This exam tips covers Exam Tips - MAR and MDR within MAR, MDR & Registers for GCSE Computer Science. Revise MAR, MDR & Registers in 3.4 Computer Systems for GCSE Computer Science with 15 exam-style questions and 10 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 7 of 8 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Exam Tips - MAR and MDR
The golden rule:
- MAR = Address = WHERE = Address Bus
- MDR = Data = WHAT = Data Bus
Common mistakes to avoid:
- Mixing up MAR and MDR - this loses ALL marks for that question!
- Forgetting which bus each connects to
- Saying MAR holds data or MDR holds addresses
Top tip: If you're ever unsure, think "Address before Data" - MAR works first (says where), then MDR receives the result (the data).
Practice questions for MAR, MDR & Registers
What does MAR stand for?
Explain the difference between the MAR and the MDR.
Quick recall flashcards
What does MAR hold?
The address of data to be read/written (WHERE)
What does MDR hold?
The actual data being transferred (WHAT)