diff --git a/CONFIG.md b/CONFIG.md
index e74d85bb..cd3ba26a 100644
--- a/CONFIG.md
+++ b/CONFIG.md
@@ -289,6 +289,12 @@ On the most widespread CPUs the D flag is not cleared upon entering interrupts.
 
 Feature needs 2 bytes in KERNAL segmment (for CPUs needing the patch), but at the same time allows optimizations allowing to gain some more bytes. If unsure - enable.
 
+### `ARNITECH_CONTROLLER`
+
+For the mc64 computers of arnitech only, whose expansion port holds the Arnitech controller at `$DE80`. IOINIT puts CIA #1's TOD on 50 Hz and, if the controller's signature `"ARNI"` is at `$DE80`, sets the TOD from the controller's clock. The Arnitech jump table at `$FF00` (`src/kernal/arnitech/ff00.arnitech_jumptable.s`) wraps the controller's registers.
+
+Feature needs about 120 bytes in KERNAL segment, and the page at `$FF00`. Disable on any other machine.
+
 ## Eye candy
 
 ### `COLORS_BRAND`
diff --git a/Makefile b/Makefile
index 343b39a4..477724c6 100644
--- a/Makefile
+++ b/Makefile
@@ -45,6 +45,7 @@ SRCDIR_KERNAL  = $(SRCDIR_COMMON) \
                  src/kernal \
                  src/kernal/,stubs \
                  src/kernal/assets \
+                 src/kernal/arnitech \
                  src/kernal/board_crt \
                  src/kernal/board_m65 \
                  src/kernal/board_u64 \
diff --git a/src/,,config_mc64.s b/src/,,config_mc64.s
index 867a4d03..82d23fc8 100644
--- a/src/,,config_mc64.s
+++ b/src/,,config_mc64.s
@@ -10,6 +10,8 @@
 ; Same as the 'c64' configuration, except:
 ; - the banner names mc64
 ; - BCD_SAFE_INTERRUPTS is off, for IRQ entry timing closer to the original
+; - ARNITECH_CONTROLLER: IOINIT sets CIA1's TOD on 50 Hz and from the Arnitech controller's clock,
+;   and the Arnitech jump table is at $FF00 (src/kernal/arnitech)
 
 
 
@@ -103,6 +105,7 @@
 ;; #CONFIG# TAPE_WEDGE                 NO
 ;; #CONFIG# TAPE_HEAD_ALIGN            NO
 ;; #CONFIG# BCD_SAFE_INTERRUPTS        NO
+;; #CONFIG# ARNITECH_CONTROLLER        YES
 
 
 ; --- BASIC features
diff --git a/src/aliases/,aliases_hardware_arnitech.s b/src/aliases/,aliases_hardware_arnitech.s
new file mode 100644
index 00000000..ef5f1366
--- /dev/null
+++ b/src/aliases/,aliases_hardware_arnitech.s
@@ -0,0 +1,26 @@
+
+;
+; Names of the Arnitech controller's registers, on the expansion port's I/O1 (mc64 only)
+;
+; See arnitech's ADR 0023, "The Arnitech controller answers $DE80-$DE9F, and six Card windows
+; follow it" (https://git.susdog.de/chris/arnitech, docs/adr/0023-arnitech-controller-register-map.md)
+;
+
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+	!addr ARNITECH_SIGNATURE   = $DE80  ; "ARNI", 4 bytes
+	!addr ARNITECH_VERSION     = $DE84
+	!addr ARNITECH_SLOT_COUNT  = $DE85  ; Card slots in this Case
+	!addr ARNITECH_IRQ_STATUS  = $DE86
+	!addr ARNITECH_IRQ_MASK    = $DE87
+	!addr ARNITECH_SLOT_TABLE  = $DE88  ; the type of the Card in slots 0-5, $00 for none
+
+	!addr ARNITECH_CLOCK_LATCH = $DE90  ; a read copies the clock into $DE91-$DE9E
+	!addr ARNITECH_CLOCK_TEN   = $DE91  ; real time as CIA1's TOD reads it: tenths,
+	!addr ARNITECH_CLOCK_SEC   = $DE92  ; seconds,
+	!addr ARNITECH_CLOCK_MIN   = $DE93  ; minutes,
+	!addr ARNITECH_CLOCK_HRS   = $DE94  ; hours, BCD 1-12, bit 7 PM
+
+	!addr ARNITECH_CARD_WINDOW = $DEA0  ; slot n's Card window at $DEA0 + 16 * n
+}
diff --git a/src/kernal/arnitech/arnitech_controller.s b/src/kernal/arnitech/arnitech_controller.s
new file mode 100644
index 00000000..a69e31ae
--- /dev/null
+++ b/src/kernal/arnitech/arnitech_controller.s
@@ -0,0 +1,64 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; The Arnitech controller (mc64 only, arnitech's ADR 0023): its signature and its Slot table
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+;
+; Whether the controller answers: its signature "ARNI" at $DE80, compared with the jump table's.
+; Out: carry clear if it does, carry set if not. A and X are not kept, Y is.
+;
+
+arnitech_check_signature:
+
+	ldx #$03
+@1:
+	lda ARNITECH_SIGNATURE, x
+	cmp arnitech_jumptable, x
+	bne @2
+	dex
+	bpl @1
+
+	clc
+	rts
+@2:
+	sec
+	rts
+
+;
+; ARNI_FINDCARD, $FF06: see ff00.arnitech_jumptable.s
+;
+
+arnitech_find_card:
+
+	pha
+	jsr arnitech_check_signature
+	pla
+	bcs @2                             ; no controller
+
+	ldx #$00
+@1:
+	cpx ARNITECH_SLOT_COUNT
+	bcs @2                             ; past the last slot, carry set
+	cmp ARNITECH_SLOT_TABLE, x
+	beq @3
+	inx
+	bne @1                             ; always taken
+@2:
+	rts
+@3:
+	txa
+	pha
+	asl
+	asl
+	asl
+	asl                                ; 16 * slot
+	clc
+	adc #<ARNITECH_CARD_WINDOW
+	tax
+	pla
+	rts                                ; carry clear
+}
diff --git a/src/kernal/arnitech/arnitech_tod.s b/src/kernal/arnitech/arnitech_tod.s
new file mode 100644
index 00000000..4bfddfcc
--- /dev/null
+++ b/src/kernal/arnitech/arnitech_tod.s
@@ -0,0 +1,58 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; CIA1's TOD from the Arnitech controller's real time (mc64 only, arnitech's ADR 0023)
+;
+; The controller lays its time out as the TOD reads it, so the copy goes hours first, which stops
+; the TOD, and tenths last, which starts it. The CIA flips the PM bit when an hour of 12 is
+; written (VICE does so too), so an hour of 12 has bit 7 flipped first.
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+;
+; ARNI_SETTOD, $FF09: see ff00.arnitech_jumptable.s
+;
+
+arnitech_set_tod:
+
+	lda CIA1_CRA
+	ora #$80                           ; TOD on 50 Hz, the mc64's mains
+	sta CIA1_CRA
+
+	; FALLTHROUGH
+
+;
+; The copy alone, for IOINIT, which has set CRA already.
+; Out: carry clear if set, carry set if no controller answers. A and X are not kept, Y is.
+;
+
+arnitech_tod_from_clock:
+
+	jsr arnitech_check_signature
+	bcs @2
+
+	lda ARNITECH_CLOCK_LATCH           ; copies the clock into $DE91-$DE9E
+
+	ldx ARNITECH_CLOCK_HRS
+	txa
+	and #$7F
+	cmp #$12
+	bne @1
+	txa
+	eor #$80                           ; the CIA flips it back
+	tax
+@1:
+	stx CIA1_TODHRS                    ; stops the TOD
+	lda ARNITECH_CLOCK_MIN
+	sta CIA1_TODMIN
+	lda ARNITECH_CLOCK_SEC
+	sta CIA1_TODSEC
+	lda ARNITECH_CLOCK_TEN
+	sta CIA1_TODTEN                    ; starts it
+
+	clc
+@2:
+	rts
+}
diff --git a/src/kernal/arnitech/ff00.arnitech_jumptable.s b/src/kernal/arnitech/ff00.arnitech_jumptable.s
new file mode 100644
index 00000000..f57b4ce7
--- /dev/null
+++ b/src/kernal/arnitech/ff00.arnitech_jumptable.s
@@ -0,0 +1,40 @@
+;; #LAYOUT# STD *        #TAKE
+;; #LAYOUT# *   *        #IGNORE
+
+;
+; The Arnitech jump table (mc64 only): thin wrappers over the Arnitech controller's registers
+; (arnitech's ADR 0023), at fixed addresses. Software finds it by reading "ARNI" at $FF00 with
+; the KERNAL banked in; on any other KERNAL it uses the registers themselves, which work the same.
+; Entries are only ever added, after the last, with the version and count raised; $FF48-$FF80
+; stay clear, for the stock IRQ entry, CINT, and the KERNAL revision byte.
+;
+; $FF00-$FF03  "ARNI"
+; $FF04        version of the table, $01
+; $FF05        number of entries
+;
+; $FF06  ARNI_FINDCARD - finds the first Card slot holding a Card of a given type
+;        In:  A = the Card's type ($01 Redstone Card, $02 Internet Card; $00 finds an empty slot)
+;        Out: carry clear if found: A = the slot (0-5), X = the low byte of its Card window
+;             ($DEA0 + 16 * slot, so LDA $DE00,X reads the window's first byte);
+;             carry set if no slot holds one, or no controller answers (a Cartridge switched it off)
+;        Y is kept; A and X are not, when none is found
+;
+; $FF09  ARNI_SETTOD - sets CIA1's TOD from the controller's real time, as IOINIT does at boot
+;        In:  nothing; CIA1's CRB bit 7 must be 0, or the time goes into the TOD alarm
+;        Out: carry clear if set: the TOD on 50 Hz (CIA1 CRA bit 7) and started at the time the
+;             controller's clock latch read; carry set if no controller answers, with the TOD
+;             untouched but on 50 Hz all the same
+;        A and X are not kept, Y is
+;
+
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+arnitech_jumptable:
+
+	!byte $41, $52, $4E, $49           ; "ARNI"
+	!byte $01                          ; version
+	!byte $02                          ; entries
+
+	jmp arnitech_find_card             ; $FF06
+	jmp arnitech_set_tod               ; $FF09
+}
diff --git a/src/kernal/init/fda3.ioinit.s b/src/kernal/init/fda3.ioinit.s
index 70851e0d..5a3ba439 100644
--- a/src/kernal/init/fda3.ioinit.s
+++ b/src/kernal/init/fda3.ioinit.s
@@ -168,8 +168,18 @@ IOINIT_skip_DOS:
 	jsr setup_irq_timer
 
 	; Enable timer A to run continuously (http://codebase64.org/doku.php?id=base:timerinterrupts)
+!ifdef CONFIG_ARNITECH_CONTROLLER {
+
+	; ... with the TOD on 50 Hz, the mc64's mains, set from the Arnitech controller's clock
+	ldx #$91
+	stx CIA1_CRA     ; $DC0E
+	jsr arnitech_tod_from_clock
+
+} else {
+
 	ldx #$11
 	stx CIA1_CRA     ; $DC0E
+}
 
 	; Enable timer interrupt
 	ldx #$81