Loadable POST - 
   Load from fixed disk or diags diskette. They run after Resident POST. The loadable POST programs first sense the adapters and options installed in the system unit  and build an Installed Features List. Before any checkout routines are run, the installed  features list is compared to the Configuration Record on the fixed disk. See page 2-6 for  more info.

    NOTE: Pressing Ctrl - Alt - Pause causes the Loadable POST programs to run.
   When u is shown in the chart, it is displayed in the upper half of the two-digit display.
   RT FAQ and IBM RT PC 6151 System Unit Hardware Maintenance and Service, pgs 2-6 thru 2-8.

Loadable Power On Self Test routines (LPOST)
       The initial IPL sequence of LED codes are listed in the hardware FAQ. After LED code 22 and 26 is displayed control is passed to the loadable VRM boot code.  As VRM is booting, these LED codes are displayed by Loadable Power On Self Test routines (LPOST).

LPOST LED values during IPL
30      Monochrome display adpater
31      Color graphics adapter (EGA).
32      6153 display adapter.
33      6154 display adapter.
34      6155 display adapter.
35      Fixed disk in location C.
36      Advanced processor card.
39      Diskette in location A.
40      Diskette in location B.
43      PC AT Coprocessor option.
44      Floating-Point accelerator.
45      Monochrome display/Printer adapter.
46      3278/79 emulation adapter.
47      Memory card in slot C bad - 4Meg enhanced card.
48      Memory card in slot D bad - 4Meg enhanced card.
49      RS-232C 8-port adapter.
50      PC Network adapter.
51      Serial device - serial/parallel adapter.
52      SCSI adapter.
53      RS-232C 4-port adapter 1
54      Parallel device - serial/parallel adapter.
55      RS-232C 4-port adapter 2.
56      RS-422A 4-port adapter 1.
57      RS-422A 4-port adapter 2.
58      5080 attachment adapter.
59      S/370 attachment adapter.
5U      Memory expansion option or Enhanced Advanced processor and  Memory Mgmt. card.
60      Multiprotocol communications adapter.
61      5080 peripheral adapter.
62      Baseband adapter.
63      Lighted PF keys.
64      Dials.
65      5081 display adapter 1.
66      5081 display adapter 2.
67      Advanced floating-point accelerator.
68      Floating-poing processor on Advanced Processor and Memory Mgmt. card.
69      Memory option on Advanced processor and Memory Mgmt. card.
71      Memory card in slot C bad - 2 Mb card.
72      Memory card in slot C bad - 1 Mb card.
73      Memory card in slot C bad - 4 Mb card.
74      Memory card in slot C bad - 8 Mb enhanced card.
76      Memory card in slot D bad - 1 Mb card.
77      Memory card in slot D bad - 2 Mb card.
78      Memory card in slot D bad - 4 Mb card.
79      Memory card in slot D bad - 8 Mb enhanced card.
80      Mouse device.
81      keyboard device.
82      Speaker device.
84      Bus memory cards.
85      Tablet device.
86      Token ring network adapter.
87      RS-422A 8-port adapter.
88      Reserved (Power on).
90      Streaming tape adapter.
93      Diskette read/write error.
94      Final LPOST found no display - Fatal.
95      Fixed-disk write error.
9c      MIL-STD 188 8-port adapter.
cc      6156 portable disk drive model 3.
cu      6156 portable disk drive model 1.
uc      6192 expander card.
uu      6192 receiver card.