Eochy I Buide reigned 608-629, The surname Boyd is said to derive from his name. He is also called King of the Picts.

The system of succession to kingship amongst the Scots differed from the one we follow today. Now, our monarchs are chosen by a hereditary system known as primogeniture: generally, the eldest son of a deceased king succeeds to the throne. Primogeniture is relatively straightforward, but has the disadvantage of sometimes resulting in minorities, which occur whenever the heir to the throne is too young to fulfil his duties. A regency has to be established until the king comes of age, and this often produces political instability. The Scots, in contrast, followed the Celtic law of tanistry. Tanistry requires that a brother or cousin of the king be nominated by him as his successor. Thus, the throne tends to pass between different branches of the royal family. The advantage of this system is that there is always a mature king on the throne. The disadvantage, as the Scots learned throughout their history, is that it sometimes leads to assassination and to warfare between competing claimants to the throne.
Amongst the kings of Dalriada, the succession alternated between the descendants of Erc, with those of Fergus dominating. In fact, after Loarn, the kingship did not pass to this branch of the family until Ferchar Fota, who died in 697. Two sons, and then two grandsons of Ferchar Fota came to the throne, but after this it remained firmly in the hands of the descendants of Fergus. At the time of Ferchar Fota's reign, Dalriada was a weakened kingdom; the throne was fleetingly held by the various claimants, and the Scots were dominated by the Picts. Only Selbach of the Tribe of Loarn had a long reign of twenty-three years.