CP/M ROMDISK
============

- implemented on port 0x0F:
--- write track number (0..191)
--- read 128 times
--- not writeable
--- 44 tracks reserved for CPM.SYS

- create/populate image with
--- mkfs.cpm -f romdisk -b cpm.sys <image>
--- cpmcp -f romdisk <image> <hostfile> <user>:

DPB:
> SPT = 1
> BSH = 3
> BLM = 7
> EXM = 0
> DSM = 23
> DRM = 32
> AL0 = 128
> AL1 = 0
> CKS = 0
> OFF = 44

/etc/cpmtools/diskdefs:
> diskdef romdisk
>   seclen 128
>   tracks 192
>   sectrk 1
>   blocksize 1024
>   maxdir 32
>   skew 1
>   boottrk 44
> end