[website_subgeniuskitty.com] / data / development / pdp-11 / references / kdj11_tips.md

# Overview #

A collection of tips for working with KDJ11 CPU boards.

# Failed Tests #

The KDJ11-B includes a variety of diagnostics in ROM that run on boot. When a
test fails, there is a hidden option to bypass the test and continue. Simply
press `Ctrl-O` (the letter, not the number zero), then `4`, then `ENTER`. This
will continue on, halting at the next failed test or at the boot menu.

# J11 ODT & Cache #

When a KDJ11 with cache powers up, the cache is enabled by default, even in
ODT mode. Thus, even if a memory location is faulty, writing and reading to
that location will appear to succeed.

The cache may be bypassed by setting bit nine of the Cache Control Register
(CCR) located at `017777746`. In ODT:

    17777746/ 01000
Commit	Line	Data
9c776c90 AT	1	# Overview #
	2
	3	A collection of tips for working with KDJ11 CPU boards.
	4
	5	# Failed Tests #
	6
	7	The KDJ11-B includes a variety of diagnostics in ROM that run on boot. When a
	8	test fails, there is a hidden option to bypass the test and continue. Simply
	9	press `Ctrl-O` (the letter, not the number zero), then `4`, then `ENTER`. This
	10	will continue on, halting at the next failed test or at the boot menu.
	11
	12	# J11 ODT & Cache #
	13
	14	When a KDJ11 with cache powers up, the cache is enabled by default, even in
	15	ODT mode. Thus, even if a memory location is faulty, writing and reading to
	16	that location will appear to succeed.
	17
	18	The cache may be bypassed by setting bit nine of the Cache Control Register
	19	(CCR) located at `017777746`. In ODT:
	20
	21	17777746/ 01000
	22