diff --git a/chapter2.adoc b/chapter2.adoc
index c9b7ee8..0a16368 100644
--- a/chapter2.adoc
+++ b/chapter2.adoc
@@ -75,7 +75,8 @@ Let's consider a non-priority entry matching all bytes of a transaction. It is l
 Finally, if no such above entry exists, the transaction is illegal with error code = "not hit any rule" (0x05).
 
 
-.IOPMP Block Diagram.
+[caption="Figure {counter:image}: ", reftext="Figure {image}"]
+[title="an example block diagram of an IOPMP. It illustrates the checking flow of an IOPMP. This IOPMP takes three inputs: RRID, the transaction type (read/write), and the request address. It first looks up the SRCMD table according to the RRID carried by the incoming transaction to retrieve associated MD indexes and the corresponding permissions related to these MDs. By the MD indexes, the IOPMP looks up the MDCFG table to get the belonging entry indexes. The final step checks the access right according to the above entry indexes and corresponding permissions. An interrupt, an error response, and/or a record is generated once the transaction fails the permission check in the step.", id=iopmp-block-diagram]
 image::iopmp_unit_block_diagram.png[]
 
 [#SECTION_2_7]
diff --git a/chapter3.adoc b/chapter3.adoc
index e5bbb31..e4a624a 100644
--- a/chapter3.adoc
+++ b/chapter3.adoc
@@ -59,6 +59,18 @@ This format is based on Format 1, except *HWCFG0.md_entry_num* is programmable.
 === IOPMP Models
 For the sake of convenience of discussion, some highly used combinations of *HWCFG0* have an alias name, which are *srcmd_fmt*=0 and *mdcfg_fmt*=0 as the full model, *srcmd_fmt*=0 and *mdcfg_fmt*=1 as the rapid-_k_ model, where _k_ = (*md_entry_num* + 1), *srcmd_fmt*=0 and *mdcfg_fmt*=2 as the dynamic-_k_ model, where _k_ = (*md_entry_num* + 1), *srcmd_fmt*=1 and *mdcfg_fmt*=0 as the isolation model, and *srcmd_fmt*=1 and *mdcfg_fmt*=1 as the compact-_k_ model, where _k_ = (*md_entry_num* + 1).
 
+[caption="Figure {counter:image}: ", reftext="Figure {image}"]
+[title="an example block diagram of the rapid-4 model. The flow is the same as in <<iopmp-block-diagram>>, except the MDCFG table is simplified to a constant mapping illustrated in the dashed box. In this example, every MD has exactly four entries."]
+image::iopmp_unit_block_diagram_rapid_4.png[]
+
+[caption="Figure {counter:image}: ", reftext="Figure {image}"]
+[title="an example block diagram of the compact-4 model."]
+image::iopmp_unit_block_diagram_compact_4.png[]
+
+[caption="Figure {counter:image}: ", reftext="Figure {image}"]
+[title="an example block diagram of the model implements SRCMD table format 2 and MDCFG table format 1 with HWCFG0.md_entry_num is 0. In this example, every MD has exactly single entry, i.e., the entry index is equal to the MD index."]
+image::iopmp_unit_block_diagram_srcmd_fmt2.png[]
+
 [#SECTION_3_5]
 === Configuration Protection
 The term 'lock' refers to a hardware feature that renders one or more fields or registers nonprogrammable until the IOPMP is reset. This feature serves to maintain the integrity of essential configurations in the event of a compromise of secure software. In cases where a lock bit is programmable, it is expected to be reset to '0' and sticky to '1' upon receiving a write of '1'.
diff --git a/images/iopmp_unit_block_diagram.png b/images/iopmp_unit_block_diagram.png
old mode 100644
new mode 100755
index 5bd1810..738ad7b
Binary files a/images/iopmp_unit_block_diagram.png and b/images/iopmp_unit_block_diagram.png differ
diff --git a/images/iopmp_unit_block_diagram_compact_4.png b/images/iopmp_unit_block_diagram_compact_4.png
new file mode 100755
index 0000000..3b78bda
Binary files /dev/null and b/images/iopmp_unit_block_diagram_compact_4.png differ
diff --git a/images/iopmp_unit_block_diagram_rapid_4.png b/images/iopmp_unit_block_diagram_rapid_4.png
new file mode 100755
index 0000000..cc2320a
Binary files /dev/null and b/images/iopmp_unit_block_diagram_rapid_4.png differ
diff --git a/images/iopmp_unit_block_diagram_srcmd_fmt2.png b/images/iopmp_unit_block_diagram_srcmd_fmt2.png
new file mode 100755
index 0000000..d3be0ee
Binary files /dev/null and b/images/iopmp_unit_block_diagram_srcmd_fmt2.png differ
diff --git a/intro.adoc b/intro.adoc
index 9dd72eb..32fd84f 100644
--- a/intro.adoc
+++ b/intro.adoc
@@ -10,5 +10,3 @@ Another hardware component in a bus matrix, the Input-Output Memory Management U
 
 .Examplary Integration of IOPMP(s) in System.
 image::iopmp_system_position.png[]
-
-