256 regions = 8 words

	((vma-start-read) (a-constant (+ 400 %sys-com-number-regions)))
	(illop-if-page-fault)
	((m-a) ldb (byte 20. 5) md)		;divide by 32
	((m-b) a-disk-run-light)
	((m-b) sub m-b (a-constant (eval (+ 32. 32. 12. -1))))
	((a-boot-progress-base) m-b)
	((md) setz)
	((m-c) m-a)
	((m-d) m-b)

clear-top-row
	((vma-start-write) m-d)
	(check-page-write-no-interrupt)
	((m-d) add m-d (a-constant 1))
	((m-c) sub m-c (a-constant 1))
	(jump-not-equal m-c a-zero clear-top-row)

	((md) seto)
	((m-d) add m-b (a-constant 32.))
	((m-c) m-a)
draw-bottom-row
	((vma-start-write) m-b)
	(check-page-write-no-interrupt)
	((m-b) add m-b (a-constant 1))
	((m-c) sub m-c (a-constant 1))
	(jump-not-equal m-c a-zero draw-bottom-row)


set-boot-progress-bit-for-this-region
	((m-a) ldb (byte 20. 5) m-ap)		;get word number
	((m-b) ldb (byte 5 0) m-ap)		;get bit in word
	((vma-start-read) add m-a a-boot-progress-base)
	(check-page-read-no-interrupt)