README.md
README.multihead
1 WARNING:
2 On exit XFree86 restores the old mode but it
3 does not disable the secondary card. As a result
4 the second card (which has some randonm CRTC timing)
5 may produce synch pulses which are wrong for your
6 monitor.
7
8 If your monitor does not tolerate bad timing I would
9 recommend that you don't try Multi-head yet, or at
10 least, turn it off *before* leaving X.
11
12
13 3.9Nl notice: There is a problem with releasing
14 of LBX colormap privates which may cause a seg.
15 fault when the server exits. I got a patch from
16 Mark Vojkovich which fixes it.
17
18 If you have a CL-GD5480 or CL-GD5446 ver. B you
19 should be able to try Multi-Head with that
20 card as a secondary. The primary card should not
21 have any special feature. Some MainBoards may
22 not do it right too. I tried it with a 5465 (AGP)
23 as a primary and 5446B (PCI) secondary on an
24 ABIT LX6 upgraded to the latest bios.
25
26 Version A of the 5446 cannot be pure MMIO (The driver
27 requires that it is the primary display adapter).
28 You can distinguish between the rel A and rel B by
29 running "scanpci -v". Version 1 does not report a
30 valid BASE1 address.
31
32 The bios upgrade lets me chose if the primary
33 display adapter is on PCI on AGP (I chose
34 the AGP card as primary). Warning - this setup
35 will *NOT* work with XFree86 3.3.2.
36
37 The only problem that I found so far is with
38 memory configuration initialization. My bios
39 does not initialize the secondary display adapter.
40 This results in a corrupted display.
41
42 Here are the options:
43 1. warm booting from Windows 98 may work. I have
44 not tried that.
45
46 2. Take out the other card and leave the 5446
47 (or 5480) as the primary card. Start the server
48 and watch it's output. Look for lines like:
49 (--) CIRRUS(0): Memory Config reg 1 is 0x1B
50 (--) CIRRUS(0): Memory Config reg 2 is 0x21
51 Remember these values. Now edit XF86Config
52 and add to the proper device section the lines:
53 Option "MemCFG1" "0x1B"
54 Option "MemCFG2" "0x21"
55 These values are the contents of registers SR0F
56 and SR17. (notice: the 5480 driver does not use
57 and will not print MemCFG2).
58
59 Now you can reinstall the other card (which
60 must me set as the the primary display adaptor).
61
62 A note about configuring multi-head:
63 There should be a separate section for each
64 adapter (device), Monitor and Screen. A "ServerLayout"
65 section is optional (and recommended). To make it
66 easier for XFree86 to relate device sections to
67 actual cards, use a BusId line in each device
68 section. XFree86 3.9N works properly if the config
69 file is for Multi-head but it finds only one
70 display adapter.
71