For the IEEE 1394 FireWire 400 standard, what are the typical maximum bus speed and maximum number of devices supported on a single bus segment?

Introduction / Context:
FireWire, also known as IEEE 1394, is a high speed serial bus standard that was widely used for connecting digital video cameras, external drives and other multimedia devices. The FireWire 400 version was one of the most common implementations. Understanding its basic specifications, such as maximum signaling speed and maximum device count per bus segment, is useful in hardware and computer engineering courses that compare peripheral interconnect technologies like USB, FireWire and modern high speed buses.

Given Data / Assumptions:

We are focusing on the IEEE 1394a FireWire 400 standard, not FireWire 800 or later variants.
The question asks for the typical maximum bus bandwidth in megabits per second and the maximum number of devices that can coexist on a single FireWire bus segment.
The answer choices mention speeds such as 12 Mb/s, 400 Mb/s, 480 Mb/s and higher, and different device counts.
We assume standard, textbook level values rather than vendor specific implementation limits.

Concept / Approach:
FireWire 400 supports signaling rates of up to 400 megabits per second, which is why it is commonly called FireWire 400. The IEEE 1394 architecture uses a tree like topology that allows multiple devices to be connected without a host centric hub requirement. Each bus segment can address up to 64 unique node IDs, but one of these IDs is reserved. Therefore, up to 63 active devices can typically be attached to a single FireWire bus. These fundamental numbers, 400 Mb/s and 63 devices, are standard values found in reference material for FireWire 400.

Step-by-Step Solution:
Step 1: Recall that FireWire 400 is formally known as IEEE 1394a with a maximum signaling rate of 400 Mb/s for the highest speed mode. Step 2: Identify that the architecture allows up to 64 addresses for nodes on a bus, numbered 0 through 63, but at least one address is used for special purposes, which leaves a maximum of 63 general devices. Step 3: Compare this understanding with the answer options. The option that states 400 Mb/s and 63 devices matches these well known specifications. Step 4: Confirm that other options correspond to different standards, such as USB 1.1, USB 2.0 or entirely unrealistic values.

Verification / Alternative check:
If you consult standard technical references about IEEE 1394a, you will see that three signaling rates are defined: S100 at 98.304 Mb/s, S200 at 196.608 Mb/s and S400 at 393.216 Mb/s, commonly rounded and referred to as 100, 200 and 400 Mb/s. FireWire 400 supports all three and is normally described as providing up to 400 Mb/s. References also state that the addressing scheme allows up to 64 nodes, with practical implementations allowing up to 63 connected devices plus the host. This confirms the correctness of the selected option.

Why Other Options Are Wrong:
12 Mb/s and 32 devices aligns more with older USB 1.1 speeds rather than FireWire 400 specifications.
480 Mb/s and 127 devices is commonly associated with USB 2.0, not with FireWire 400, and uses a different topology and protocol.
10 Gb/s and unlimited devices is not realistic for the legacy FireWire standard and greatly exceeds its defined capabilities.

Common Pitfalls:
Students sometimes confuse FireWire specifications with USB specifications because both were used for external storage and multimedia. Another pitfall is to treat the maximum theoretical bandwidth as always achievable in practice, ignoring protocol overhead and bus sharing. It is also important to remember that maximum device count refers to addressable devices on a bus, which may be constrained by power delivery and cabling limits in real systems.

Final Answer:
For FireWire 400, the bus supports up to 400 Mb/s of signaling speed and up to 63 devices on a single bus segment.