPU timing are now just about good enough to run the freeze-combined.prg test from the VICE emulator test suite. This nasty little program runs interrupts on both CIAs which are used to draw green and yellow raster bars. A separate raster interrupt runs, which draws a red raster bar. The yellow and green raster bars have accompanying bars drawn in the active part of the display, and to which they should stay lined up. This requires that the CIAs correctly count down, and that each video frame has exactly the right number of cycles, so that they don't drift up or down between frames. And that all now works on the MEGA65 :)



    The only part that doesn't, is the grey and pink bars in the active part of the display creep upwards, indicating that the CPU is running slightly faster than it should. This is almost certainly because the MEGA65 always charges 40 clock cycles for a bad line, instead of between 40 and 43 as on the C64. Apart from making this display creep, it is unlikely to be a problem for most programs, as the timing is within 1%, and slightly fast rather than slow.



    And finally, since the whole point of this test is to be able to demonstrate freezing and unfreezing without messing up the CIA to VIC to CPU synchronisation, I had a bit of a poke around to fix this. Basically I need to make the freezer always trigger on a fixed raster line, and then have the unfreezer always wait until that raster line before resuming the frozen program. In theory, that should be enough to restore the synchronisation to within a couple of clock cycles. To get an idea of how it should behave, and how it (usually) behaves right now, here is a short video I made:




    Fixing this synchronisation will have to wait for another post.

  • Hello ladies and gentlemen,


    we would like to announce, that the MEGA65 team is taking a break for the christmas season and that we will be

    back with full steam in apprx. 2 weeks.

    the other team members and i will still pass by here and will answer, but not as regulary as normal.

    My and the teams goal for the next two weeks will be simply, to spend some quality time with our beloved ones.


    With this said, the MEGA65 team would like to wish all of you a merry christmas and all the best for 2020.

    we will be back in the new year to continue to work on the last great 8-bitter !


    :weihnachten:

  • Hi all and a happy new Year !!!


    even if not officially back from the Christmas break, but since Paul was here in germany for the Leipzig conference,

    they couldn't resist, starting to work on the MEGA65.


    The most important thing, Paul is looking for a way to update the MEGA65 bitstream, without the need of an external flashing software and to create a kind of boot-up-bitstream-selector.... There are several precautions he has to take into account, to prevent bricking our beloved MEGA65. This sounds very nice !

    Read more about his progression in his first Blogpost for 2020 here


    For the second update, we did a bootup-time comparison between the MEGA65 and the THE64 Maxi.

    Paul states in this short video and i want to do the same here, that we do like the THE64 maxi, but i think it might be interesting for several people, to see the difference between an emulation and real hardware.

    You can find the video here.

  • Happy New Year! Paul should have been comparing both machines booting into C64 mode in the first place to persuade potential buyers from outside the actual community.

    Anyway this video is impressive. Looks like a very hot summer down under judging from Paul's trousers.

  • Happy New Year! Paul should have been comparing both machines booting into C64 mode in the first place to persuade potential buyers from outside the actual community.

    Anyway this video is impressive. Looks like a very hot summer down under judging from Paul's trousers.

    He he :) The short pants were actually in Germany, where it was a pleasant -2C outside. I stay in short pants down to about -15C, if there is no wind.


    Also, for those who didn't spot it, there is a German version of the boot time comparison video at:


    https://www.youtube.com/watch?v=hoiS93hXCvo


    LG

    Paul

  • Kann leider kein Englisch - sorry daher für den deutschen Text...

    Beim Stöbern auf der MEGA65 Seite kam mir gerade so ein Gedanke... (bitte etwaige Ungenauigkeiten in meiner Beschreibung mal nicht überbewerten!!)

    Es gibt den C128 - ein Rechner mit nem Z80 für CP/M intern und mit nem C64 Modus, sowie dem C128 Modus...

    Es gibt bald den MEGA65 - ein Rechner mit nem C64 Modus, nem C65 Modus und dem speziellen, modernen MEGA65 Modus - korrekt soweit?

    Dann gibts da noch den C16 und seine nahezu baugleichen Brüder...


    So RICHTIG genial wäre es doch, wenn man - VIELLEICHT abgesehen vom Z80, da zu speziell und zu aufwändig - alle der aufgeführten Rechner in einem einzigen vereinigen würde?!?
    Die meisten Dinge sind ja schon drin im MEGA65 und DIESE "Revision" auch mehr oder weniger fast fertig, aber zukünftig gibts doch sicher noch Pläne zur Optimierung und Weiterentwicklung?!?

    Wäre es zumindest technisch denn möglich, mit der HIER vorhandenen Hardware auch eine Plattform für den C128 Modus und den C16/plus/4 zu bieten??? Das "fehlt" ja im Grunde "nur" noch im aktuellen Gerät...

    Ja, ist ein Hirngespinst und passt hier nicht so ganz rein - habe aber keinen besseren Thread gefunden. Aber die Idee finde ich irgendwie schon spannend. :)

  • Machbar ist das alles. ;)


    Vergiss aber eben nicht, dass die Hauptintention von MEGA war, den C65 zu "vollenden" - DAS zu beenden, was C= nicht mehr imstande war zu tun. DEN dedizierten Nachfolger des C64 zu bauen, der es "nicht mehr geschafft hat".


    Mir imponiert das Ganze wahnsinnig. Die Vorstellung, bald diese Maschine besitzen zu können, die es im Moment nur in Bruchstücken und unvollendet für zigtausende von Euros da draußen gibt... das hat schon was.

    Einen 128er oder 16er nachzustellen ist dagegen...ja, sagen wir mal.... eher "nicht so spannende". ;)

  • ich seh das auch so, das sie erst einmal das fertig stellen was sie angefangen haben.

    einen c128 und c16 modus fänd ich aus dem einfachen grunde gut, das man nur noch

    einen computer auf dem tisch hätte. mir geht langsam der platz aus.

  • Mir imponiert das Ganze wahnsinnig. Die Vorstellung, bald diese Maschine besitzen zu können, die es im Moment nur in Bruchstücken und unvollendet für zigtausende von Euros da draußen gibt... das hat schon was.

    Geht mir genauso... würde den auch mit 'nem Billig-Gehäuse kaufen, wenn die Moulds nicht finanziert werden können.


    Einen 128er oder 16er nachzustellen ist dagegen...ja, sagen wir mal.... eher "nicht so spannende". ;)

    C128? Geh mir fort...braucht kein Mensch :whistling:;)

  • Bis auf den Z80 Modus ist der Mega65 eh ein Vielfaches des C128 und des Plus/4/C16/C116. Das Basic10 ist weiterentwickelter und vor allem ist der Mega etlich schneller.

    ___________________________________________________________________________
    Ultimate64, TAPunio, SD2IEC, ZX Spectrum 48k, 1581 Replik, C64 Laptop, C64 MK II, C116, SX64,
    MiSTer FPGA, TI99/4A mit PEB, Atari 800 XL, Anycubic I3 Mega, Mega65, C64 Modular, Uniprom64

  • Wäre es zumindest technisch denn möglich, mit der HIER vorhandenen Hardware auch eine Plattform für den C128 Modus und den C16/plus/4 zu bieten??? Das "fehlt" ja im Grunde "nur" noch im aktuellen Gerät...

    Da der MEGA65 FPGA basiert ist, ein eindeutiges: JA

    Theoretischerweise könnte man sogar den Amiga nachbauen.....