Finally understand location 7 (incremented at 60Hz)
setting it to -1 causes clock interrupt every jiffy
Improve comments in dsktrans
Clarify cnop/cskp usage in iread/iwrite code
iwrite and iread have common code
entry at iwrite save return address at iread
and overwrites return address to "skp" inst
entry at iread puts "nop" inst at iwrite
"xct iwrite" skips on write entry
phil