Quote:
Originally Posted by alexh
Would MiniMig have anything close to a floppy emulator? Because you have both ends of the system wouldn't he have simplified the inner workings of the Amiga FDC and how it is coupled to the SD card? I don't think the RTL which makes up MiniMig could be wired up to a floppy disk drive and function with minor tweaks, I imagine it would be a re-write. But I could be wrong.
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Yes Minimig has a floppy emulator implemented on an external PIC CPU, it looks like you stick SD cards in one side with WinUAE images on and MFM comes out the other. Straightforward - especially compared to the FPGA stuff.
The only tweak comes with the amount of RAM you have available on chip and the timer precision. Most small microcontrollers (lower than ARM SoCs) usually don't have PLL clock multipliers and are designed to use teeny power and be cheap rather than wind up fast. Also 8 bit MCUs are just tediously inefficient in many ways compared to arm; writing some assembler for my Atmega board here reminds me of the Amstrad days. Do you remember how tedious it is to add one to a 32 bit number with only 8-bit registers? ;-)
ARMs rule in general, but ARM SoCs perform particularly well b/c they wind up to mad clock speeds via the aftorementioned PLL, have proper 32-bit registers, and usually have 32-bit single-cycle SRAM all on chip. They have a chaming ability to overclock (purely in software- yay) because nothing fast ever leaves the chip itself. In our case (no peripherals except USB) I'm hopeful we can run it at 96Mhz and it probably won't even get perceptably warm to the touch.
Mainly though, they're cheap and extremely easy to wire up. You could probably even do this whole shebang on a single-sided PCB with one chip, two connectors (usb+floppy), a couple of decoupling caps and a crystal if you were sneaky with the routing.
Oh yes one final thought re floppy emulator; errrrm yes I think we can make cyclone20 work seamlessly as both drive controller and emulated drive. Potentially I think everything can be done in software (just changing direction of a few of the lines) although actually you'd probably want to swap the read and write lines (two wires) over when pretending to be a drive as those two IO ports have Special Powers.