I applied for this job almost two years ago, when I graduated as an MSc in Micro-electronics Design with distinction.
First, they will give you a telephone interview and ask some simple questions such as digital circuit design stuff. Then they need you to do an on-line test before you go to the assessment centre.
ARM head-quarter has this assessment centre for graduates every month in order to hire the talented into the company. After arrival at 8:00 they will briefly give introduction of the company by the head of R&D. Then one senior engineer would show you some clever designed machine base on Logo mind-storm kit and arm processor that solves magic cube automatically, essentially to make promotion for arm processor.
Then group interview starts. In my case they put candidates in group of 4, asking them to discuss and design an app (from back-end to front-end) for travel. Then the group is asked to present the work in front of all. There're senior guys from a mixture of departments following up the performance of each candidate from start to finish.
The second round group interview starts after tea break, and in my case we are assigned into group of 4-5 people (different from the previous one) to design the algorithm for some race car (again based on arm processor), and then the car is put on to a track that has sensor for timing. Nothing else is provided except an Lenovo Thinkpad with Internet connection, the race car, and the interconnection cod. To win this round, the 4 or 5 of candidates need to collaborate really well. It's best for the candidates to search from the Internet of the coding style, rather than to start everything from scratch. Besides, collaboration is definitely needed. Although possible, it is not recommended that one man single-handedly finish the research-design-test phase. The goal is better to be accomplished through division of labour because this is the time to show both your talent and your teamwork. Similar to the last round, senior guys from different departments will follow up the performance of each candidate from start to finish.
Lunch is provided at noon (Dominos pizza), and there are single tech-interviews for each candidate.Each candidate is picked up by two (or one) senior engineers from the target department and the venue of the interview is typically in the departments building. In my case the interview was more like a chat and I was briefing my MSc project (the front-end to back-end design of a RISC processor) to two senior guys. Occasionally they would ask questions to the detail of the project, and some basic questions on microprocessor design as well. The interview last for 2 hrs, and during the interview you will also go through a quiz on digital VLSI design (HDLs, timings, systems etc).
As a summary, as an international student in the U.K., whether you're hired or not really doesn't depends on whether you're good enough but on whether they have the spare places for work visa and whether the department you apply really needs new blood. In my case, I managed to answer all (most, if not all) the questions in the tech interview and our group ranks the first in the race car competition. After nearly 4 months I got an rejection (man if you don't want to hire me please give me the notice earlier. It is a shame if you just keep me waiting until someone from uk or eu who fits this role showed up) . By the time when the rejection letter arrived, I had long started as a PhD student. On the contrary, another student from local who applied for a software position got the offer immediately(3 days after the interview), despite the fact that he couldn't answer most of the questions. So who knows what these large companies are thinking.