i'm sorry to triple post but i was reading down farther in the graphics rules.sgr file and look at what i found out about ATI cards (this is copied straight out of the file):
# The Radeon series has a very slow path for partial
# depth buffer copies. This has apparently been
# fixed for 9500 and later models in the latest drivers,
# but cannot be fixed on previous Radeons because of
# hardware limitations.
# NOTE: disabling this rule unnecessarily may lead to
# very poor graphics performance.
partialRule "Radeon"
stringMatch cardIdentity "*Radeon*"
partialRule "SlowSubrectDepthCopy" -any
stringMatch cardIdentity "*7?00*"
stringMatch cardIdentity "*8?00*"
stringMatch cardIdentity "*9000*"
stringMatch cardIdentity "*9100*"
stringMatch cardIdentity "*9200*"
stringMatch cardIdentity "*9300*"
stringMatch cardIdentity "*9400*"
stringMatch cardIdentity "ATI, Radeon"
stringMatch cardIdentity "ATI, Radeon VE"
stringMatch cardIdentity "ATI, Radeon Mobility"
stringMatch cardIdentity "ATI, Radeon FireGL"
# results in special low-impact scrolling mode.
property noPartialBackingStoreCopies true
# try to reduce the number of dirty rects.
property dirtyRectMergeFrames 8
# use black and white cursors. The Radeons seem
# to work with colour for a while, but in low
# memory situations revert to flickering.
option $Cursor $CursorBW