Pixel clock
The pixel clock is how many pixels per second a video signal carries. 4K60 needs 594 MHz; the Vertex handles up to 600 MHz.
The pixel clock is how many pixels are sent every second, counted in megahertz (MHz, millions per second).
Think of a conveyor belt with one pixel on each tray: the pixel clock is how fast the belt runs. Bigger pictures and more pictures per second need a faster belt, and every cable and device has a top speed.
What pixel clock can the HDfury Vertex handle?
HOW IT WORKSUp to 600 MHz (18 Gbps). That fits 4K60 4:4:4 8-bit and 4K60 4:2:2 12-bit (594 MHz). 4K60 4:4:4 10-bit would need 742.5 MHz, so it does not fit.
How to use it with the Vertex:
- Read the TMDS clock of each signal on the OLED Info page, e.g. '594MHz' (p.19).
- The RX INFO page shows both values, e.g. 'PCLK 296.97MHz TMDS 445.46MHz' (p.19).
- The GUI top section shows bandwidth for each input and output (p.27).
- For a 300 MHz display, use Auto Scaling presets that convert to 300 MHz formats (p.14, p.30).
What it is
A video timing contains more than the visible picture: there are invisible blanking pixels around it. The pixel clock counts all of them. Standard examples: 1080p60 uses 148.5 MHz, 4K30 uses 297 MHz and 4K60 uses 594 MHz.
On HDMI 2.0, what really has to fit is the TMDS clock, which also depends on color format. Deep color raises it: 10-bit needs 1.25× and 12-bit 1.5× the 8-bit value. 4:2:0 halves it. 4:2:2 always uses the same rate as 8-bit, even at 12-bit. HDMI 2.0 tops out at 600 MHz (18 Gbps).
That is why 4K60 HDR on HDMI 2.0 is sent as 4:2:2 12-bit or 4:2:0 10/12-bit: 4K60 4:4:4 at 10-bit would need 742.5 MHz, which is more than 600.
On the Vertex
The Vertex handles signals up to 600 MHz, enough for 4K60 4:4:4 8-bit and 4K60 4:2:2 12-bit (p.5, p.110). The OLED info page shows the clock of each signal, for example "4K59.94 422 BT2020 12b HDR 594MHz". The RX INFO page shows both values, for example "PCLK 296.97MHz TMDS 445.46MHz" for a 4K60 4:2:0 12-bit signal (p.19).
The manual uses the pixel clock as a unit of time too: the delay the Vertex adds is "in the order of a few pixel clocks only", which is far less than a millisecond (p.104).
Common questions
Why does my Vertex show 594 MHz and not 600 MHz?
594 MHz is the standard clock for 4K60. 600 MHz is the maximum the Vertex and HDMI 2.0 can carry, so 594 MHz fits.
Why can't I get 4K60 4:4:4 10-bit HDR through HDMI 2.0?
It would need 742.5 MHz, above the 600 MHz limit. HDR at 4K60 is sent as 4:2:2 12-bit or 4:2:0 instead.
Is pixel clock the same as refresh rate?
No. Refresh rate is pictures per second (Hz); the pixel clock is pixels per second (MHz), and depends on resolution and refresh rate together.