diff --git a/scu-dsp/advent/2020/day1/runner.m4.asm b/scu-dsp/advent/2020/day1/runner.m4.asm
new file mode 100644
index 0000000..b51bb74
--- /dev/null
+++ b/scu-dsp/advent/2020/day1/runner.m4.asm
@@ -0,0 +1,16 @@
+        ;;
+        ;; transfer to vdp2
+        ;;
+
+        ;; vdp2 address calculation
+        mvi ((8 * 0x4000 + (64 - 8) * 4 + 0x05e00000) >> 2),wa0
+                                   mov 0,ct3
+        ;;                 clr a      mov 0,ct3
+        ;; add             mov alu,a
+        ;;                            mov all,wa0
+
+        ;; end vdp2 address calculation
+        dma1 mc3,d0,8
+dma_wait:
+        jmp t0,dma_wait
+        nop
diff --git a/scu-dsp/lib/div10_unsigned.asm b/scu-dsp/lib/div10_unsigned.asm
new file mode 100644
index 0000000..083afb9
--- /dev/null
+++ b/scu-dsp/lib/div10_unsigned.asm
@@ -0,0 +1,34 @@
+        ;;
+        ;; function: div10_unsigned
+        ;;
+
+        ;; argument: ry
+        ;; return: a ← ry / 10
+        ;; maximum ry is somewhere between 2 ^ 21 and 2 ^ 22
+div10_unsigned:
+        ;; 1 / 10 * (2 ^ 24) ~= 1677722 = 0x19999a
+        mvi 1677722,rx
+             mov mul,p  clr a
+        ad2             mov alu,a
+
+        ;;   ALH: [nmlkjihgfedcba9876543210________]
+        ;;   ALL: [76543210________________________]
+
+                        clr a      mov alh,pl ; alh is (a >> 16)
+        add             mov alu,a
+
+        ;;   ALL: [nmlkjihgfedcba9876543210________]
+
+        ;; rotate left 24 requires fewer cycles than shift right 8
+        rl8             mov alu,a
+        rl8             mov alu,a
+        rl8             mov alu,a
+
+        ;;   ALL: [________nmlkjihgfedcba9876543210]
+
+        ;; mask 24 bit result
+        mvi 0xffffff,pl
+
+        ;; return to caller ; reset ct0
+        btm
+        and             mov alu,a  mov 0,ct0
diff --git a/scu-dsp/lib/unparse_base10.asm b/scu-dsp/lib/unparse_base10.asm
new file mode 100644
index 0000000..970fc2d
--- /dev/null
+++ b/scu-dsp/lib/unparse_base10.asm
@@ -0,0 +1,57 @@
+        ;;
+        ;; inline function: unparse_base10
+        ;;
+
+        ;; argument: m2[0]
+        ;; return: base10 + 16 in m3[56 - 63]
+
+        ;; requires: div10_unsigned
+
+unparse_base10:
+        ;; clear end of m3
+        mov (64 - 8),ct3
+        mov 7,lop
+        lps
+        mov 0,mc3
+        mov (64 - 8),ct3
+
+        ;; output: m3
+unparse_base10_loop:
+                                   mov 0,ct2
+        mvi div10_unsigned,pc
+        ;;   [X     ]   [Y     ]   [D1     ]
+                        mov mc2,y  mov 1,lop     ; mvi imm,pc delay slot (executed twice)
+        ;; after function return:
+                                   mov all,mc0   ; m0[1] (1234)
+                                   mov all,pl
+        ;; mod10: multiply by 10:
+        sl              mov alu,a
+        sl              mov alu,a
+        sl              mov alu,a
+        add             mov alu,a
+        add             mov alu,a  mov 0,ct0     ; restore ct0 after 'mov all,mc1'
+
+        ;;   a: 12340
+                        mov mc0,a  mov all,pl
+
+        ;;   a: 12345   m0[0]
+        ;;   p: 12340
+
+        ;; mod10: subtract (a - p)
+        sub             mov alu,a  mov 16,pl
+
+        ;;   a: 5
+
+        ;; convert to vdp2 character
+        add             mov alu,a
+
+        ;; store digit in m3
+             mov mc0,p  clr a      mov all,mc3   ; m0[1]
+
+        ;;   p: 1234
+        ;;   a: 0
+        add             mov alu,a  mov 0,ct0
+
+        ;;   a: 1234
+        jmp nz,unparse_base10_loop
+                                   mov all,mc0   ; jmp delay slot