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Prototype PCB!

  • Whether it's in the manufacturing or assembly process, or in http://www.pcbindex.com/practical applications, custom PCBs must have reliable performance. In addition to increasing costs, defects in the assembly process can be brought along with the PCB to the end product, which can lead to failures in practical applications and lead to claims for sale. Therefore, it is no exaggeration to say that the cost of a high-quality PCB is negligible in this respect.

    In the market segment, especially the manufacturing product market applied in key areas, the impact of such failure is unthinkable. Therefore, the above points should be kept in mind when comparing PCB prices. Although reliable, the initial cost of a guaranteed and long-lived product is high, it is indeed worth it in the long run.

    I just ran the chinese post trough translater, so people can quickly understand Pcbindex's posting.

  • I have probably mentioned it before - but why not make a simple dual layer daughtherboard to accommodate just the sid chips and filter caps, connected to the motherboard internally with a flat cable?

    There is more than enough space inside the machine for it to fit - and this solution could also be supplied as a diy kit with standard through-hole components.

  • I'm not sure it would work, but since M65 will have cartridge port, and exactly that is suggested to be used for a "real" SID cartridge, it would be easy to provide an internal pin-header near the part of the PCB where the cartridge port is provided. So as @Solei suggested, it would be easy to provide an internal "cartridge" this way (ie, a daughter board) optionally (or even by default) fitted, without the need to design an very complex PCB to have these "add-ons" on the main PCB. Also, it wouldn't block the cartridge port from other devices, which can/could be the case if an external SID cartridge is plugged in, but some other cartridge wanted to be used as well ...

  • Solei: What you are proposing is simply an internal cartridge, as LGB has also indicated. My understanding is that adding even the area for another internal connector is a problem, in part because there are lines going through all those layers all over the place, and pushing them all out the way of a large space for a connector would be non-trivial. If you were truly desperate to house the SIDs internally, it would probably be possible to do something horrible using the internal 34-pin floppy connector, as it has enough 5V lines.

  • Well, yes, a multiple layer board is nightmare even if you add an extra component somewhere because of its nature. I only suggested the internal pin header, as somehow the external cartridge connector must be connected to the PCB anyway, so it's maybe easier to provide an internal pin header very near to that point. All other places / solutions would require re-route the PCB design and maybe using more layers, as far as I can imagine the situation, though I have never seen the whole schematics of the M65 and/or board design at all ...

    :: @LGB added on 05 May ’18 · 17:02

    Also, adding an "internal cartridge pin header" would allow some personalization of adding always-used external hardware to the system, in the form of "external yeah, but well, internal to the case" :-P I would opt to try an SFX Sound Expander, home made, the OPL chip only, for example, as en extra.

  • @Freddy Champagne Yes, I said exactly this, an optional "internal cartridge expansion pin header". Surely, it's an optional internal "daugtherboard". But can be used for "real SID" PCB as well, since then probably a single layer/side little PCB is enough as well with a SID socket is enough, and it's extra cheap then rather than re-designing a 6/8 layer main PCB to have SID socket as well. And as a bonus it can be other PCBs as well like with that OPL, if someone wants, but not for everyone, as you also noticed.

  • Btw.: does the MEGA65 have an buffered RTC onboard?
    If not: would it be difficult to add the cassette-port on Board Rev. II or the MEGA 'AT' ;)
    Because in my opinion, that port is not so useless as CBM tought. They used it only for tapes, but in real life there were many add-ons that used the cassette-port, especialy using i2c system, for RTC, and temperature-sensors, or similar.

  • Read on the blog about the MEGAphone using the Trenz TE0725 FPGA module instead of FPGA soldered to PCB, which sounds like a good idea. Is this approach considered for the regular Mega65 as well? Would that not allow the main PCB to be double sided and much cheaper? Then it would be a no-brainer to include the dual SID sockets (with 9/12v jumpers) which I think should be default on any remake.. A/Ds inserting the SIDs audio into HDMI stream is even better. At one point it was mentioned that there might be a source for NOS SID chips for the Mega65, is this still the case?

    It is very cool that you guys are creating a complete package, very interesting to read about the progress and challenges, just concerned that it is turning into a more hands off sealed box, instead of hardware to tinker with, internal headers/sockets (or solder points) etc that's part of the fun.

    Is the original Nexys4 FPGA board the elephant in the room? Is it adding extra complexity and raising the price? Would a cheaper FPGA with less pins (even QFP for serviceability) with external RAM be a simpler and quicker hardware solution with the decoupled core? I guess BGA on a module would at least keep rest of system simpler.

    Not to detract too much from this thread, but is the core being tested with C64 demos to ensure VIC-II (timing) compatibility?

  • So for the desktop computer, the TE0725 isn't really an option, because there just aren't enough pins free for everything: Just the VGA output and expansion ports alone would use them all up. Then we have keyboard, the internal expansion connectors etc. Routing would also require at least 6 layers (which we know from laying out the hand-held/phone version as part of the student projects), so the board would not be any cheaper to make. It really is just easier (and cheaper in practice) to have one fully integrated board.

    As for it being a "hands off sealed box", this will not be the case. There will be a number of standard PMOD connectors internally that will make expansion and tinkering quite possible. Also the cartridge port allows for much more sophisticated cartridges than on the C64.

    For compatibility, we are not yet at the point of running demos to test. There are a few reasons for this. First, the C65 basically can't run any demos, because of the CPU instruction differences and signfiicant timing differences in the VIC-III. That said, we are working to improve the compatibility as much as is practicable. I'll likely post a blog post soon describing the real-time debug facilities I have added that let us monitor the instruction stream and significant VIC-IV events, such as raster line advancing and triggering of badlines. 100% C64 compatibility is not our primary goal at this point in time, only "good enough" compatability, so that we can get it out the door and into your hands. "Good enough" to me, means that it can run most games and GEOS without significant problems. But as it is FPGA based, nothing will stop us (or you the community!) working either improving the C64 compatibility, or making a dedicated C64 bitstream to deliver 100% compatibility.

  • I am curious about what is on this board.
    Could you (Paul) state current FPGA type you work with & how full it is ?
    Is there any SDRAM/DDRAM connected to the FPGA ? What size & bus width ?
    What is the module in bottom-left corner ?

    You mentioned VGA connector, does it mean there is no HDMI output
    or are there both ?
    If HDMI is contained, is it generated directly by FPGA or do you use any specialised IC ?