Free Pascal also implements a Turbo Pascal compatibility mode. They have a porting guide: http://freepascal.org/port.var

I've been converting a large system from the 1980s from Berkeley Pascal to Free Pascal, and it's going quite well. Free Pascal implements a superset of Turbo Pascal, ISO Pascal, and Delphi. So you can revive most old Pascal code with it.

Interesting. Did you use Pascal in your networking or other work in earlier years? (Saw your profile.)

Also, there is a high-quality IDE for Free Pascal, http://www.lazarus-ide.org/.

maybe you're thinking of https://news.ycombinator.com/item?id=10202299

As https://news.ycombinator.com/item?id=10202563 said, it is not THE turbo pascal compiler.

Also there is http://www.freepascal.org/

The source is not particularly illuminating unless you really want to dig in, since it's all 16-bit x86 assembler.