This is that thread.
Also, the diagram was wrong.
TX and RX have been swapped.
To make myself extremely clear - if you follow the diagram, you should connect the pin labelled TX in the diagram to the TX pin of your "computer" (I think we're all using USB-TTL UARTs these days).
This is the reverse to how one would normally do thing - i.e. connecting the TX of device A to the RX of device B.
I will also add, (because this was bugging me aswell), that it will work without any jumpers being set (i.e. the master jumper, which inconveniently shares the ground pin), and without a 40-pin connector.
Apply power to the drive, set serial port to 9600 8-n-1 (no flow control) and you should see this on bootup.
Interface task reset 4096k x 16 buffer detected ALPINE - 1_Disk M-21 11-25-03 18:53 Buzz - Buzz - Head Mask FFFF - Switch to full int. Spin Ready 8.54 09-29-04 10:54 (P)PATA Reset CE Log EC=0 Rtype=36 OV=0 STStatus0 Slave
I would assume this apples to other PATA Seagate drives, YMMV.