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(new title): Hard decision, but the answer is pretty clear.


x16tial
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1 hour ago, Lasagna said:

No the ZX-Uno is usually around 70 Euros with VAT and would be much cheaper if produced in larger quantities.

X8 is already a two chip device with an ESP32 for wireless..

Well, that's useful. I just clicked on the first two links I got, but since Google is blocked in Beijing, that was on Bing, and it can be iffy as a search engine. As you attempt to persuade the CX16 project to abandon it's project and become a ZX-Uno project instead, that kind of info would be handy.

And it's good news ... that makes it more likely that the CX16e would be on the $70 side of the range than the $100, which is encouraging ... because it implies it is more likely that the X8 would end up on the $35 dollar side of the range than the $50.

Regarding David not knowing what he is talking about when he says the X8 would cost half as much as the X16e? You're not going to convince me on that front.

Regarding the ESP32, are you sure that's intended for the finished board and is not just there for development purposes? I got excited when I saw that, but a cooler head figured it was probably just for system development and wasn't intended as part of the finished product.

Edited by BruceMcF
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17 hours ago, Lasagna said:

To me the X8 feels like a design constrained by the skills of the FPGA designer - someone knows the X16 FPGA (I forget is it Xilinx? Lattice?) and that specific FPGA toolchain really well and is shoehorning the design into that FPGA when we could have all the things we want, memory, real ports, and expansion, going with a ZX-UNO forked solution.

Consider the possibility that you know much less than the FPGA designer...

Of course it feels like the X8 design is shoehorned into the FPGA.  It was.  I don't know the primary motivation.  It could be cost, desire to reuse hardware or simply the fun challenge of seeing how much function could be crammed into a cheap FPGA.

17 hours ago, Lasagna said:

And the cost would likely end up about the same.

Unlikely.  The ZX-UNO RAM by itself costs about the same as the CX8 FPGA.  Everything else is kinda-sorta similar so the cost delta is dominated by the ZX-UNO FPGA.  That's 20 bucks or so in hobbyist quantities.

It's not surprising that the higher cost external RAM + bigger FPGA design point is higher function than the embedded RAM/smaller FPGA design point.  Spend more, get more.  Both designs have their merits but neither is objectively better.

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1 hour ago, picosecond said:

It's not surprising that the higher cost external RAM + bigger FPGA design point is higher function than the embedded RAM/smaller FPGA design point.  Spend more, get more.  Both designs have their merits but neither is objectively better.

What is interesting is, the $35-$50 price point is chock full of little modern microcontroller SBCs, it is unfilled by that "retro FPGA systems", because the retro FPGA systems that emulate an existing system have a hard lower bound on their capabilities.

Since the X8 is an FPGA simulation of a phantom brother to the CX16 family that doesn't exist, so it doesn't have a hard lower floor on what capabilities it can provide. It is free to just provide the capabilities that fit the FPGA.

But it also justifies the reliance on the 65C02, since what is a transistor-saving design in the 70s and 80s has become a logic resource saving core in the 20s.

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1 hour ago, picosecond said:

Consider the possibility that you know much less than the FPGA designer...

Oh, I'm confident I know much less than the FPGA designer. That's why my primary focus is resting on one of the older tricks in the "pin saving" book, swapping decoded outputs for encoded outputs with an external decoder.

Since I don't think I can out-clever anybody in hardware design, I don't even try, and instead am just focusing on the simplest and cheapest way to make the X8 expandable, leveraging what it is already able to do.

 

Edited by BruceMcF
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1 hour ago, picosecond said:

Of course it feels like the X8 design is shoehorned into the FPGA.  It was.  I don't know the primary motivation.  It could be cost, desire to reuse hardware or simply the fun challenge of seeing how much function could be crammed into a cheap FPGA.

Quite ... since this is a volunteer effort, even if the conversation went, "hey, what if I did a proof of concept", the fun challenge of doing it can easily be the main motivation.

I remember in grad school, some thirty years ago now, a friend of mine was helping a classmate fix a nagging problem with their Toyota pick up. I was around the gang office when the classmate dropped by to thank my friend. His answer was, "Hey, no problem, it gave me a good excuse to buy the metric tools I needed."

I didn't say anything, but it struck me at the time how that represent the "Instinct of Workmanship".

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