>Hi I've just bought a D90 that will become my backup camera >when the D400 or D600 become my main camera. >I'm looking to get a couple of quality memory cards that will >be interchangeable in both cameras. >I'm wondering if a 32gig card with a 45 or 90 mb/s write speed >will work on the D90 or is this size &/or speed too much >for the older technology of the D90?
There should be no problem using the latest 32GB 95MB/sec. high speed SD cards in the D90. While the maximum write speed is limited by the camera, downloading the images from the card to your computer will be much faster than with the slower cards.
If there is a D400 I suspect that it will have a CF Card Slot as well as an SD card slot like the D300s and D800.
>Also, I almost always shoot in RAW & with a slow card >installed in the D90 can only get (r9)showing as the buffer >count remaining, will a card with a faster write speed boost >the performance of the buffer capacity at all?
The card speed will not change the Buffer Size or Capacity. Faster cards will clear the buffer faster (limited by the maximum write speed of the camera) allowing you to capture more images per unit time than if you were using a slower card. Good Luck and Enjoy your Nikons!