On Lion DP1-4 installations, after using sleep and wake in the system normally, BIOS reports CMOS Checksum Error on reboot or boot after shutdown. It seems that the new AppleRTC.kext v1.4 added functionatality is causing this Error.
Initially, a workaround suggested by JUN Ho is to use the AppleRTC.kext from SnowLeopard
Then by blocking a few jumps and calls in the procedures of AppleRTC.kext, the Checksum Error was overcome. It appears APPLE has left in-situ much of their realtime testing code in this kext and these modifications do not apparently affect their basic functionatility in normal cases.
On further investigation by tseug and with the assistance of his DumpCMOS.kext , an updated patch (post# 217) was prepared by blackosx. This patch for vanilla AppleRTC.kext is effective on the latest build 11A494a. (besides also on recent builds)
This solution will not affect those osx86 setups which inherently have Sleep or Wake problems. However, it will overcome the CMOS Checksum Error caused by RTC register length of 0x04 or 0x08 in DSDT and eliminate log msg RTC: Only single RAM bank (128 bytes) if, when a RTC register length of 0x02 is used.
Added 2nd day of July, 2011
New patch for AppleRTC.kext of Lion GM - Build 11A511 by tseug (Post #248). The binary patch now, is a single unconditional jump for each arch to bypass Checksum changes.
Added 10th day of July, 2011
An alternate patch for AppleRTC.kext of Lion GM. (Post # 340)
sudo perl -pi -e 's|\x75\x30\x44\x89\xf8|\xeb\x30\x44\x89\xf8|; s|\x75\x3d\x8b\x75\x08|\xeb\x3d\x8b\x75\x08|' /System/Library/Extensions/AppleRTC.kext/Contents/MacOS/AppleRTCComment 1st day of Septemebr, 2011
You may wish to put the patched kext in E/E and leave the Vanilla kext in S/L/E alone.
October 24th, 2011 - Above patch reportedly good for 10.7.2 too.