In a a short spacewalk just under three hours two astronauts today successfully replaced the failed MDM data relay unit on the outside of ISS.
Some additional details about this unit:
The MDM that failed and an identical unit are part of the tier 2 command architecture and relay commands to a variety of critical station systems, including the station’s guidance, navigation and control system, the lab’s stabilizing gyros, the environmental control system, the station’s cooling system and others.
Both tier 2 computers were installed during spacewalks March 30 and March 24 respectively, replacing two older units with models featuring upgraded data processing cards. It is not yet known whether the problem with MDM-1 involved the upgraded components or some other circuitry or software
I suspect this upgraded but failed unit is going to be looked at very carefully.