Originally posted by: MarcVenice
1000MHz isn't gauranteed. I have two HD4890's from Asus to play with, and in crossfire the max they would do was 975MHz/4400mhz, but I did have to up the voltage for that. Afaik 925MHz/4400MHz was highest stable on stock voltage. I haven't extensively tested a single HD4890 with an overclock though, was going to do so later this week. What I do know is that I hit 950MHz/4400MHz on stock volts, but 1000MHz/4400MHz would lock up the hard blue way. Will be adding some voltage and see if I can hit 1000MHz, but not all HD4890's can have their voltage raised so easily. So bottom line, 1000MHz isn't gauranteed. Here's the screenshot of 975MHz btw:
http://tweakers.net/ext/i/1239028555.jpeg
Also, the HD4890 is significantly faster then a HD4780 1GB, but for it to be worth $100 you really have to OC it. What I can tell from the games I've benched, is that the HD4890 doesnt suddenly give playable framerates where a HD4870 1GB does not. It could probably give smoother gameplay though.