VR-Zone reports that ATI's R520 will probably only have 16 pipelines as the yield rates are really terrible. The 90nm R520 is produced at TSMC and according to VR-Zone's sources it only has a 3 percent yield rate for 24 pipes and the yield rate for 32 pipes is even much worse.
This means if ATI wants to launch the R520 in August-September they will need to launch a R520 with only 16 pipelines. If they really want to keep on with a 24-32 pipes part then the R520 may be delayed till the fourth quarter of this year.
Obviously ATi is still facing some yield issues for their R520 @ 90nm process and ATI could resort to a 16 pipes R520 for better yield and make up the loss with a much higher core clock of 700MHz+ as INQ has previously suggested.