FPGA vs Real, what is the tradeoff?

[paulscottrobson]

5 hours ago, BruceMcF said:

As far as parallel connection which allows add on CPUs to use the hardware, that's one thing the CX16 has, though there isn't any hand holding on the bus mastering.

It's more of a very fast parallel I/O system than a CPU socket.

[paulscottrobson]

2 hours ago, ZeroByte said:

The whole "It's just a PET with a VERA" argument is kind of unfair.



The NES is just an Atari VCS with a PPU and APU glued onto it.

The Atari 800 is just an Apple 1 with a video chip glued onto it.

Etc.

Let's face it - from the perspective of anyone who played games or made / watched demos, the things that give the systems their unique character ARE the video and sound chips. They pretty much all had some kind of data ports, etc and peripherals were available or not, had different UIs and whatnot, but they're all essentially a 64K address space driven by a 6502, and having some assortment of peripheral ICs mapped into this space by glue logic on the bus.

What defines the CX16 and the others. For the NES it's the PPU/APU. For the Atari's it's POKEY and the other chips. For the CX16 it's Vera. I have no problem with that. What's comical is that it's some sort of authentic retro design. All it does is scale the price by a factor of 3 or 4.

[BruceMcF]

20 hours ago, paulscottrobson said:

It's more of a very fast parallel I/O system than a CPU socket.

The expansion cards include the lines to allow a card to take over the entire bus and access anything on the bus, which is much more than "a very fast parallel I/O system".

Quote

What defines the CX16 and the others. For the NES it's the PPU/APU. For the Atari's it's POKEY and the other chips. For the CX16 it's Vera. I have no problem with that. What's comical is that it's some sort of authentic retro design. All it does is scale the price by a factor of 3 or 4.

So it seems you are saying you are in the CX16e market, not the CX16p or CX16c market, and are also sharing with us that it strikes you as comical to be in the CX16p or CX16c markets.

That would explain why from your perspective "all it does" to have the kit-buildable system reference design is to scale the price by a factor of 3 or 4 (and by extension, "all it does" to have all the core 8bit components but in surface mount where available (and with other cost cutting design steps like fixed RAM soldered on the board or only one expansion port) is scale the price by a factor of 2 or 3).

It's an entirely subjective matter whether or not the design of the Vera is or is not a "next best thing" to the 8-bit style VGA graphic chip that is not on the market from the perspective of fitting appropriately into a system made with 8bit CPU, peripheral chips, ROM and RAM and glue logic. People can share their views and why they have them, but it's not like a technical question with an objectively correct answer.

The objective dimension is that the subjective views that are really relevant to the question are the people who are in the CX16p and CX16c markets, since they are the only people whose views on the subject have a direct impact on whether they want to buy into the project.

It's fine if our views on the subject are viewed as comical by those who don't care about the question, precisely because those people don't really care about the question, and they will buy into or not buy into the project for different reasons.

[StephenHorn]

11 hours ago, BruceMcF said:

The expansion cards include the lines to allow a card to take over the entire bus and access anything on the bus, which is much more than "a very fast parallel I/O system".



So it seems you are saying you are in the CX16e market, not the CX16p or CX16c market, and are also sharing with us that it strikes you as comical to be in the CX16p or CX16c markets.



That would explain why from your perspective "all it does" to have the kit-buildable system reference design is to scale the price by a factor of 3 or 4 (and by extension, "all it does" to have all the core 8bit components but in surface mount where available )and with other cost cutting design steps like fixed RAM soldered on the board or only one expansion port) is scale the price by a factor of 2 or 3.



It's an entirely subjective matter whether or not the design of the Vera is or is not a "next best thing" to the 8-bit style VGA graphic chip that is not on the market from the perspective of fitting appropriately into a system made with 8bit CPU, peripheral chips, ROM and RAM and glue logic. People can share their views and why they have them, but it's not like a technical question with an objectively correct answer.



The objective dimension is that the subjective views that are really relevant to the question are the people who are in the CX16p and CX16c markets, since they are the only people whose views on the subject have a direct impact on whether they want to buy into the project.



It's fine if our views on the subject are viewed as comical by those who don't care about the question, precisely because those people don't really care about the question, and they will buy into or not buy into the project for different reasons.

I found parts of that to be a little hard to parse, but I think I pretty much agree. Honestly, I have my doubts as to whether Paul will ever buy even the X16e, because the emulator is even less expensive and provides all the features of the X16 at an acceptable level of performance. With a little tweaking of the source code, it could even emulate the CPU (and various other components) running even faster than the real X16 will allow. I don't think Paul has ever indicated what, exactly, is interesting to him about the X16.

[BruceMcF]

46 minutes ago, StephenHorn said:

I found parts of that to be a little hard to parse, but I think I pretty much agree. Honestly, I have my doubts as to whether Paul will ever buy even the X16e, because the emulator is even less expensive and provides all the features of the X16 at an acceptable level of performance. With a little tweaking of the source code, it could even emulate the CPU (and various other components) running even faster than the real X16 will allow. I don't think Paul has ever indicated what, exactly, is interesting to him about the X16.

A compiler would have simply abandoned parsing, as it had unbalanced parentheses, just recently fixed. A notional interest in the CX16e would be the interest with the greatest standing that fits the argument, so for the sake of argument I was prepared to grant it (pending contradiction).

One thing about the CX16 project is what appears to be a real prospect of a healthy ecosystem of ongoing hobbyist development for the system. One part of that could well be that it appeals to a variety of different niches.

And a system that was perfectly suited to target exactly one of those niches might have some "checklist features" that they like better, but if nobody ever writes any interesting programs for that system, the checklist features don't matter.

So if a bit of compromise against my personal "ideal 8bit retro system" is necessary in order to attract interest from that range of interests, I reckon it's probably a worthwhile trade-off.

The thing that FIRST attracted me to the project doesn't even seem to be a thing anymore, which is that it was going to use the 65816. However, OTOH, given the expansion slot design, putting in a 65816 card that takes over the system bus looks like it would be pretty straightforward, so even if the surface mount 65c02 for the CX16c is soldered in for cost reduction, as long as it has at least one expansion slot, "swapping in" a 65816 looks like it might still be workable.

Indeed, since the 65816 sends the status of the Emulate bit onto a pin (Pin E, 35 in the 40 PIN DIP, Pin 39 in the PLCC, which are NC's in the 65c02), the same CPLD that is handling the takeover of the system bus protocol could trap writes to $0001 and raise the top bit if the 65816 is operating in Native mode, allowing for mirrored Native Mode versions of the system ROM banks ... if, that is, the system ROM banks do not occupy more than half of the System ROM.

 

[StephenHorn]

I suppose I should add, as well, that it is not my intent to be antagonistic. I just find Paul to be frustrating because I don't know what appeals to them about the X16, and I feel that they spend a significant amount of effort arguing that the X16 isn't meeting any particular goals.

[rje]

3 hours ago, BruceMcF said:

One thing about the CX16 project is what appears to be a real prospect of a healthy ecosystem of ongoing hobbyist development for the system. One part of that could well be that it appeals to a variety of different niches.



And a system that was perfectly suited to target exactly one of those niches might have some "checklist features" that they like better, but if nobody ever writes any interesting programs for that system, the checklist features don't matter.



So if a bit of compromise against my personal "ideal 8bit retro system" is necessary in order to attract interest from that range of interests, I reckon it's probably a worthwhile trade-off.

I have to go back to 8BitGuy's vision:

* An alternate-universe VIC-20 with 1989 levels of performance.  A gap the Commodore 65 might have filled.

 

I think his goal is:

* An ecosystem for retro interest, nerd hobbyists, and the demoscene.

 

I think Ultima VI may be his benchmark.

Voila' the CX16.

 

[ZeroByte]

3 hours ago, BruceMcF said:

One thing about the CX16 project is what appears to be a real prospect of a healthy ecosystem of ongoing hobbyist development for the system.

To me, that's the #1 reason to embrace the system in whatever form. If you don't wanna shell out bux for a real computer, you can still run it in emulation and, there's both an audience for any nifty programs you may write, along with a source of nifty programs to try out.

I'm hoping this situation continues until we start to see games come out that actually push the system so we can see what it really can do. I think something north of Genesis and south of SNES, but not right on the line between them, as it could provide "Lucasfilm/Sierra" style adventure gaming that would easily supass both of those systems.

The X16 pushed to its limits will result in a very interesting type of gaming experience IMO.

[paulscottrobson]

15 hours ago, BruceMcF said:

One thing about the CX16 project is what appears to be a real prospect of a healthy ecosystem of ongoing hobbyist development for the system. One part of that could well be that it appeals to a variety of different niches.



The thing that FIRST attracted me to the project doesn't even seem to be a thing anymore, which is that it was going to use the 65816. However, OTOH, given the expansion slot design, putting in a 65816 card that takes over the system bus looks like it would be pretty straightforward, so even if the surface mount 65c02 for the CX16c is soldered in for cost reduction, as long as it has at least one expansion slot, "swapping in" a 65816 looks like it might still be workable.



 

You (sort of) asked what my motivation was. This pretty much sums it up. What is lacking in all the other retrosystems, with the possible exception of the Mega65 and Spectrum Next is any kind of software ecosystem.

The problem is you can't have both of these at the same time. The BBC is a good example of this. There was little or no software for the Tube add ons ; the ARM one was I think used to develop the Archimedes, the fast 6502 one was used to produce a solid 3D elite. There was a Z80 CP/M board called Torch which had access to the CPM library. But there's no real software for it.

In practice software development is for the basic system, unless there is a simple and common upgrade (say Spectrum 16k -> 48k). Some limited upgrades can be supported (say the AY chip in later Spectrum, or the use of the extended memory to avoid repeated tape uploading). But most of the 'updates' in software tend to be incidental. So the Freescape thing runs better on the Next simply because the processor can do more in the time available, and it's synced by the VSYNC interrupt.

My concern, fundamentally, is that the limitations of the CPU handicaps development. It could have been worked round in one of two ways. Having a very fast 6502 like the Mega65 does. That allows you to use VMs much more effectively, or in the case of your FORTHs loses the hit of the execution loop and only having one real stack. Or to plug a 65816 in it, which gives you lots of memory and native 16 bit data if you want it and the option of putting VERA memory in CPU address space.

Plugging in a 65816 expansion board or anything else just means that there's a seperate tiny software ecosystem limited to the few that have that board.

[paulscottrobson]

11 hours ago, ZeroByte said:

To me, that's the #1 reason to embrace the system in whatever form. If you don't wanna shell out bux for a real computer, you can still run it in emulation and, there's both an audience for any nifty programs you may write, along with a source of nifty programs to try out.



I'm hoping this situation continues until we start to see games come out that actually push the system so we can see what it really can do. I think something north of Genesis and south of SNES, but not right on the line between them, as it could provide "Lucasfilm/Sierra" style adventure gaming that would easily supass both of those systems.



The X16 pushed to its limits will result in a very interesting type of gaming experience IMO.

It's very good at tiles and sprites or simple PETSCII displays, but not very good at direct screen memory access stuff. Michael Steil and I have both written line routines for it, entirely seperately, and they run at about the same speed, a couple of lines a frame in 320x256 mode. I'm sure my code could be made to run quicker but not that much quicker. You could reduce it to 256x256 and do everything in 8 bit data I suppose, but that's no use for OS routines.

So I reckon apart from tile maps (possibly scrolling) with sprites type games (or just sprites, it should do Robotron well say !) it's not going to be an improvement on its predecessors.

As for static graphics adventures, you've got 320x256 mode with 256 colours, or double a resolution with 16 colours. It's going to be about the same as EGA with the VGA 320x2xx x 256 colour mode. VERA has slightly less memory than a standard EGA card (I think originally there was a 64k version).