Floating point cost on embedded systems in Embedded C - Step-by-Step Execution

Concept Flow - Floating point cost on embedded systems

Start Program

↓

Perform Floating Point Operation

↓

Check Hardware Support?

No→Use Software Emulation

↓

More CPU Cycles

↓

Execute in Hardware

↓

Increased Power & Time

↓

Result Ready

↓

End Program

The program performs floating point operations, which run faster if hardware support exists; otherwise, software emulation causes more CPU cycles and power use.

Execution Sample

Embedded C

float a = 1.5f;
float b = 2.5f;
float c = a * b;
// Multiply floats on embedded system
// Check cost in CPU cycles

This code multiplies two floating point numbers on an embedded system, showing the cost difference with or without hardware support.

Execution Table

Step	Operation	Hardware Support	CPU Cycles Used	Power Consumption	Result
1	Load a=1.5	Yes	1	Low	a=1.5
2	Load b=2.5	Yes	1	Low	b=2.5
3	Multiply a*b	Yes	5	Low	c=3.75
4	Result ready	Yes	0	Low	c=3.75
5	Load a=1.5	No	10	High	a=1.5
6	Load b=2.5	No	10	High	b=2.5
7	Multiply a*b (software)	No	100	High	c=3.75
8	Result ready	No	0	High	c=3.75

💡 Execution stops after result is ready; hardware support reduces CPU cycles and power use.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7	After Step 8
a	undefined	1.5	1.5	1.5	1.5	1.5	1.5	1.5	1.5
b	undefined	undefined	2.5	2.5	2.5	undefined	2.5	2.5	2.5
c	undefined	undefined	undefined	3.75	3.75	undefined	undefined	3.75	3.75

Key Moments - 3 Insights

Why does the CPU cycle count jump from 5 to 100 when hardware support is missing?

Without hardware support, floating point operations use software emulation, which takes many more CPU cycles as shown in steps 3 vs 7 in the execution_table.

Does the result value change between hardware and software multiplication?

No, the result 'c=3.75' is the same in both cases (steps 4 and 8), but the cost in CPU cycles and power differs.

Why is power consumption higher without hardware support?

Software emulation uses the CPU longer, increasing power use as shown in the 'Power Consumption' column for steps 5-8.

Visual Quiz - 3 Questions

Look at the execution_table, how many CPU cycles does the hardware multiply operation take?

A 5

B 10

C 100

D 1

💡 Hint

Check the 'CPU Cycles Used' column at step 3 for hardware multiplication.

At which step does software emulation perform the multiplication?

A Step 5

B Step 3

C Step 7

D Step 8

💡 Hint

Look for 'Multiply a*b (software)' in the 'Operation' column.

If hardware support is present, what is the power consumption during multiplication?

A High

B Low

C Medium

D None

💡 Hint

Refer to the 'Power Consumption' column for steps 1-4.

Concept Snapshot

Floating point operations on embedded systems
- Hardware support runs faster and uses less power
- Without hardware, software emulation is slow and costly
- CPU cycles and power use increase significantly without hardware
- Result values stay the same, cost differs
- Important to consider for battery-powered devices

Full Transcript

This visual execution shows how floating point multiplication runs on embedded systems with and without hardware support. When hardware support exists, the CPU uses fewer cycles and less power (steps 1-4). Without it, software emulation takes many more cycles and more power (steps 5-8). The result value remains the same, but the cost in time and energy is higher without hardware. This helps understand why floating point operations can be expensive on small devices.