Polycom SOUNDPOINT SIP 3.1 - Manual (Page 301)

Miscellaneous Administrative Tasks
C - 9
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BootROM/SIP Application Dependencies
Not withstanding the hardware backward compatibility mandate, there have
been times throughout the life of the SoundPoint IP / SoundStation IP phones
where certain dependencies on specific bootROM and application versions
have been necessitated.
This table summarizes some the major dependences that you are likely to
encounter:
Migration Dependencies
In addition to the bootROM and application dependencies, there are certain
restrictions with regard to upgrading or downgrading from one bootROM
release to another bootROM release. These restrictions are typically caused by
the addition of features that change the way bootROM provisioning is done,
so the older version become incompatible.
Model BootROM SIP Application
IP 301/501 2.6.1 or later 1.4.2, 1.5.4, 1.6.1 or
later
IP 320/330 3.2.3 B or later 2.1.1 or later
IP 430 3.1.3 C or later 1.6.6 or later
IP 550 3.2.2 B or later 2.1 or later
IP 560 4.0.1 or later 2.2.2 or later
IP 600 2.0 or later 1.0 or later
IP 601/EM 3.1 or later 1.6 or later
IP 650/EM 3.2.2 B or later 2.0.3 B or later
IP 650/BEM 4.0.1 or later 2.2.2 or later
IP 670/CEM 4.1.1 or later 3.0.3 or later
IP 4000 3.1.2 or later 1.4 or later
IP 6000 4.1.1 or later 3.0.2 or later
IP 7000 4.1.1 or later 3.0.2 or later