8 hours ago, Lasagna said:
Lurker here! Hello all.
The X8 is great, but if you look at the open source ZX-UNO (which has been forked with a VGA version), you get everything the X8 has plus you get real game ports, 512K of SRAM, PS/2 port, and an expansion port!
In other words, you get the X16e, except with a different processor family, a different video system, and a different audio system. The various prices of ZX Uno board builds I see in a quick google are €100-€150, which subtracting VAT and doing the exchange is about $100-$150.
8 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.
And the cost would likely end up about the same.
Sure, it might "feel" like that to you, but going with thinking it through instead, the idea that it was designed the way it was because the designer was not sufficiently skilled to design a CX16e is not really that likely.
At present, the X16e CANNOT be designed, because the board that it emulates is only in the prototype stage.
So it seems reasonably clear that the X8 was a proof of concept, showing how much of the X16 as it existed could be fit completely into the FPGA that they were using.
Compared your "he tried to do the X16e but he's not skilled enough to succeed" theory, the proof of concept theory is actually plausible. When they came up with the "three phase" approach, they would want to know how much it would cost. Seeing how far the Vega FPGA alone could go would be a valuable piece of information to judge which larger FPGA in the family would be needed.
It also would give them a data point on whether to freeze the Vera feature set, since giving in to clamoring to make it more of a 16/32 bit era video chip would impact the size of the FPGA as well.
As far as the cost ending up the same, no, almost certainly not. If you move from a ZX-Uno or CX16e type system to the X8, the price is going to fall substantially. The 16Xe might be a touch cheaper, since the ZX Uno has a Z80 core, which is a lot bigger than a 65c02 core. But the estimate of the X8 being half the cost of an X16e ... therefore under half the cost of a ZX Uno ... seems reasonable.
Indeed, the ZX-Uno could be seen as one more argument for dropping the ZX-Uno / CX16e type "two chip" device and doing a "one chip" device instead. While not compatible with the CX family, the equivalent of a CX16e has already "been done". The X8 is far more like being breaking fresh ground.
