I don't know about other Universities but for NTU, you can find out more here:
[1] A-Levels:
http://admissions.ntu.edu.sg/UndergraduateAdmissions/Pages/ALevel.aspx
[2] Polytechnic Diploma:
http://admissions.ntu.edu.sg/UndergraduateAdmissions/Pages/PolyDiploma.aspx
For Polytechnic, Diploma Result: 80% and O-Level: 20%.
I believe it's more towards comparing your result with other applicants and if your Diploma result is on an even level, then your O-level result comes into play to decide the weightage.
Some subjects are also rated higher based on the applied course requirements.
Originally posted by Killerjazz:I an just curious about the requriement of university.
Do they see O level result?
If they got, do they accept student with D7 in O level in english or math?
They will ask you to re-take your "O" level English and to get a pass in it and re-apply the next year.