Commander X16 is on its way...

In case you haven't heard, there's a new 8-bit retro computer being built, and it's new but old.

Try it out online here: https://www.commanderx16.com/forum/index.php?/home/



It's not a clone, so it's a new architecture.  And yet, it re-purposes an old, established architecture, so it's old.

The Commander X16 is a Commodore clone.  Since it uses the Commodore KERNAL and BASIC and runs with a 65C02 processor, it is as compatible with the Commodore family as the other Commodore machines are with each other.  But since it's not a C64 or PET or Plus/4, binaries from them will generally not run on it... unless, that is, the code is in a safe location and uses the KERNAL's jump table.

It supports the IEC serial bus, so you could attach a disk drive if you really wanted to.  But it replaces the cassette port with an SD card slot (good call!).

It's got a neat memory map, too.

The basic architecture draws from the VIC-20, which is uncomplicated: the ROMs are in the highest chunk of memory, and there's static RAM below it.  Static RAM itself is uncomplicated, compared to the dynamic RAM of the C64 and on.  Because we live in 2020, 64K of static RAM is cheap.  Back in the 80s, I suppose it was very expensive.

After that, things get interesting but still not complicated:

There's 39K of RAM, from $0000 to $9EFF.  I'm not sure how that's divided up: I bet it cheaper just to install a single 64K static RAM chip than to install a 32K and a 16K one!

Then there's a page of I/O registers, from $9F00 to $9FFF.

Then, there's 8K of high RAM, from $A000 to $BFFF.  Here's the tricky part though: this 8K window is banked.  In the production model, the bank will be switched at Zero page location $0000 (sound familiar?).  The X16 can have up to 256 banks of this RAM, so up to 2mb of RAM.

After that comes 16K of ROM, from $C000 to $FFFF.  This is where the KERNAL and BASIC ROMs live.  But there's another tricky bit: this 16K window is ALSO banked.  There are already four or five banks allocated, with one for GEOS, one for a proper assembler, another for a Structured BASIC, and so on.

Because 8-bit video chips are nonexistent, there is an FPGA for that.  Sound is still being discussed, I think, but of course the designers want sound to be stereo and at least SID quality.