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| author | H. Peter Anvin | 2008-06-27 23:29:13 +0200 |
|---|---|---|
| committer | Michael Brown | 2008-06-27 23:29:13 +0200 |
| commit | b7882065f5319d8d8f93eb4b879d816bb47bfe3a (patch) | |
| tree | 8ec8ab67ff0baf31c1580b0c7abbca5b78695042 /src/interface/pxe | |
| parent | [libc] Remove unused le32_to_cpup(x) and cpu_to_le16p() macros (diff) | |
| download | ipxe-b7882065f5319d8d8f93eb4b879d816bb47bfe3a.tar.gz ipxe-b7882065f5319d8d8f93eb4b879d816bb47bfe3a.tar.xz ipxe-b7882065f5319d8d8f93eb4b879d816bb47bfe3a.zip | |
[a20] Send a null command to the KBC after changing A20
Send a null command, specifically "pulse outputs" with no outputs
selected, to the KBC after changing A20. This was apparently done by DOS,
presumably as a synchronization hack, and the authors of the UHCI spec
thought it was inherent. Therefore, there are systems out there (e.g. HP
DL360 G5) which will stop responsing to "legacy USB" unless they see the
null command, 0xFF, written to port 0x64 at the end of the A20 toggling
sequence.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'src/interface/pxe')
0 files changed, 0 insertions, 0 deletions