AMD has decided to switch some of its older Radeons, from the 9000 series through the X1000 series, into what is calls "legacy" support status. The move means those GPUs will no longer be included in the monthly Catalyst graphics driver drops. Instead, for the time being, they'll receive driver updates (mainly centered on bug fixes) on a quarterly basis.
Here's a list of the older GPUs (both discrete and integrated) that will be affected by the change:
On the workstation front, AMD will also move to quarterly releases for X-series, Z-series, V3100-V3400, V5000-V5200, and V7100-V7350 FireGLs, as well as the FireMV 2200 and 2250.
AMD justifies the change by saying that the drivers for older GPUs should already be quite refined, and it argues that more recent monthly Catalyst updates have offered minimal returns for those products, either in the form of bug fixes or performance improvements. The firm expects this move to free up resources so it can concentrate on development of new drivers for current and future products for current and future operating systems.
If you're curious about how the competition handles things, Nvidia continues to support circa-2004 GeForce 6-series graphics cards in its regular driver releases. However, Nvidia doesn't officially stick to a monthly release schedule, so updates can be comparatively more sporadic.