Editing Motorola 68020 (section)

== Architecture ==
{| class="infobox" style="font-size:88%;width:39em;"
|-
|+ Motorola 68020 registers
|-
|
{| style="font-size:88%;"
|-
| style="width:10px; text-align:left"  | <sup>3</sup><sub>1</sub>
| style="width:60px; text-align:center"| ...
| style="width:10px; text-align:right" | <sup>2</sup><sub>3</sub>
| style="width:60px; text-align:center"| ...
| style="width:10px; text-align:center"| <sup>1</sup><sub>5</sub>
| style="width:60px; text-align:center"| ...
| style="width:10px; text-align:center"| <sup>0</sup><sub>7</sub>
| style="width:60px; text-align:center"| ...
| style="width:10px; text-align:center"| <sup>0</sup><sub>0</sub>
| style="width:auto; background:white; color:black" | ''(bit position)''
|-
|colspan="10" | '''Data registers'''
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D0
| style="background:white; color:black" | Data 0
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D1
| style="background:white; color:black" | Data 1
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D2
| style="background:white; color:black" | Data 2
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D3
| style="background:white; color:black" | Data 3
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D4
| style="background:white; color:black" | Data 4
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D5
| style="background:white; color:black" | Data 5
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D6
| style="background:white; color:black" | Data 6
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| D7
| style="background:white; color:black" | Data 7
|-
|colspan="10" | '''Address registers'''
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A0
| style="background:white; color:black" | Address 0
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A1
| style="background:white; color:black" | Address 1
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A2
| style="background:white; color:black" | Address 2
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A3
| style="background:white; color:black" | Address 3
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A4
| style="background:white; color:black" | Address 4
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A5
| style="background:white; color:black" | Address 5
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A6
| style="background:white; color:black" | Address 6
|-
|colspan="10" | '''Stack pointers'''
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A7 / USP
| style="background:white; color:black;"| Stack&nbsp;Pointer (user)
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| A7' / SSP
| style="background:white; color:black;"| Stack&nbsp;Pointer (supervisor)
|-
|colspan="10" | '''Program counter'''
|- style="background:silver;color:black"
| style="text-align:center;" colspan="9"| PC
| style="background:white; color:black;"| Program&nbsp;Counter
|}
|-
|
{| style="font-size:88%;"
|-
|colspan="17" | '''Condition Code Register'''
|-
| style="width:98px; text-align:center"| &nbsp;
| style="width:10px; text-align:center"| <sup>1</sup><sub>5</sub>
| style="width:10px; text-align:center"| <sup>1</sup><sub>4</sub>
| style="width:10px; text-align:center"| <sup>1</sup><sub>3</sub>
| style="width:10px; text-align:center"| <sup>1</sup><sub>2</sub>
| style="width:10px; text-align:center"| <sup>1</sup><sub>1</sub>
| style="width:10px; text-align:center"| <sup>1</sup><sub>0</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>9</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>8</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>7</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>6</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>5</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>4</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>3</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>2</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>1</sub>
| style="width:10px; text-align:center"| <sup>0</sup><sub>0</sub>
| style="width:auto; background:white; color:black" | ''(bit position)''
|- style="background:silver;color:black"
| style="background:white;"| &nbsp;
| style="text-align:center" colspan="2"| T
| style="text-align:center"| S
| style="text-align:center"| M
| style="text-align:center"| 0
| style="text-align:center" colspan="3"| I
| style="text-align:center"| 0
| style="text-align:center"| 0
| style="text-align:center"| 0
| style="text-align:center"| X
| style="text-align:center"| [[Sign flag|N]]
| style="text-align:center"| [[Zero flag|Z]]
| style="text-align:center"| [[Overflow flag|V]]
| style="text-align:center"| [[Carry flag|C]]
| style="background:white; color:black" | '''CCR'''
|}
|}

{{See also|Motorola 68000 series#Architecture}}
With full 32-bit internal and external address buses, the address registers (A0 through A7) could utilize their full 32-bit width, and were capable of addressing the entire 4&nbsp;GB address space.

The larger effective widths of the address registers presented some problem for earlier software that was not considered "[[32-bit clean]]". Some programs used the high 8 bits (bits 24-31) of addresses to contain various flag bits, with the understanding that the earlier 680x0 CPUs would safely ignore these high bits. Such software had to be rewritten to adjust to the larger physical address space available to the 68020 and later CPUs.