The CP-Codes Page

The CP-Codes Page
Second Draft, 05. September 1999

This page contains the most common CP codes for the Premium Line PS/2 MCA-machines.

CP stands for Check Points and these CP codes represent a function the system is just proceeding during startup.

The POST Stage 1 is the Power On Self Test carried out after a Cold Start (Power On); the Post Stage 2 is carried out after the stage 1 POST and after a warm boot (with [CTRL]+[ALT]+[DEL]).

The IBM PS/2 Mod. 95 shows the CP-codes on its LED-panel in the system unit front - all other models show the CP-Codes in the bottom line of the screen. However: some are not shown logically, during the time the screen is blanked and the video subsystem is disabled.

On PS/2 Models the CP-codes are also sent to the LPT-port !

If you can handle a solder iron you could create a little adapter to enable you reading the CP codes - either with a separate hardware logic or another PS/2 machine.
For details see here !

CP : xx state/meaning, shown during Machine initialization (POST phase 1 and 2) CP output during Stage 1 POST
CP	Description
01	Disable clock interrupts, turn off screen, mask off parity, initialize interrupt controller, initialize error logging formats
02	Memory DMA refresh test
03	Channel reset
04	Test planar ports (94, 96, 100, 102) initialize default planar POS
05	Check CMOS/NVRAM for validity, initialize EXPRESSWAY (on Model 90 systems only)
06	Initialize dot clock
07	Enable base memory
08	Base memory testing - data integrity
09	Base memory testing - addressability
0F	Fatal base memory error - recovery not successful

10	Start up drive 80
11	Enable extended memory, initialize base memory, disable SRAM, reset parity/channel check. Initialize row, column of cursor.
12	Test protected mode
14	Initialize the 8259 interrupt controller
15	Initialize the interrupt vectors
16	Initialize BIOS interrupt vectors
17	Verify DMA transfers
18	POS setup, set CMOS clock
1A	Set divide-by-0 interrupt vector

24	Set CMOS equipment byte
25	Check for manufacturing boot request

30	Test DMA transfers
34	Protected mode Shutdown
35	Test video card type error

40	Check for video feature ROM and video presence
41	Reset parity and channel checks, load NMI vector with dummy interrupt handler, test timer, load NMI vector to POST NMI handler
42	Test interrupt mask register
43	Test interrupt mask register with device interrupt
44	Check hot interrupts
45	Check hot interrupts without I/O-memory parity enabled
46	Interrupt mask error
47	Timer 2 read/write, verify Timer 0 bits
48	Verify Timer 2 output
49	Verify Timer 0 on off bits
4A	Verify Timer 2 output
4B	Verify Timer 0 interrupt
4C	Verify Timer 0 count/refresh
4D	Verify Timer 3 NMI
4E	Check keyboard controller for last command accepted

5C	Set hardware interrupt vectors 0-7
5D	Set hardware interrupt vectors 8-15
5E	Set rest of interrupt vectors
5F	Test serial port

62	Turn on drive 0 motor Note 1)
64	Test ASYNC registers, modem control lines, and data loop. If ASCII console selected - initialize ASCII console as system display device
65	Enable timer interrupts
66	Check for manufacturing boot and unmask NMI interrupts Note 2)
6E	Check for system security or CE override conditions, run diskette testing and setup, go load first IML image

80	Start of IML process. SCSI POST
81	Diskette IML. Load and verify IML boot record from diskette
82	Disk IML. Load and verify IML boot record from disk
83	Diskette IML. Diskette recovery from SCSI IML failure. Load in and verify IML boot record from diskette

90 - B6	Protected mode exception

BE	Build descriptor tables for protected mode Note 3)
BF	Completion of descriptor tables for protected mode

C0	Base memory addressing test, extended memory enable, base memory initialization
CA	Cache testing (tag RAM, linefill, DMA snooping)
CB	Second Group Cache Testing - L1 DMA snoop
CC	Second Group Cache Testing - L1 linefill
CD	Second Group Cache Testing - non cacheable range boundary
CE	Second Group Cache Testing - L2 DMA snoop
CF	Second Group Cache Testing - L2 linefill

EB	Dual Bus Interface Controller internal register error

F0	Protected mode initialization
F1	Test interrupts in protected mode
F2	Test exception interrupt in protected mode
F3	Verify 286 descriptor instructions in protected mode
F4	Verify 286 BOUND instruction in protected mode
F5	Verify PUSHALL/POPALL instructions in protected mode
F6	Verify ACCESSRIGHTS function in protected mode
F7	Verify ADJUSTRPL fields in protected mode
F8	Verify LOAD instructions in protected mode
F9	Verify LOAD instructions in protected mode (continued)
FA	Test low meg chip select in protected mode

CP output during Stage 2 POST
CP	Description
01	Flush cache, enable first meg of memory as cacheable, disable clock interrupts, mask off parity
04	End Codes - OS loaded (static afterwards)
0B	Write output port command
0C	Test Keyboard
0D	Write byte command to keyboard controller
0E	Keyboard error

14	Initialize the 8259 interrupt controller
15	Initialize display row count
1B	Count memory size
1C	Protect mode entered, determine extended memory size

20	Extended memory size determined, store in CMOS/NVRAM
21	Extended memory size stored, enter real mode
22	Return from count memory size
23	Set real mode stack and data area
24	Set CMOS equipment byte

34	Protected mode shutdown
35	Test video card type error

40	Initialize the video subsystem, set ASCII vectors, clear manufacturing error flags
41	Reset the data segment
4F	Determine warm start

50	Call extended memory testing
51	Protect mode entered, retrieve extended memory size
52	Address test extended memory
53	Memory test extended memory
54	Extended memory testing complete
55	Check if password is enabled
56	Keyboard and mouse testing
57	Keyboard auxiliary device test
58	Verify an interrupt is generated by the keyboard
59	Keyboard stuck key error
5A	Auxiliary device testing
5B	Reset timer, initialize keyboard
5F	Enable Keyboard interrupts

60	Enable diskette interrupt vector
61	Diskette and FDC test
62	Diskette and FDC test, diskette setup
63	Initialize the BIOS Data Area
65	Enable timer interrupts, check CMOS and battery, check for memory configuration errors
66	Initialize diskette setup
67	Enable interrupts
68	Initialize real mode data segment
69	Perform ROM scan
6A	Initialize printer parameters
6B	Set CMOS RS232, calculate usable memory values for CMOS
6C	Initialize Math Coprocessor
6D	Close window, setup keyboard, initprogs, set cache boundaries, enable cache, check full NVRAM errorlog, set time of day, clear descriptor tables, set POST stack, enable level 71-INT, return to overlay
6E	Cleanup tasks before leaving POST, run boot routine
6F	Boot strap loader, Interrupt 19h

70	Read primary disk/diskette boot record
71	Reset disk/diskette
72	Interrupt 18h path
73	RPL via Interrupt 18h
74	Load Operating System (not verified)

84 - 85	Image overlay
86	Store system partition pointer and system partition type. Return from boot record

90 - B6	Protected mode exception

BE	Build descriptor tables for protected mode
BF	Completion of descriptor tables for protected mode

D0	BASIC and VPD copies from ROM to RAM

F0	Protected mode initialization
F1	Test interrupts in protected mode
F2	Test exception interrupt in protected mode
F3	Verify 286 descriptor instructions in protected mode
F4	Verify 286 BOUND instruction in protected mode
F5	Verify PUSHALL/POPALL instructions in protected mode
F6	Verify ACCESSRIGHTS function in protected mode
F7	Verify ADJUSTRPL fields in protected mode
F8	Verify LOAD instructions in protected mode
F9	Verify LOAD instructions in protected mode (continued)
FA	Test low meg chip select in protected mode

Note 1)
This is the point where the SCSI-drives are started, when they are jumpered without the "Power On Startup" option jumper and use the "Start Device" command from the SCSI-Adapter instead.
Return to CP-code

Note 2)
At that point the cursor *should* jump to the top / right position on the screen on all IML-machines. However it does not on many older Mod. 90 and 95 and some Mod. 9556 / 9557. If you are fast enough you can start the reference from the IML-partition at that point with the keys [CTRL]+[ALT]+[INS]. The interval for this is pretty short though - only a few seconds.
Return to CP-code

Note 3)
After changes to the system memory the machine may hang around at that CP for a while - especially on memory expansions, but also after general changes to the system configuration.
Return to CP-code

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