System configuration :

- radeon 9000 AGP ( M9, rv250 )
- laptop pentium 4 2.4 Ghz 1.25 Gb ram
- archlinux 32 bits

Step to reproduce the bug

- mesa 8.0.4 release ( but the bug occurs also with the git version )
- a graphic card who uses the r200 driver 
- install piglit ( git version )
- run the glean test "blendFunc" in piglit :

./piglit-run.py  -t "glean/blendFunc" tests/quick.tests results/quick

the glean/blendFunc will fail with these error messages :

First failing pixel is at row 11 column 24
Actual values are (0, 0, 0, 0.54902)
Expected values are (0, 0, 0, 0.557007)
Errors are (0, 0, 0, 0.00798696)
Source values are (0.462745, 0.756863, 0.662745, 0.546639)
Destination values are (0.819608, 0.0980392, 0.615686, 0.0509804)
blendFunc:  FAIL rgba8, db, z24, s8, win+pmap, id 33
	source factor RGB = GL_ZERO, source factor A = GL_ONE_MINUS_DST_COLOR
	dest factor RGB = GL_ZERO, dest factor A = GL_CONSTANT_COLOR
	equation RGB = GL_FUNC_ADD, equation A = GL_FUNC_ADD
	const color = { 0.25, 0, 1, 0.75 }
	Readback had 0 bits in error; blending had 1.03186 bits in error.

First failing pixel is at row 7 column 27
Actual values are (0.682353, 0.682353, 0.92549, 0.756863)
Expected values are (0.682353, 0.682353, 0.92549, 0.765417)
Errors are (0, 0, 0, 0.0085544)
Source values are (0.682353, 0.968627, 0.243137, 0.761929)
Destination values are (0.682353, 0.682353, 0.92549, 0.0156863)
blendFunc:  FAIL rgba8, db, z24, s8, win+pmap, id 33
	source factor RGB = GL_ZERO, source factor A = GL_ONE_MINUS_DST_COLOR
	dest factor RGB = GL_ONE, dest factor A = GL_ONE_MINUS_DST_ALPHA
	equation RGB = GL_FUNC_ADD, equation A = GL_FUNC_ADD
	const color = { 0.25, 0, 1, 0.75 }
	Readback had 0 bits in error; blending had 1.13088 bits in error.

First failing pixel is at row 1 column 16
Actual values are (0.0705882, 0.298039, 0.243137, 0.74902)
Expected values are (0.0693272, 0.296286, 0.245752, 0.756865)
Errors are (0.00126106, 0.00175321, 0.00261439, 0.00784552)
Source values are (0.909804, 0.694118, 0.0784314, 0.804654)
Destination values are (0.768627, 0.968627, 0.266667, 0.0784314)
blendFunc:  FAIL rgba8, db, z24, s8, win+pmap, id 33
	source factor RGB = GL_ZERO, source factor A = GL_ONE_MINUS_DST_COLOR
	dest factor RGB = GL_ONE_MINUS_SRC_COLOR, dest factor A = GL_ONE_MINUS_SRC_ALPHA
	equation RGB = GL_FUNC_ADD, equation A = GL_FUNC_ADD
	const color = { 0.25, 0, 1, 0.75 }
	Readback had 0 bits in error; blending had 1.00608 bits in error.