I should make the point clear that the PIC16F1825 firmware is
deprecated at this point and anyone building a device should be using the PIC16F1704 and its associated firmware. I would have pointed this out to CayMac Vintage, except I didn't know they were selling TashTwenty devices until someone else mentioned it to me (they're welcome to do so, of course, as is anybody else, the firmware and PCB designs are open source for that reason).
The 1825 firmware still works and both devices are pin-compatible, but in addition to the support for custom icons, the 1704 firmware uses the memory card adapter's activity light to blink out a trouble code whenever there's an issue with the card that keeps it from functioning - it's nice when troubleshooting issues not to have to lead with "do you own an oscilloscope". =) Also, it should be slightly faster - the 1825 firmware loads a sector into memory before transmitting or storing it, while the 1704 copies data directly in both directions (though the biggest limiting factor is the speed of the DCD interface to the Mac).
While I'm looking forward to the Mega board as much as anyone else, it won't allow for any more DCD devices than are currently supported by any other TashTwenty board - the limitation of 2 or 4 DCD devices in a daisy chain is purely in the ROM. DCD itself, in fact, places no limit on the number of DCD devices that can be daisy chained - it only knows "select first device" and "select next device" - a single daisy chain could support an infinite number of DCD devices if not for limits imposed by the ROM (and by cabling, of course).
As
@JDW pointed out, TashTwenty has no way to support MOOF images as it only emulates DCD devices (i.e. HD20-like devices). DCD is a high-level protocol that effectively repurposes the IWM-based floppy interface to act as a high-speed serial interface and it deals directly in digital data in much the same way SCSI does - the Mac only knows it's dealing with a storage device, it doesn't know or care what the underlying media is.
I would like to produce my own full-fledged floppy drive emulator at some point, but it's a difficult task to begin with and some restrictions I've placed on myself make it more so - I could probably have completed it by now if I was using a more advanced embedded system, but I like working with 8-bit PICs and SPLDs because I am silly, and I write firmware for fun, not profit. =) Maybe someday. TashTwenty pleases me as a project because its logic is entirely contained within a single 8-bit PIC, no FPGA or CPLD or SPLD needed... I'd tried to develop a floppy emulator that was entirely self-contained as well, but the necessary tradeoffs would have made it a less functional device than I want to deliver.
Anyway, I'm glad others are producing devices and making them available for sale and I hope that everyone who wants one is able to get one - operating a store is not where my interest lies. It makes me happy that people are discovering TashTwenty and finding it useful. That's all I hope for with all my projects (like
TashTalk,
TashThird, and
TashIO... check 'em out if you haven't already!) =)