Hi Tech Legion posted a review on the Sapphire HD 4890 Toxic

Just the other day, I went to a friend's house to fix one of his computers since he was having a problem with his video card crashing for no specific reason. The first thing I noticed as I walked into his computer room was how much warmer it was than the rest of the house. After commenting on that and shutting off his media player I heard a high pitched whining sound coming from his case. I asked him what it was and he told me he had to keep his ZeroTherm VGA cooler at 100% or his video card would freeze. Right there I knew that heat was his issue and immediately went to check his heatsink for dust build up and to make sure that he had some decent heatsink paste on the GPU. Both were fine but he did have an older ATI card and was overclocking it.

The Sapphire HD 4890 Toxic is a preoverclcked ATI 4890, which comes with Sapphires Vapo-X heatsink and fan. The Sapphire HD 4890 Toxic is built around the ATI RV790 graphics processor which is a 55nm chip has 800
streaming processors. The Toxic is one of three overclocked versions of the HD 4890 that utilize the Sapphire Vapo-X heatsink and fan, cooling solution and it is priced in the middle of those two other cards. (Atomic and Vapo-X)

Sapphire HD 4890 Toxic Review