I've been writing with a 65C816 new emulator for the PIC32MX and I'm thinking of building some tiny PCBs about the size of a match box for it. The spec will be something like:

Emulated 65C816 in PIC32MX270F256B (28 pin SOIC)
60K RAM ($00:0000-$00-efff)
4K Boot ROM ($00:f000-$00:ffff)
3x 64K ROM ($01:0000-$03:ffff)
USB Serial (via a MCP2200)
SPI SD card
SPI RTC (possibly)
GPIO ports

Its hard to tell exactly how fast the emulator will run. At the moment it looks like a I'm taking around 10 MIPs instruction per 65C816 cycle so at 48Mhz (70MIPS) that should be about 7Mhz equivalent. Probably closer to 6Mhz when I've added interrupt generation and virtual peripherals.

If there is interest I might make a number for sale.

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Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

I found a new and faster (72Mhz 113 MIPS) chip in the same family PIC32MX174F256B. I've ordered some to try it out.
I was going to include a small monitor with a download command to allow the flash holding the ROM banks to be updatable without having to reprogram the PIC.

It's going to be powered by USB and have a USB serial adapter on board. I want to have a micro SD card socket on the pcb connected to a hardware SPI port. I'll bring the pins and some spare selects out to a header along with a second serial line and i2c.

The code should be movable to a PIC32MZ later for 200MHz 330MIPs performance with more RAM (~512K) and Flash ROM (maybe 1.5M) but for that one the boot ROM will be copied into RAM in startup to make the memory mapping easier/faster (Bank 0 will be 64K RAM). I bought some dev boards a while back to try this out on.

https://web.archive.org/web/20190417214629/https://www.olimex.com/Products/PIC/Development/PIC32-HMZ144/open-source-hardware

_________________
Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs

Sounds very interesting! Very reasonable performance, a very functional chip, compact, presumably low power, and 5V tolerant I/Os.
https://www.microchip.com/wwwproducts/e ... MX270F256B

And if successive chips get the emulated performance above the magic 14MHz, so much the better! Of course 6MHz or so is already pretty good. (And with an emulated 65816, throwing in a multiply instruction, CRC generator, or similar point acceleration could make a huge difference.)