diff --git a/blk/001 b/blk/001
index e60eec1..ea1c2d5 100644
--- a/blk/001
+++ b/blk/001
@@ -6,7 +6,7 @@ MASTER INDEX
 150 Extra words
 200 Z80 assembler             260 Cross compilation
 280 Z80 boot code             350 ACIA driver
-370 SD Card driver            390 Inner core
+370 SD Card driver            390 Cross-compiled core
 420 Core words                480 AT28 Driver
 490 TRS-80 Recipe             520 Fonts
 550 TI-84+ Recipe
diff --git a/blk/390 b/blk/390
index 3873ffc..430b8c9 100644
--- a/blk/390
+++ b/blk/390
@@ -1,16 +1,14 @@
-Inner core
+Cross-compiled core
 
-This unit represents core definitions that happen right after
-native definitions. Before core.fs.
+This units contains core Collapse OS that are cross-compiled.
+During building, these come right after the boot binary (B280).
 
-Unlike core.fs and its followers, this unit isn't self-
-sustained. Like native defs it uses the machinery of a full
-Forth interpreter, notably for flow structures.
-
-Because of that, it has to obey specific rules:
-
-1. It cannot compile a word from higher layers. Using
-   immediates is fine though.
+Because this unit is designed to be cross-compiled, things are
+a little weird. It is compiling in the context of a full
+Forth interpreter with all bells and whistles (and z80
+assembler), but it has to obey strict rules:
 
+1. It cannot compile a word from higher layers. Immediates are
+   fine.
 
                                                         (cont.)
diff --git a/blk/391 b/blk/391
index b423ea6..99af87b 100644
--- a/blk/391
+++ b/blk/391
@@ -1,16 +1,16 @@
-2. If it references a word from this unit or from native
-   definitions, these need to be properly offsetted because
-   their offset at compile time are not the same as their
-   runtime offsets.
-3. Anything they refer to in the boot binary has to be properly
-   stabilized.
-4. Make sure that the words you compile are not overridden by
-   the full interpreter.
-5. When using words as immediates, make sure that they're not
-   defined in icore or, if they are, make sure that they are
-   *not* offsetted
+2. Immediate words that have been cross compiled *cannot* be
+   used. Only immediates from the host system can be used.
+3. If an immediate word compiles words, it can only be words
+   that are part of the stable ABI.
 
+All of this is because when cross compiling, all atom ref-
+erences are offsetted to the target system and are thus
+unusable directly. For the same reason, any reference to a word
+in the host system will obviously be wrong in the target
+system. More details in B260.
 
-
-
-                                                        (cont.)
+This unit is loaded in two "low" and "high" parts. The low part
+is the biggest chunk and has the most definitions. The high
+part is the "sensitive" chunk and contains "LITN", ":" and ";"
+definitions which, once defined, kind of make any more defs
+impossible.                                             (cont.)
diff --git a/blk/392 b/blk/392
index 5afcd1f..cb095cb 100644
--- a/blk/392
+++ b/blk/392
@@ -1,15 +1,3 @@
-Those rules are mostly met by the "xcomp" unit, which is
-expected to have been loaded prior to icore and redefines ":"
-and other defining words. So, in other words, when compiling
-icore, ":" doesn't means what you think it means, go look in
-B260.
-
-This is loaded in two "low" and "high" parts. The low part is
-the biggest chunk and has the most definitions. The high part
-is the "sensitive" chunk and contains "LITN", ":" and ";"
-definitions which, once defined, kind of make any more defs
-impossible.
-
 The gap between these 2 parts is the ideal place to put device
 driver code. Load the low part with "393 LOAD", the high part
 with "415 LOAD"
diff --git a/blk/420 b/blk/420
index 991ea67..fd6f127 100644
--- a/blk/420
+++ b/blk/420
@@ -1,12 +1,12 @@
 Core words
 
-These words follow Inner core words, but unlike them, these are
-self-bootstrapping and don't depend on the Cross Compiler. They
-will typically be included in source form right after a stage1
-binary which will interpret it on boot and bootstrap itself to
-a full intepreter, which can then be relinked with the
-Relinker. There is no loader for these libraries because you
-will typically XPACK (B267) them.
+These words follow cross-compiled words, but unlike them, these
+are self-bootstrapping and don't depend on the Cross Compiler.
+They will typically be included in source form right after a
+stage1 binary which will interpret it on boot and bootstrap
+itself to a full intepreter, which can then be relinked with
+the Relinker. There is no loader for these libraries because
+you will typically XPACK (B267) them.
 
 422 core                       438 print
 442 fmt                        447 readln