As it happens I was involved in the investgation of a Swissair MD-80 which had had smoke in the cockpit. It came from a short in the emergency power switch - directly fed from the battery through an inaccessible (in the cellar) 80AH circuit breaker - which didn't pop.
After a light start, the smoke built up so fast, that they couldn't read the check list - couldn't see to depressurise and open a panel (the removal procedure) and just about got it down in MUC by waving the smoke away with the checklist.
They then saw that the windows were covered in quite thick ash inside.
I hope that SAS ship gets a good long check over before they let it fly again.
FC.