diff --git a/README.md b/README.md
index 121d98f..a6b97c1 100644
--- a/README.md
+++ b/README.md
@@ -16,15 +16,16 @@ The only part of this I don't quite understand is that 16 bytes from slot 1 don'
 
 ## ROM layout
 
+The first 16KB of the ROM (regardless of old vs. new) is just directly mapped to C000-FFFF ROM. INTCXROMON must be enabled to access Cxxx, of course. This is the same as the CF ROM of a Platinum IIe, or CD+EF ROMs concatenated from an earlier IIe.
+
+The second 16KB of the ROM contains slot and option ROM for the built-in peripherals. The exact mapping varies between the two models.
+
 ### "Old" Laser 128
 
 ```
 0000 - 00FF = empty (reserved for soft switches)
-0100 - 07FF = C100-C7FF (INTCXROMON)
-0800 - 0FFF = C800-CFFF slot 1 option ROM (INTCXROMON)
-1000 - 1FFF = D000-DFFF ROM
-2000 - 2FFF = E000-EFFF ROM
-3000 - 3FFF = F000-FFFF ROM
+0100 - 0FFF = C100-CFFF (INTCXROMON)
+1000 - 3FFF = D000-FFFF ROM
 4000 - 40FF = empty (reserved for soft switches)
 4100 - 42FF = C100-C2FF (INTCXROMOFF, Parallel mode)
 4300 - 43FF = empty (no ROM for slot 3)
@@ -49,11 +50,8 @@ Slot 6 option ROM bank 2 is empty in ROM 2.9, but it might be populated on other
 
 ```
 0000 - 00FF = empty (reserved for soft switches)
-0100 - 07FF = C100-C7FF (INTCXROMON)
-0800 - 0FFF = C800-CFFF slot 1 option ROM (INTCXROMON)
-1000 - 1FFF = D000-DFFF ROM
-2000 - 2FFF = E000-EFFF ROM
-3000 - 3FFF = F000-FFFF ROM
+0100 - 0FFF = C100-CFFF (INTCXROMON)
+1000 - 3FFF = D000-FFFF ROM
 4000 - 40FF = empty (reserved for soft switches)
 4100 - 47FF = C100-C7FF (INTCXROMOFF, SLOTC3ROMON)
 4800 - 4FFF = C800-CFFF Slot 1 option ROM (INTCXROMOFF)
diff --git a/src/DUMPROM.s b/src/DUMPROM.s
index 5d72821..6bac16a 100644
--- a/src/DUMPROM.s
+++ b/src/DUMPROM.s
@@ -89,15 +89,8 @@ loop:   sta     base,y
         ; $0000 - $1fff, common to old and new models
 com0:   fillff  $2000,0             ; $C000-C0FF empty (soft switches)
         sta     INTCXROMON
-        mv      $2100,$c100,$c7ff   ; $C100-C7FF from main ROM
+        mv      $2100,$c100,$cfff   ; $C100-C7FF from main ROM
         sta     INTCXROMOFF
-
-        lda     $cfff
-        lda     $c100
-        sta     INTCXROMON
-        mv      $2800,$c800,$cfff   ; slot 1 option ROM alternate
-        sta     INTCXROMOFF
-        lda     $cfff
         fillff  $2ff8,8
 
         mv      $3000,$d000,$dfff   ; D000-DFFF ROM
@@ -120,19 +113,16 @@ new4:   fillff  $2000,0             ; $C000-C0FF empty (soft switches)
         lda     $cfff
         lda     $c100
         mv      $2800,$c800,$cfff   ; slot 1 option ROM
-        lda     $cfff
         fillff  $2ff8,8
 
         lda     $cfff
         lda     $c500
         mv      $3000,$c800,$cfff   ; slot 5 option ROM
-        lda     $cfff
         fillff  $37f8,8
 
         lda     $cfff
         lda     $c200
         mv      $3800,$c800,$cfff   ; slot 2 option ROM
-        lda     $cfff
         fillff  $3ff8,8
 
         rts
@@ -166,7 +156,6 @@ new6:   s7bank  #$00
         lda     $cfff
         lda     $c600
         mv      $3800,$c800,$cfff   ; slot 6 option ROM
-        lda     $cfff
         fillff  $3ff8,8
 
         rts
@@ -183,7 +172,6 @@ old4:   fillff  $2000,0             ; $C000-C0FF empty (soft switches)
         lda     $cfff
         lda     $c100
         mv      $2800,$c800,$cfff   ; slot 1 option ROM
-        lda     $cfff
         fillff  $2ff8,8
 
         fillff  $3000,0             ; empty
@@ -197,7 +185,6 @@ old4:   fillff  $2000,0             ; $C000-C0FF empty (soft switches)
         lda     $cfff
         lda     $c200
         mv      $3800,$c800,$cfff   ; slot 2 option ROM
-        lda     $cfff
         fillff  $3ff8,8
 
         rts
@@ -221,7 +208,6 @@ old6:   fillff  $2000,0             ; empty
         lda     $c600
         lda     $c100
         mv      $2800,$c800,$cfff   ; slot 6 option ROM bank 1
-        lda     $cfff
         fillff  $2ff8,8
 
         fillff  $3000,0             ; empty
@@ -237,7 +223,6 @@ old6:   fillff  $2000,0             ; empty
         lda     $c600
         lda     $c200
         mv      $3800,$c800,$cfff   ; slot 6 option ROM bank 2
-        lda     $cfff
         fillff  $3ff8,8
 
         rts