Graphics chip giants ATI and nVidia have spent the past 18 months proving how resourceful they can be, with a slew of 'new' chips consisting of little more then a rejigging of existing technology. The new ATI Radeon HD 4890 doesn't totally adhere to the 'as before, but slightly faster' blueprint - but it's certainly close.
The Sapphire ATI Radeon HD 4890 is built around a RV790 core, in essence a bigger and better version of the RV770 that powered the 4850 and 4870. And that's literally bigger, since, in a departure from the usual tactic of shrinking the chip (meaning less heat and allowing higher speeds), the RV790 is actually marginally larger.
The Sapphire ATI Radeon HD 4890 is still created using the 55nm manufacturing process, but the number of transistors has increased from 956 to 959 million.
Sapphire has chosen to run with the standard clock speeds for this first rendition of the HD 4890, and so the Sapphire ATI Radeon HD 4890 comes with core and memory clocks of 850MHz and 975MHz respectively, beating those of a standard HD 4870 by 100MHz and 75MHz.
In many other respects, the Sapphire ATI Radeon HD 4890 is very similar to the 4870. This Sapphire 4890 comes with 1GB of RAM - and, as with the 4870 and 4850, this is in the form of the superior GDDR5 type, so allowing the 4890 to partially compensate for the restricted 256-bit memory bus.
And copying the RV770 cards, the Sapphire ATI Radeon HD 4890 has 800 stream processors and support for DirectX 10.1 rather than the more ubiquitous 10.0 found in nVidia's range. We've seen little necessity of DirectX 10.1 so far, but the support is there should games programmers start making use of the slight enhancements offered.
The Sapphire ATI Radeon HD 4890 isn't a dramatic leap in performance over the 4870. It is, though, a slight improvement, generally adding between 3 and 8% to the scores tallied by the tried and tested 4870 cards. It clears the tuned-up HIS HD 4870 IceQ 4+ by several frames in most tests, while managing to cost only slightly more.