diff --git a/Machines/Commodore/Plus4/Plus4.cpp b/Machines/Commodore/Plus4/Plus4.cpp
index e638a3806..277cacb64 100644
--- a/Machines/Commodore/Plus4/Plus4.cpp
+++ b/Machines/Commodore/Plus4/Plus4.cpp
@@ -130,11 +130,11 @@ public:
 	ConcreteMachine(const Analyser::Static::Commodore::Target &target, const ROMMachine::ROMFetcher &rom_fetcher) :
 		m6502_(*this)
 	{
-		// PAL: 8'867'240 divided by 5 or 4?
-		// NTSC: 7'159'090?
+		// PAL: 8867240 divided by 5 or 4?
+		// NTSC: 7159090?
 		// i.e. colour subcarriers multiplied by two?
 
-		set_clock_rate(8'867'240);	// TODO.
+		set_clock_rate(7159090);	// TODO.
 
 		const auto kernel = ROM::Name::Plus4KernelPALv5;
 		const auto basic = ROM::Name::Plus4BASIC;
@@ -171,6 +171,8 @@ public:
 		const auto timers_cycles = timers_subcycles_.divide(Cycles(5));
 		timers_.tick(timers_cycles.as<int>());
 
+		video_.run_for(length);
+
 		// Perform actual access.
 		if(address < 0xfd00 || address >= 0xff40) {
 			if(isReadOperation(operation)) {
diff --git a/Machines/Commodore/Plus4/Video.hpp b/Machines/Commodore/Plus4/Video.hpp
index 86b9f1f6f..b1260ed3d 100644
--- a/Machines/Commodore/Plus4/Video.hpp
+++ b/Machines/Commodore/Plus4/Video.hpp
@@ -25,7 +25,6 @@ public:
 			);
 		};
 
-
 		switch(address) {
 			case 0xff06:
 				extended_colour_mode_ = value & 0x40;
@@ -58,6 +57,68 @@ public:
 		}
 	}
 
+	// Outer clock is [NTSC or PAL] colour subcarrier * 2.
+	//
+	// 65 cycles = 64µs?
+	// 65*262*60 = 1021800
+	//
+	// In an NTSC television system. 262 raster lines are produced (0 to 261), 312 for PAL (0−311).
+	//
+	// An interrupt is generated 8 cycles before the character window. For a 25 row display, the visible
+	// raster lines are from 4 to 203.
+	//
+	// The horizontal position register counts 456 dots, 0 to 455.
+	void run_for(Cycles) {
+		// Timing:
+		//
+		//	456 cycles/line;
+		//	if in PAL mode, divide input clock by 1.25 (?);
+		//	see page 34 of plus4_tech.pdf for event times.
+
+		// Horizontal events:
+		//
+		//	3: 38-column screen start
+		//	288: external fetch window end, refresh single clock start, increment character position end
+		//	290: latch character position to reload
+		//	296: character window end, character window single clock end, increment refresh start
+		//	304: video shift register end
+		//	307: 38-column screen stop
+		//	315: 40-column screen end
+		//	328: refresh single clock end
+		//	336: increment blink, increment refresh end
+		//	344: horizontal blanking start
+		//	358: horizontal sync start
+		//	376: increment vertical line
+		//	384: burst start, end of screen — clear vertical line, vertical sub and character reload registers
+		//	390: horizontal sync end
+		//	408: burst end
+		//	400: external fetch window start
+		//	416: horizontal blanking end
+		//	424: increment character position reload
+		//	432: character window start, character window single clock start, increment character position start
+		//	440: video shift register start
+		//	451: 40-column screen start
+
+		// Vertical events:
+		//
+		//	0: attribute fetch start
+		//	4: vertical screen window start (25 lines)
+		//	8: vertical screen window start (24 lines)
+		//	203: attribute fetch end
+		//	200: vertical screen window stop (24 lines)
+		//	204: frame window stop, vertical screen window stop (25 lines)
+		//	226: NTSC vertical blank start
+		//	229: NTSC vsync start
+		//	232: NTSC vsync end
+		//	244: NTSC vertical blank end
+		//	251: PAL vertical blank start
+		//	254: PAL vsync start
+		//	257: PAL vsync end
+		//	261: end of screen NTSC
+		//	269: PAL vertical blank end
+		//	311: end of screen PAL
+	}
+
 private:
 	bool extended_colour_mode_ = false;
 	bool bitmap_mode_ = false;
@@ -76,6 +137,9 @@ private:
 	uint16_t character_row_address_ = 0;
 	uint16_t character_generator_address_ = 0;
 	uint16_t screen_memory_address_ = 0;
+
+	int horizontal_counter_ = 0;
+	int vertical_counter_ = 0;
 };
 
 }