I could help to test the firmware radeon, my tc6 x86 is up to date. But my hardware is an old ATI X1400 mobile. Please send me your tcz. Regards.
X.Org X Server 1.17.1
Release Date: 2015-02-10
[ 21.989] Build Operating System: Linux 3.16.6-tinycore i486
[ 21.989] Current Operating System: Linux box 3.16.6-tinycore #777 SMP Thu Oct 16 09:42:42 UTC 2014 i686
[ 21.989] Kernel command line: initrd=/boot/6/core.gz tce=sda3/tce6-32 blacklist=pcspkr keymap=azerty/fr-pc BOOT_IMAGE=/boot/6/vmlinuz
[ 21.989] Build Date: 13 February 2015 05:30:32PM
[ 22.011] (II) LoadModule: "radeon"
[ 22.011] (II) Loading /usr/local/lib/xorg/modules/drivers/radeon_drv.so
[ 22.029] (II) Module radeon: vendor="X.Org Foundation"
[ 22.029] compiled for 1.17.1, module version = 7.5.0
[ 22.054] (--) RADEON(0): Chipset: "ATI Mobility Radeon X1400" (ChipID = 0x7145)
[ 22.054] (II) Module "dri2" already built-in