First, I found out that both the problematic alphas had memory compaction and
page migration and bounce buffers turned on, and working alphas had them off.
Next, turing off these options makes the problematic alphas work.
OK, thanks for testing! Can you narrow down whether the problem is due to
CONFIG_BOUNCE or CONFIG_MIGRATION + CONFIG_COMPACTION? These are two
completely different things so knowing where to look will help. Thanks!