MBps

from The Free On-line Dictionary of Computing (8 July 2008)

megabits per second
mbps

   <unit> (Mbps, Mb/s) Millions of {bits} per second.  A unit of
   {data rate}.  1 Mb/s = 1,000,000 bits per second (not
   1,048,576).

   E.g. {Ethernet} can carry 10 Mbps.

   (2002-03-23)

from The Free On-line Dictionary of Computing (8 July 2008)

megabytes per second
MBps

   <unit> (MBps, MB/s) Millions of {bytes} per second.  A unit of
   {data rate}.  1 MB/s = 1,000,000 bytes per second (not
   1,048,576).

   (2007-02-20)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

MBPS
       MegaBits Per Second (BIT)

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