Yep, I would not start with an mcu with 64kB ram and 128kB flash today.
I don't want another Linux SBC.
I don't want another Linux SBC.So dont install linux on it? Bare metal the JH7110 and treat it just like a traditional short pipeline CPU. How do you expect USB to work with a low MHz CPU ?
I had built my first SBC in 1982 (8085 based) and since then I learned following - in the moment I get a great idea I let the idea "settle". By distracting myself in doing something else.. After a month or two or three I evaluate the idea again, and usually my interest in that idea gets lost (for hundreds of reasons). Try it, it works
99.9% of people who potentially would consider your design want to "run" something on it - an OS, apps, games, utilities, etc. Or do you target those 0.1%
IMHO you should decouple your desire to gain hands-on RISC-V experience from your desire to build a retrocomputing (or retro-styled) platform.
I don't want another Linux SBC.So dont install linux on it? Bare metal the JH7110 and treat it just like a traditional short pipeline CPU. How do you expect USB to work with a low MHz CPU ?I've already said it: "I am tired of Raspberry Pis with amazing quad-core CPUs running light switches...", as for USB that part is built into MCU. I've posted picture of the evaluation board above.
Note on video resolutions:
It is crucial to me that this computer has specific constraints regarding its video capabilities. I'm not interested in high resolutions; I prefer the primary resolutions to be approximately 320x240 pixels and 640x480 pixels. I wish to maintain these settings to facilitate pixel art creation on this machine. Additionally, it's essential for the machine to produce a 15kHz signal suitable for display on standard CRT TVs, catering to all CRT RGB enthusiasts. Technically, the computer would be capable of SVGA (800x600) or perhaps higher resolutions as well. But, that's just a bonus.
IMHO most owners of retro computers prefer to connect them to a modern TV and pay for composite-to-HDMI converters. I really don't see a point of composite or VGA interface. Among many retro computer related channels on youtube, how many of them use CRT monitors?
As a thought, to get maximum flexibility while keeping costs low, you could add a low-cost FPGA in your design, to implement specific controllers, display stuff, etc. For this, I think a low-cost FPGA would work out, for instance something in the Lattice ICE40 series - that would merely add a few bucks to the BOM. You'd still keep the MCU to run software and communicate with the FPGA. Certainly that would keeps costs low as opposed to using a single FPGA for both implementing custom controllers and the MCU core, which would require a much beefier, and thus much more expensive FPGA. (To get some perspective, getting anywhere close to the performance of a CH32Vxx at 144Mhz with a soft core on FPGA would require a relatively expensive FPGA.)
(...) thinking you can handle n-number of USB ports with n user selected peripherals on a 100MHz microcontroller.... without using linux, is incompatible with the level of experience you have expressed in your posts.
Right sizing is important when you are going volume production and saving a few dollars makes $$$$ return. Pointless here. Doesn't matter if the chip has more than you need when it has what you need and is ready to go. Trying to do some custom board and platform is a huge investment (which you have not stated your idea of budget).
A community is not going to form around some new arbitrarily intentionally limited platform, there are plenty of competitive platforms already established and you seem be bringing "RISC-V WOOOOO" and thats about it, except others got there first.
As a thought, to get maximum flexibility while keeping costs low, you could add a low-cost FPGA in your design, to implement specific controllers, display stuff, etc. For this, I think a low-cost FPGA would work out, for instance something in the Lattice ICE40 series (...)
IF you want I can help you realize the electronics part of the project. Meaning designing a PCB and electrically testing it, making sure the PCB works. I've offered similar consulting before, and I have lots of experience designing PCBs. Send me a direct message if you are interested, we discuss the details.