tvp_source_setup() disables the TVP7002 internal H-PLL coast for every
PC-type preset. That is right for RGBHV, but with sync-on-green or
composite sync the serration pulses during vsync disturb the H-PLL every
frame; on a NeXTstation Color (1120x832, SoG) this caused continuous
horizontal jitter, jitter in the top third of the picture and a periodic
HDMI re-sync. With the option on, coast is re-enabled after setup when the
sync source is SOG or CSYNC; RGBHV is untouched. Default Off, so existing
behaviour is unchanged. Stored as profile item id 68.
On the NeXT, this option together with the existing settings Analog sync
LPF = 10 MHz, ADC PLL BW = Low and H-PLL Pre/Post-Coast = 4/4 ran 19
minutes without a sync loss, mode re-program or IT6613 video-stable
change. SPARCstation 20 framebuffers (ZX, TurboGX) over composite sync are
stable without it.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WiXHy7Jhh5yTdsBaenucgw
