Everything about JVC Professional 4KCAM camcorders all on one page:

Buyer’s Guide: JVC Professional 4KCAM and ProHD Camcorders at DV Info Net (http://www.dvinfo.net/article/buyers_guides/buyers-guide-jvc-4kcam-and-prohd-camcorders.html)

-- instruction manual downloads
-- press release and product page links
-- comparison chart and individual descriptions
-- product support page links & firmware download links
-- prices and "where to buy" from DV Info Net sponsors

Models covered are:

GY-HM620

GY-HM660

GY-HM850

GY-HM890

(and to a small degree, the JY-HM360)