Thanks to those who helped and advised; I discovered a problematic pin on the TU58 10-pin DIP connector. With this fixed, TU58EM worked correctly and the console code loaded. The CPU passes diags as far as the RL02 test; not surprising as there's no RL controller or drive - or the special diag pack! - installed. On a point of order... is there any reason an Emulex UCxx Unibus SCSI controller wouldn't work in this machine? Anyone with any experience there? If it emulates an MSCP disk closely it should Just Work? I'm thinking a SCSI2SD solution to give me a reliable one-box system... Mike http://www.corestore.org 'No greater love hath a man than he lay down his life for his brother. Not for millions, not for glory, not for fame. For one person, in the dark, where no one will ever know or see.'