Calculating the Checksum

[Ross Myers]

After my recent experience in disabling the VATS check, I am now wondering
how the Checksum is calculated.

For the VATS it was kinda easy, as the disable signal ment taking 10h off
$0014, then taking 10h off the checksum bytes $0006 & $0007 (This is the
same address for 88 & 89 Vette isn't it?, anyway it worked, no code 51, and
checksum was still enabled).

But lets say I change lots of values, what bytes get left out of the
checksum value?. I know you don't add all of them up, so where?

Is it the same address' for all chips used in the same ECM?.

Thanks

Ross Myers