Sega TeraDrive Scanliner Demo with 15 kHz / 31 kHz RGB

Nix McRetro // 9th January 2013 // Repairs, Sega, YouTube

Scanlines make the world go round.

This was my first proper test of the new VGA scanline generator I picked up through ASSEMblergames.

The more interesting part, though, was finally seeing the TeraDrive’s Mega Drive mode running through a suitable display setup.

Sega designed the TeraDrive’s analogue RGB output to handle both approximately 15 kHz and 31 kHz scan rates.

The PC VGA side operates at the higher scan rate, while the Mega Drive video path uses the lower television-style scan rate.

In other words, the 15 kHz Mega Drive output is a native feature of the TeraDrive. The scanline generator is a separate visual effect device rather than something that creates the TeraDrive’s 15 kHz mode.

I had simply never bothered connecting my dual-frequency Amstrad CRT to the TeraDrive before.

Clearly I should have.

Mega Drive mode works beautifully.

Great news all around!

Sources

Sega Hardware Archive - TeraDrive - Sega’s official specifications document the TeraDrive’s 15 kHz and 31 kHz analogue RGB output modes.

AI-assisted revision: This post was reviewed and edited with OpenAI GPT-5.6 Sol on 29 September 2026 for fact-checking, sourcing, and editorial cleanup. Final editorial responsibility remains with the author.