Rīmu-x does not appear in the "standard" version of the Assyrian King List [/riao/kinglists/assyriankinglist/index.html#Section5-7] (AKL), nor are any inscriptions of this monarch known. As such, his exact position is subject to much debate. Rīmu-x's name is partially preserved in a fragment of a different version of the AKL, VAT 9812 [/riao/kinglists/fragmentvat9812/index.html#List]. Here he is listed along with Mut-Aškur and possibly also Asīnum (Landsberger 1954, 42-43). If this is the case, then he may have been a member of the Samsī-Addu Dynasty. Julian Reade suggests that Rīmu-x was the ruler at Ekallātum, and that Asīnum may have been his governor at Aššur, or another member of Samsī-Addu's family who was a contemporary of Rīmu-x in Aššur (Reade 2001, 6). Reade also remarks that Irving Finkel has suggested that a-sí-nim may correspond to the noun assinnu (priest of Ištar). If this is the case, Reade states that assinnu may have been a nickname for Rīmu-x and that Asīnum and Rīmu-x may consequently be the same person (ibid). Gashe et al. support the theory that Mut-Aškur and his successors ruled in Ekallātum as part of the Samsī-Addu Dynasty (Gasche et al. 1998, 52). They suggest, however, that these kings ruled during approximately the same period that Aššur-dugul and his successors occupied the throne in Ashur.
Poppy Tushingham
Poppy Tushingham, 'Rīmu-x', RIA 1: Inscriptions from the Origins of Assyria to Arik-dīn-ili, The RIA Project, 2023 [http://oracc.org/oldassyrianperiod/samsiaddudynasty/rimux/]