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platform-amstradnc

README.md

Support for the Amstrad NC series of Z80 portable computers.

Supported Platforms

  • Amstrad NC100
  • Amstrad NC150 (use the NC100 image, no serial floppy support)
  • Amstrad NC200
  • Dreamwriter 225

Known Bugs

  • Suspend/Resume is broken on the NC100. On an NMI shutdown you'll not be able to get back

Use:

TARGET=amstradnc/nc100 for the NC100
TARGET=amstradnc/nc200 for the NC200

The NC100 supports hda on the PCMCIA card. The NC200 supports hda on the PCMCIA card and fd0 on the internal floppy drive (720kB standard PC formats). The 720kB image from fuzix.org will just work.

Use 0 to boot from PCMCIA, 256 to boot from floppy.

Building

make diskimage

This will create the following image files in Images/amstradnc/...

  • fuzixboot.img: raw disk image for the boot floppy
  • fuzixboot.DSK: emulator disk image for the boot floppy
  • fuzixroot.img: floppy root image
  • fuzixroot.DSK: emulator floppy root image
  • pcmcia.img: raw image (can be used with emulator) of the PCMCIA card

The floppy images are only created on the NC200 series machines. The PCMCIA image differs between the NC100 and NC200.

Installation to floppy

NC200 only.

Build the kernel and then dd fuzixfloppy.img to a raw 720kB floppy. dd a root file system to a different floppy. Start the NC200, insert the kernel disk, and then press YELLOW+R. The boot looader will start, load the kernel, and you'll be left at the Fuzix bootdev prompt. Change floppies and use 256 to mount the floppy root.

Bonus tip: if you format your disks on the NC200 itself, it'll boot faster (due to using non-standard sector skew).

Installation to PCMCIA card

This currently works on the NC100 only (the NC200 won't boot from PCMCIA yet).

On a PC, do:

$ mkfs filesystem.img 64 1408  
$ ucp filesystem.img  
(copy files into the filesystem here)

then

$ dd if=fuzix,bin of=mycard.img bs=16384  
$ dd if=myfs of=mycard.img bs=16384 seek=20 conv=notrunc

Now copy mycard.img onto the PCMCIA card. Insert into the NC100 and do YELLOW+X to boot. At the bootdev prompt, use 0 to mount the PCMCIA file system.

Note: The Linux PCMCIA support in modern systems is generally terminally broken and orphaned. The best approach is to load a very old Linux (2.4 era) onto an old laptop and use that. It's also cheaper to buy an old laptop than the various insanely priced modern adapters for PCMCIA memory cards.

Booting with nc100 and nc200

The NC200 emulator from the RC2014 emulator git can run the NC200 version of the system but as it currently lacks a disk change command you'll need to use the PCMCIA root file system. Unlike the NC100 you will need a set of genuine ROM images from your actual NC200.

nc100 -r nc100.rom -p pcmcia.img

nc200 -r nc200.rom -p pcmcia.img -A fuzixboot.DSK

NC100 memory map

16K arbitrary banks.

No CP/M emulation (due to NMI)

0x0000	Vectors  
0x0100  Application  
0xEFFF  Application end  
0xF000  Common, uarea  
0xFFFF	Common top  (including video helpers)

Overlaid with

0x0000	Vectors  
0x0100  Bootstrap code  
0x0213	Kernel  
0xBFFF  End of kernel space

Overlaid at times with
0x4000-0x7FFF video bank (vram used by ROM OS)

NC200 is similar but CP/M should be possible

On the PCMCIA card the layout looks like

0,1,2		Bootblocks, state, kernel  
3,4,5		Running kernel  
6		Initial common (boot and inherited by init)  
8-19		User pages (12 * 16K)  
20-63		Filesystem

NC200 differences

The NC200 differs from the NC100 in various ways we care about

  • Video default is at 0xE000 (DONE)

  • Display height is doubled (DONE)

  • Display is designed for 80 column x 16 lines in 6x8 characters (we need a 6x8 font and driver for this)

  • 0x70 bit 2 = 0 for backlight on ?

  • The keyboard is bit 3 as before but bit 4 is now power switch rather than it causing an NMI (so we can do CP/M emulation)

  • serial interrupts are bit 2 on NC200 and bit 0 on NC100

  • NC200 requires keyboard interrupts are explicitly cleared, NC100 doesn't in fact care (but its harmless to do so) (DONE)

  • Need to mask the serial interrupt when the line driver is off (may need that on NC100 too ideally) (DONE)

  • The keymap is slightly different (see ZCN) (DONE)

  • Parallel port busy is now on 0x80 bit 0 ? (DONE)

  • Different rtc (same base address but a 146818 not a tc8521)

  • There is a floppy drive, this is sort of described in MESS

    0x30 bit 5 set to 0 for FDC use ?
    0x60 bit 5 is the FDC interrupt (same bit masks in 0x90 as usual)
    0x70 bit 1 is the disk motor (1 = off)
    0x70 bit 0 is the 765 terminal count
    0xE0/E1 is the upd765

Todo

  • driver for the power status bits
  • lots of testing
  • control doesn't seem to work ???
  • pick codes for the arrow keys
  • NMI/resume
  • this platform would really benefit from vfork
  • floppy control/formatting
  • serial format bits
  • rts/cts
  • dynamic buffer cache
  • suspend/resume
  • clean up and debug nc100 startup a bit
  • full rtc support
  • bigger font on nc200