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- Quick DDR2 memory question
- Amir Facade
February 11, 2007, 5:25 am
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Re: Quick DDR2 memory question
Amir Facade wrote:
Grab a datasheet for one and have a look. This one advertises
operation at both DDR2-800 and DDR2-667. And the clock
specification tells you, in fact, that slower operation
is also possible.
One difference between DDR2-800 memory and the slower ones,
is the DDR2-800 chips have one additional ODT programming
option. AFAIK, that doesn't stop them from being used
in slower applications. In the pictures here, you can
see there are three switchable options for ODT, shown in
the block diagram for the RAM (figure 5, page 15). Presumably
all those options are needed, for backward compatibility.
In general, the memory specs are intended to encourage
backward compatibiility with slower products.