This page deals with the MacBook Pro 13" and the MacBook Aluminium.
In October 2008 Apple announced a new addition to its MacBook line, with the MacBook Aluminium. This was a considerably higher end (and more expensive) than the white and black MacBooks and Apple continued to sell a white MacBook at a cheaper price.
The Aluminium MacBook is much closer to contemporary MacBook Pros than to other MacBooks, using faster DDR3 PC3-8500 memory and having a similar Aluminium unibody case. However it did not have an ExpressCard expansion slot, and controversially did not have any sort of FireWire connection, relying on USB 2 for connectivity. This Mac was sold with a 2GHz or 2.4GHz CPU. Apple's own specifications for the October 2008 MacBook Aluminium can be found here.
In June 2009 Apple updated the machine, and changed the name to the MacBook Pro 13", bringing it into the Pro range which it had always been closer to than the consumer-targeted MacBooks.
The first MacBook Pro 13" is a similar machine to the
MacBook Aluminium. Maximum memory capacity increases from
6GB to 8GB, a FireWire 800 port and an SD memory card slot
were added. It does not have an ExpressCard expansion slot.
It was sold with a 2.26GHz or 2.53GHz CPU. Apple specs here.
In April 2010 the MacBook Pro 13" was updated with faster
processor options (2.4GHz or 2.66GHz) and better graphics processing.
Compatibility of upgrades remains unchanged. Apple specs here.
The line was refreshed in February 2011. The CPU was moved
to either a dual Core i5 2.3GHz or a dual Core i7 2.7GHz. The
graphics chip was upgraded and the new Thunderbolt connection
was added. Importantly for upgrades, the memory was updated
to PC10600 (DDR3 1333MHz) and the machine can take up to 16GB
RAM in 2 x 8GB modules. Apple specs here.
In October 2011 a minor update was released with CPU speed
options increased to either a dual Core i5 2.4GHz or a dual
Core i7 2.8GHz. The graphics card was also updated. Compatibility
of upgrades remains unchanged. Apple specs here.
In June 2012 a new model was released with either a 2.5GHz
dual i5 or 2.9GHz dual i7 CPU.
The RAM was upgraded to DDR3 PC2800 1600MHz, with a maximum
of 16GB in 2 x 8GB modules. Other upgrades remain unchanged
Apple specs here.
A "Retina" display model was released in October 2012 with
a very high-resolution display was launched, however RAM and
hard drives are fixed in the retina models and non-upgradeable
specs on the retina models are here.
The previous non-retina model continued to be sold with the
same capability for upgrades.
An updated non-upgradeable "Retina" model was released
in February 2013. Apple specs here.