MEGA65 FORUM

Prototype PCB!

append delete ordyne

Excellent to see this!

http://c65gs.blogspot.co.uk/2017/06/my-mega65-prototype-pcb-has-emerged.html

Does there need to be any more hardware testers for this/rev 2 ? :D

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append delete #1. PGSmobile

We can all only wish ;) There will be no more of this revision board, however. Its sole purpose is to help refine the design for the next revision.

#2. Pcbindex

This post was deleted by a moderator

append delete #3. Freddy Champagne

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.
;-)

append delete #4. LGB

I guess it was just a context sensitive spam, if a page has something to say about "PCB" and there is possibility to comment on that page, it will do automatically ;-P I see the very same msg in various forum/etc sites, without even being on-topic, just someone mentioned the word "PCB" in one post :)

append delete #5. Chris02

I'm disappointed that the board will not have sockets for SID chips. Seems kind of silly to make an add on cartridge.

Chris

append delete #6. PGSmobile

The reason is simply one of cost: to add enough area for the board will increase the cost of every board a lot, as the board is 6-layer. Much cheaper to make a simple 2-layer PCB for an add on cartridge.

Paul

append delete #7. Solei

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.

append delete #8. LGB

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 ...

append delete #9. Chris02

Could you make the PCB board larger and cut down on some of the layers?

append delete #10. gardners

No, the problem is the FPGA has a zillion pins that all need to get out of the traffic jam that is the 300+ pin BGA connector.

append delete #11. gardners

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.

append delete #12. LGB

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.

append delete #13. Freddy Champagne

OPL Chip would be nice. And MIDI-Support. But in my opinion that belongs on a (Userport/Expantionport ?) Cartridge as an optional extention.
Simply because the amount of users who really want/need this are not as many as some might think.

append delete #14. LGB

@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.

append delete #15. Freddy Champagne

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.

append delete #16. PGSmobile

No RTC at the moment. I agree it would be a nice addition.

append delete #17. gardners

Yes, there is a lot of "magic" to do this right. We have some great folks who are very skilled in this area working on it. We have also had a bit of a look at some RTC options. It isn't yet certain if one will make it into the design however.

append delete #18. ryy

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?

append delete #19. gardners

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.

append delete #20. Bascore

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 ?

append delete #21. gardners

Hello,

We use an Artix7 T100, which is about 2/3 full.
We are going to use HyperRAM instead of SDRAM/DDRAM, in part because the interface is bucket loads simpler to implement. Size will be 8MB. Data bus is 8 bits wide, and I think it does DDR x 100MHz or so, so apart from the usual latency of any non-SRAM, the throughput should be pretty good.

Regarding the module, are you talking about on the TE0725 or on the MEGA65 computer mother board?

The MEGA65 desktop computer will have both VGA and HDMI. The first iteration of the phone will have only LCD panel and VGA out. The HDMI is connected via an HDMI driver IC, to save us the pain (and FPGA usage) of having to generate the HDMI signal ourselves.

Paul.

append delete #22. Bascore2

Hi, I meant this plug-on module (0r what it is..):
https://ctrlv.cz/F7ae

2/3 of XC7A100T, that's huge, I didn't expect this.

Would you agree and support idea that once your Mega65 becomes available it can serve also as a nice platform for MIST FPGA ?
Good for you, much more people would buy it.

(I don't expect you will make the porting and do understand your goal is to resurrect C65,
thumbs up!)

append delete #23. gardners

Hello,

That short URL didn't work for me.

Yes, the FPGA is really big. At some point we will reduce the size of our design, as it shouldn't take as much space as it does.

MIST should be totally possible to port to this machine, and while as you say, we won't be doing that, we would love to see someone else do it. The MEGA65 would make a pretty nice Amiga hardware kit, I think.

Paul.

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