In the old days or with small chips, the system level designer used to request the whole system be created before the design is started. Back in the day the Analog designer did everything including layout. Having one guy do everything sounds great but is basically uncompetitive since its serial and non interactive. (You may believe your own bullshit) I have met a few fans of the serial approach, they tend to be older than I am defensive, and have low self esteem. A good chip design program should be able to survive if any member disappears, including the lead. There may be a delay but the chip goes on.
I call the "show must go on" approach to integrated circuit (IC) design "Infinite Mass". This term was coined by a mentor of mine, the late Dave Nack. Dave used this expression to describe the management style used on him in a bad way. Dave Nack was my manager at the time and didn't like being told how to manage analog. He told me that pushing back on good solid analog technique was like "Stopping Jupiter in its path".
Infinite mass is all about project momentum. This can be an asset or a
weapon. Once you get your team assembled and start the Micro
architecture specifications(MAS), you begin to solicit input from the
different experts on your team (specific to the task). Having different people work in
parallel in the definition stage builds a relationship between the
people and the product. Micro-management is the enemy here. Relationships foster dedication and encourage quality. The Micro-architecture spec completion
is a key milestone, even if it has a few blank pages or tables. It
becomes a cornerstone of the chip and its often a living document since
things are discovered during the development. The MAS eventually should contain key details of all the blocks
You can't push back against infinite mass. At some point after the MAS is defined and the project is underway, each sub-block needs to go through its own architectural phase. During this time the system is in flux since the analog or digital may not be possible without devastating results. The team needs to be open to marketing input before the architecture is closed. However, after the MAS is basically closed, basically the "cooks are in the kitchen" and things need to be stable otherwise they wont finish. This type of "Infinite Mass" design puts huge pressure on marketing and product definition. The bigger the chip, the longer marketing has before the architecture is closed. However, once its closed it should be difficult to change, with "chip death" one of the options. A late change in the game could take the whole chip from compelling to crap.
Two killers of SOCs that I know of are:
1. Unanticipated Collateral Consequence of Change (UCCC): Complex systems can break in subtle ways. Late in the game a change could "look ok" but cause pathology that may be hard to detect before the chip comes back. I remind non-analog people that each transistor has at least 4 connections: Drain, Gate, Source,Bulk. If your design has, say 100,000 transistors, then you have 400,000 connections. If you change any one, it could affect the others. The change needs to be carefully executed. The later you go in the project, the more of the connections are "made", therefore increasing the risk of change while increasing verification. Its actually more complicated than this simple example, which leads to the second killer
#2. Underestimation of the complexity of the task at hand: (UCTAH) This assumes that the thing you don't know about is easy to solve or doesn't matter. This is big for people who like to assume things or think they know it all. One hidden killer in optical sensors is the package. Delivering a reliable part that detects light in reasonably cheap package is very challenging. You can have the best circuit designer in the world but he won't help make your part survive the re-flow soldering process. The answer to UCTAH is honest feedback and a good relationships with peers in your field. When in doubt, get on the phone and ask a few people you trust. If you find your understanding of the situation lacking, maybe you have UCTAH.
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