[Bug 39282] radeon HD6790 (barts) card produces black+white horizontal stripes on screen when launching Xorg

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=39282

--- Comment #37 from Florian Evers <florian-evers at gmx.de> 2011-12-12 08:22:52 PST ---
Hi Alex,

today I searched the web to find some specs regarding the BARTS LE chipset of
the HD 6790 cards. I found three references that contain useful information:

http://ht4u.net/reviews/2011/amd_radeon_hd_6790_barts_le_im_test/index2.php

http://www.nordichardware.com/news/71-graphics/42743-exclusive-radeon-hd-6790-based-on-barts-le-with-800-sps.html

http://www.tomshardware.de/Radeon-HD6790-Test-Benchmark-Review,testberichte-240757-2.html

I collected all useful specs and can give you a summary now. For a Radeon HD
6790 with BARTS LE, these specs are given:

Stream processors (Vec5): 160
Shader ALUs: 800 = 160*Vec5
Shader type: Vec5 (Co Issue 1:1:1:1:1)
Capabilities per Shader: MADD
Double Precision: no
Texture Units (TMUs): 40
Raster Operation (ROP): 16
Shader Model Version: 5.0
DirectX 11
Output: 2 Render Backends (instead of 4), with 8 ROPs each

SIMD-Cluster (Streaming Multiprocessor) "SM-Units": 10
per SIMD-Cluster: 16 Vec5 ALUs

Per SIMD-Cluster: 1 Quad-TMU (=4 TMUs), 40 in total


If I look at the patched file evergreen.c, I see that the specs do not match
yet. For example, the number of SIMDS is defined as 5 in the source, but the
references tell me that the BARTS LE has 10.

Additionally, I tried 3.2-rc5 today, showing the same does-not-boot behavior as
before. However, setting num_ses to "1" makes sense in terms of calculating
max_backends as num_ses * 2, as the BARTS LE has only 2 backends available.
Unfortunately, it doesn't work here with a setting of "1" for num_ses.

I can't assign the other variables in the source code, as I have no idea what
"max_pipe", "max_tile_pipes" and other statements such as the famous
"backend_map" mean...

Hope you can correct some of the settings? :-)

Regards,
Florian

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