There is an SRM for the 164LX. I don't think its available in the newer
firmware releases but I have a copy from around v5.0. There isn't enough
flash space to have both SRM and AlphaBIOS loaded at the same time, so
switching is painful. Apart from that it works quite well.
It's also available in the current firmware release (was an SRM firmware
ever dropped from newer firmware releases?), e.g. on Gatekeeper: