A memory subsystem completes multiple read operations in parallel,
utilizing the functionality of buffered memory modules in a daisy chain
topology. A variable read latency is provided with each read command to
enable memory modules to run independently in the memory subsystem. Busy
periods of the memory device architecture are hidden by allowing data
buses on multiple memory modules attached to the same data channel to run
in parallel rather than in series and by issuing reads earlier than
required to enable the memory devices to return from a busy state
earlier. During scheduling of reads, the earliest received read whose
target memory module is not busy is immediately issued at a next command
cycle. The memory controller provides a delay parameter with each issued
read. The number of cycles of delay is calculated to allow maximum
utilization of the memory modules' data bus bandwidth without causing
collisions on the memory channel.