3640 has reached end of sale status. Last date of ordering it was in 2002 Nov. As an alternative, to customers, 3640A was released. Its identical to the 3640 in terms of hardware configuration, hardware support, memory, IOS feature set etc. The only difference lies, in the supported IOS release, which starts on the 3640 with a 12.0(24). All the T train IOS es are supported on the 3640 and 3640A.(even the 12.3). The software support will continue until 2005.
So there is no need to upgrade from 3640 to 3640A, as its basically the same hardware.
Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus
