The 925 is to the 915 what the 875 was to the 865, that is to say a chipset specifically engineered to give tweaked memory.Source: The Inquirer
The additional memory tweaks on the 925 make it an expensive option for motherboard firms and for end users.
Most of the Taiwanese manufacturers will, however, focus on Grantsdale chipsets first and then add Alderswood platforms later, but some of the big name boys will have both ready for launch.
As some of these big boys make Intel branded motherboards for Chipzilla itself, this is not that surprising.
"Intel's 925 continues having problems - launch to be delayed?"

According to The Inq there are some problems with Intel's 925 chipset, which would make Intel unable to launch this chip on the 21st of this month.