FAQ Update for Gen-2 aka "CX16GS" system

[TomXP411]

Earlier today, The 8-Bit Guy hosted a surprise livestream on Facebook at https://www.facebook.com/adric22/videos ... 2168512216

We have created a summary of the video here: https://x16community.github.io/faq/gs-faq.html

You can also get a link to the master FAQ page from our home page: https://www.commanderx16.com/

(Please don't ask for a repost of the video. We have not received permission to do so, and it would be Copyright infringement to do so without David's permission.)

If you have other questions, feel free to ask here. We'll try to answer based on what we know, and what we don't know, we'll try to pass along to David and Kevin.

[TomXP411]

Pictures of the board (from the livestream)

Yes, that's an HDMI port up top, next to the composite video jack. The system also has a built-in wavetable synthesizer and WiFi network interface (ESP32 running Zimodem firmware.)

The system will also feature a 65C816 CPU with 32MB of RAM, directly addressable by the CPU without relying on the $00/$A000 banking system.

Otherwise, the system should function the same as the Dev system, and already runs most R48 compatible software. It should be 100% compatible by the time it hits the market.

To read the rest, click the link in the top post.

Thanks to @Wavicle for the system component annotations.

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Gen1_2_side_by_side.png (2.88 MiB) Viewed 7807 times

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[Ed Minchau]

Wow, what a great way to get people to stop doing all software development for the x16. Don't bother writing 6502 code, because that's going to be obsolete. And don't bother writing code for this new machine either, because you're going to do the same thing you did with the x16: make breaking changes every few months putting everyone back at square 1 again over and over.

I have spent the last year rewriting the METAL editor to accommodate the addition of 65816 support, so I can get back to writing the Surreal game engine and my other game, Asteroid Commander. And now whoops there goes the rug from under me again, the memory layout is going to be totally different.

How about doing a freeze on the design and doing a production run? Get that first generation out there and let us have a stable environment to work on. Then wait a few years (not weeks!) before announcing a version 2, so at least a few thousand units get out there and people can develop software for a stable environment.

The reason people are still programming C64 and other retrocomputers is they can! The computer hasn't changed. The last change to the x16 was only what, a month ago?

I'm sure I'm not the only one who has been waiting for you guys to stop revising the board before purchasing. Yet you don't say "this is it, no more revisions". And why buy an x16 now? You've just turned them all into boat anchors. And why buy a gen2 if you're going to do the same thing again?

Please, for the love of God and the sanity of the programmers, stop making breaking changes! Finalize the X16 design and call the gen2 one something else entirely.

[Guybrush]

And now whoops there goes the rug from under me again, the memory layout is going to be totally different.

Have you even watched the video? David clearly stated that in 8-bit mode the memory layout will be exactly the same as in the Gen1 boards, since the FPGA that replaces all the address decoding logic can detect the mode the processor is running in and change its behavior accordingly. So, if you target only the 65C02 instruction set (minus those four(?) instruction missing from the 65C816), you'll be just fine.

If you want to use the flat memory model of the 16-bit mode then yes, you'll have to change your code, although I think it will only make it simpler since there will be less need for constant bank switching because the new "banks" will be 8 times bigger.

[mgkaiser]

Is the pinout of that card edge connector the same as the expansion slots? If so it would be possible to make a backplane and add more slots. Having said that given what has been added to the board I'm not really clear what I'd put on an add on card. 32MB directly accessible to the '816 bus makes this an AMAZING computer.

[Mkopack73]

I asked that question last night during the livestream. David didnt have a ton of info on that bus connection but did say that it was intended to be the full bus so that a breakout backplane could be made to support additional cards later. The central slot is the same as the existing gen 1 slots as it will be used for cartridges (they are going for the gaming console motif with this one).

Whether the bus connector is the same pinout or different wasn’t clear/known though.

[DragWx]

There are now three platforms; from greatest to least compatibility:

• 65c02 (with 65c816-incompatible opcodes avoided)
• 16-bit-addressed 65c816 (upgraded Gen 1, PB/DB registers don't work, bankswitched ram only)
• 24-bit-addressed 65c816 (Gen 2/GS, PB/DB registers work)

In other words, this is more like an Amiga where everyone has the same base featureset, but can have a different configuration, different accelerators, etc, with the GS now being a standardized configuration, rather than a C64 where every computer is identical.

The GS having working PB/DB registers was the only thing I wasn't expecting (but it's pretty exciting since that's a big advantage the 65c816 has).

[mgkaiser]

I just did the math. How are we addressing 32MB of RAM on a 24bit address bus?

[m00dawg]

I just did the math. How are we addressing 32MB of RAM on a 24bit address bus?

It's in the FAQ Tom linked earlier but in brief:

2MB at $00/$A000 banks will still be available
16MB will be available when in 16-bit mode
Some sort of ROM mapping will also be possible. (See Kevin’s notes below.)
BASIC RAM likely still limited to 37KB, with I/O at $9F00-$9FFF

The ROM mapping bit is one of the proposed features of the extra 16MB (copying the KERNAL ROM into RAM, e.g.) but there are other potential use cases though these may be for system related things and not for direct user access.

[mgkaiser]

How about a C compiler? CC65 has limited support for 65816. Calypsi has pretty good support and already has profiles for the Foenix256. Should be a pretty short lift to get CX16GS support into that. Finally it is possible to write relocatable code on the 65816. I don't think Calypsi does that. Does anybody know of a C compiler that does relocatable 65816 code?