Although the Radeon HD 4850 X2 is an official SKU by AMD, launched (rather paper-launched) by the company along with the HD 4870 X2, Sapphire ended up being the only company to come up with an HD 4850 X2 series product line, since AMD didn't specify a reference design of its own. Sapphire went on to launch 1GB (2x 512MB) and 2GB (2x 1GB) variants of the said accelerator. In AMD's latest release of the Catalyst driver suite (version 9.1), the HD 4850 X2 was excluded from the supported hardware list. Instead the company now released a special release of Catalyst 9.1 for the Radeon HD 4850 X2 series. The driver provides the same feature-set and list of fixes as described in the original release notes document for Catalyst 9.1, albeit being specific for the said accelerator. The WHQL-signed drivers are available for Windows Vista and Windows XP operating systems from the AMD website here.