diff --git a/Ghidra/Processors/Atmel/certification.manifest b/Ghidra/Processors/Atmel/certification.manifest
index 92392fc879..00ddbbf807 100644
--- a/Ghidra/Processors/Atmel/certification.manifest
+++ b/Ghidra/Processors/Atmel/certification.manifest
@@ -34,3 +34,5 @@ data/languages/avr8xmega.pspec||GHIDRA||||END|
 data/languages/avr8xmega.slaspec||GHIDRA||||END|
 data/manuals/AVR32.idx||GHIDRA||||END|
 data/manuals/AVR8.idx||GHIDRA||||END|
+data/patterns/AVR8_patterns.xml||GHIDRA||||END|
+data/patterns/patternconstraints.xml||GHIDRA||||END|
diff --git a/Ghidra/Processors/Atmel/data/languages/avr8.ldefs b/Ghidra/Processors/Atmel/data/languages/avr8.ldefs
index e920a37651..35a6be1fea 100644
--- a/Ghidra/Processors/Atmel/data/languages/avr8.ldefs
+++ b/Ghidra/Processors/Atmel/data/languages/avr8.ldefs
@@ -20,21 +20,21 @@
   </language>
   
   <language processor="AVR8"
+            deprecated="true"
             endian="little"
-            size="16"
+            size="24"
             variant="extended"
             version="1.4"
-            slafile="avr8e.sla"
+            slafile="avr8eind.sla"
             processorspec="avr8.pspec"
             manualindexfile="../manuals/AVR8.idx"
             id="avr8:LE:16:extended">
-    <description>AVR8 with 22-bit word addressable code space</description>
+    <description>AVR8 with 22-bit word addressable with EIND code space</description>
     <compiler name="gcc"        spec="avr8egcc.cspec"        id="gcc"/>
-    <external_name tool="gnu" name="avr:51"/>
     <external_name tool="IDA-PRO" name="avr"/>
   </language>
   
-    <language processor="AVR8"
+  <language processor="AVR8"
             endian="little"
             size="24"
             variant="atmega256"
@@ -45,6 +45,7 @@
             id="avr8:LE:16:atmega256">
     <description>AVR8 for an Atmega 256</description>
     <compiler name="gcc"        spec="avr8egcc.cspec"        id="gcc"/>
+    <external_name tool="gnu" name="avr:51"/>
     <external_name tool="gnu" name="avr:6"/>
     <external_name tool="IDA-PRO" name="avr"/>
   </language>
diff --git a/Ghidra/Processors/Atmel/data/languages/avr8egcc.cspec b/Ghidra/Processors/Atmel/data/languages/avr8egcc.cspec
index aec334bfd4..8bfbc881a7 100644
--- a/Ghidra/Processors/Atmel/data/languages/avr8egcc.cspec
+++ b/Ghidra/Processors/Atmel/data/languages/avr8egcc.cspec
@@ -38,10 +38,10 @@
   <stackpointer register="SP" space="mem" growth="negative"/>
   
   <default_proto>
-    <prototype name="__stdcall" extrapop="3" stackshift="3" strategy="register">
+    <prototype name="__stdcall" extrapop="3" stackshift="3">
       <input>
         <pentry minsize="1" maxsize="2">
-          <register name="W"/>
+          <register name="W"/>    <!-- R25R24 -->
         </pentry>
         <pentry minsize="1" maxsize="2">
           <register name="R23R22"/>
@@ -67,14 +67,11 @@
         <pentry minsize="1" maxsize="2">
           <register name="R9R8"/>
         </pentry>
-        <pentry minsize="1" maxsize="2">
-          <register name="Z"/>
-        </pentry>
-        <!-- set to 20 on purpose, so that large values don't get assigned to stack -->
-        <!-- They get allocated across register pairs, but layout algorithm too simple -->
-        <pentry minsize="24" maxsize="500" align="1">
-          <addr offset="20" space="stack"/>
-        </pentry>
+        <!-- Currently messes up parameter allocation, for known data types bigger than 2 -->
+        <!-- strategy="packreg" planned to mitigate this problem -->
+        <pentry minsize="1" maxsize="500" align="1">
+          <addr offset="4" space="stack"/>
+        </pentry>          
       </input>
       <output>
         <pentry minsize="1" maxsize="2">
@@ -126,16 +123,22 @@
     </prototype>
   </default_proto>
   
-  <prototype name="__stackcall" extrapop="3" stackshift="3" strategy="register">
+  <prototype name="__stackcall" extrapop="3" stackshift="3">
       <input>
       <pentry minsize="1" maxsize="500" align="1">
-        <addr offset="1" space="stack"/>
+        <addr offset="4" space="stack"/>
       </pentry>
     </input>
 	<output>
-	  <pentry minsize="1" maxsize="2">
-	    <register name="W"/>
-	  </pentry>
+        <pentry minsize="1" maxsize="2">
+          <register name="W"/>
+        </pentry>
+        <pentry minsize="3" maxsize="4">
+          <addr space="join" piece1="W" piece2="R23R22"/>
+        </pentry>
+        <pentry minsize="5" maxsize="8">
+          <addr space="join" piece1="W" piece2="R23R22" piece3="R21R20" piece4="R19R18"/>
+        </pentry>
 	</output>
     <unaffected>
       <register name="SP"/>
diff --git a/Ghidra/Processors/Atmel/data/languages/avr8gcc.cspec b/Ghidra/Processors/Atmel/data/languages/avr8gcc.cspec
index 162a014c4e..de40e32ee8 100644
--- a/Ghidra/Processors/Atmel/data/languages/avr8gcc.cspec
+++ b/Ghidra/Processors/Atmel/data/languages/avr8gcc.cspec
@@ -38,10 +38,10 @@
   <stackpointer register="SP" space="mem" growth="negative"/>
   
   <default_proto>
-    <prototype name="__stdcall" extrapop="" stackshift="2" strategy="register">
+    <prototype name="__stdcall" extrapop="2" stackshift="2">
       <input>
         <pentry minsize="1" maxsize="2">
-          <register name="W"/>
+          <register name="W"/>    <!-- R25R24 -->
         </pentry>
         <pentry minsize="1" maxsize="2">
           <register name="R23R22"/>
@@ -67,14 +67,11 @@
         <pentry minsize="1" maxsize="2">
           <register name="R9R8"/>
         </pentry>
-        <pentry minsize="1" maxsize="2">
-          <register name="Z"/>
-        </pentry>
-        <!-- set to 20 on purpose, so that large values don't get assigned to stack -->
-        <!-- They get allocated across register pairs, but layout algorithm too simple -->
-        <pentry minsize="24" maxsize="500" align="1">
-          <addr offset="20" space="stack"/>
-        </pentry>
+        <!-- Currently messes up parameter allocation, for known data types bigger than 2 -->
+        <!-- strategy="packreg" planned to mitigate this problem -->
+        <pentry minsize="1" maxsize="500" align="1">
+          <addr offset="3" space="stack"/>
+        </pentry>          
       </input>
       <output>
         <pentry minsize="1" maxsize="2">
@@ -126,7 +123,7 @@
     </prototype>
   </default_proto>
   
-  <prototype name="__stackcall" extrapop="3" stackshift="3" strategy="register">
+  <prototype name="__stackcall" extrapop="2" stackshift="2">
       <input>   
         <pentry minsize="1" maxsize="500" align="1">
           <addr offset="3" space="stack"/>
diff --git a/Ghidra/Processors/Atmel/data/languages/avr8iarV1.cspec b/Ghidra/Processors/Atmel/data/languages/avr8iarV1.cspec
index 2c1e32b4b6..3f14042246 100644
--- a/Ghidra/Processors/Atmel/data/languages/avr8iarV1.cspec
+++ b/Ghidra/Processors/Atmel/data/languages/avr8iarV1.cspec
@@ -15,10 +15,16 @@
  <!--   <prototype name="__stdcall" extrapop="2" stackshift="2">  -->
      <prototype name="__stdcall" extrapop="0" stackshift="0" strategy="register">
       <input>
-        <pentry minsize="1" maxsize="4">
+        <pentry minsize="1" maxsize="2">
+          <register name="R17R16"/>
+        </pentry>
+        <pentry minsize="3" maxsize="4">
           <addr space="join" piece1="R19R18" piece2="R17R16"/>
         </pentry>
-        <pentry minsize="1" maxsize="4">
+        <pentry minsize="1" maxsize="2">
+          <register name="R21R20"/>
+        </pentry>
+        <pentry minsize="3" maxsize="4">
           <addr space="join" piece1="R23R22" piece2="R21R20"/>
         </pentry>
         <pentry minsize="1" maxsize="500" align="1">
@@ -26,7 +32,10 @@
         </pentry>
       </input>
       <output>
-        <pentry minsize="1" maxsize="4">
+        <pentry minsize="1" maxsize="2">
+          <register name="R17R16"/>
+        </pentry>
+        <pentry minsize="3" maxsize="4">
           <addr space="join" piece1="R19R18" piece2="R17R16"/>
         </pentry>
       </output>
diff --git a/Ghidra/Processors/Atmel/data/patterns/AVR8_patterns.xml b/Ghidra/Processors/Atmel/data/patterns/AVR8_patterns.xml
new file mode 100644
index 0000000000..22ed12ba93
--- /dev/null
+++ b/Ghidra/Processors/Atmel/data/patterns/AVR8_patterns.xml
@@ -0,0 +1,34 @@
+<patternlist>
+
+  <patternpairs totalbits="32" postbits="16">
+    <prepatterns>
+      <data>0x08 0x95</data> <!-- ret -->
+      <data>0x18 0x95</data> <!-- reti -->
+    </prepatterns>
+    
+    <postpatterns>
+      <data>....1111 1001001. ....1111 1001001.             </data> <!-- push reg, push reg -->
+      <funcstart/>
+    </postpatterns>
+  </patternpairs>
+  
+  <pattern> <!-- 24-bit processors copy static bytes to mem -->
+      <data>
+        0x1. 0xe.                         <!-- ldi      R17,<upper> -->
+        0xa. 0xe.                         <!-- ldi      Xlo,<memlo> -->
+        0xb. 0xe.                         <!-- ldi      Xhi,<memhi> -->
+        0xe. 0xe.                         <!-- ldi      Zlo,<codelo> -->
+        0xf. 0xe.                         <!-- ldi      Zhi,<codehi> -->
+        0x0. 0xe.                         <!-- ldi      R16,<codepage> -->
+        0x0b 0xbf                         <!-- out      RAMPZ,R16 -->
+        0x02 0xc0                         <!-- rjmp     LAB_instr_next+2 -->
+        0x07 0x90                         <!-- elpm     R0,Z+ -->
+        0x0d 0x92                         <!-- st       X+,R0 -->
+        0xa. 0x3.                         <!-- cpi      Xlo,<lower> -->
+        0xb1 0x07                         <!-- cpc      Xhi,R17 -->
+        0xd9 0xf7                         <!-- brbc    inst_start-4,Zflg -->
+      </data>
+      <funcstart label="__do_copy_data"/>
+  </pattern>
+  
+</patternlist>
diff --git a/Ghidra/Processors/Atmel/data/patterns/patternconstraints.xml b/Ghidra/Processors/Atmel/data/patterns/patternconstraints.xml
new file mode 100644
index 0000000000..b785af5cd6
--- /dev/null
+++ b/Ghidra/Processors/Atmel/data/patterns/patternconstraints.xml
@@ -0,0 +1,5 @@
+<patternconstraints>
+  <language id="avr8:*:*:*">
+    <patternfile>AVR8_patterns.xml</patternfile>
+  </language>
+</patternconstraints>