CRC Time Calculator

Inputs

Data size

Enter a positive value.

Unit

Select a unit.

Packet count

Use 1 for a single file or stream chunk.

Must be at least 1.

CRC width

Mode

Choose your CRC execution path.

Overhead (µs)

Setup, DMA, call overhead, interrupts, etc.

CPU frequency (MHz)

Use measured average clock if scaling occurs.

Cycles per byte

Default updates with mode and width.

Parallel workers

Threads, cores, or independent lanes.

Throughput (Mb/s)

CRC engine streaming rate or bus-limited rate.

Parallel lanes

Independent CRC engines or widened datapaths.

Notes

Example Data

Scenario	Data	Mode	Core/Rate	Assumption	Typical use
Firmware update	64 MB, 1 packet	Table-driven	800 MHz, 10 cycles/byte	Overhead 200 µs	Image integrity checks
High-speed link	1500 bytes, 10,000 packets	Hardware	10,000 Mb/s, 1 lane	Overhead 20 µs	Ethernet CRC at line rate
Microcontroller loop	4 KB, 64 packets	Bitwise	120 MHz, 90 cycles/byte	Overhead 10 µs	Small tables, minimal memory
Multi-core batch	1 GB, 1 packet	Table-driven	3.2 GHz, 8 cycles/byte	4 workers, overhead 300 µs	Storage verification

These are illustrative. Enter measured cycles/byte or measured throughput for your platform.

Formula Used

Software cycle model

t = overhead + (bytes × cycles/byte) ÷ (CPU Hz × workers)

Use when CRC runs on a CPU core. Cycles/byte depends on implementation, cache, memory bandwidth, and instruction set.

Hardware throughput model

t = overhead + bits ÷ (throughput × lanes)

Use when CRC is computed by a streaming engine. Throughput can be limited by DMA, bus width, or line rate.

How to Use

Enter your total data size and how many packets you process.
Select CRC width and the execution mode you use.
For software, provide CPU MHz, cycles/byte, and workers.
For hardware, provide throughput in Mb/s and lanes.
Set overhead to capture setup, DMA, or call costs.
Press Calculate to see time and effective throughput.

Professional Notes

Why CRC time matters in real systems

CRC adds integrity checks to storage, buses, and networks, but it still consumes compute and bandwidth. Estimating runtime helps engineers size buffers, select clock targets, and decide where acceleration is required. This calculator converts payload size and packetization into total bytes and bits, then applies a CPU cycle model or a streaming throughput model. The result is a time budget compared against deadlines, line rates, and interrupt windows.

Software cycle model and measurable inputs

For CPU execution, the key parameter is cycles per byte. Table-driven implementations often land in low‑teen cycles per byte on modern cores, while bitwise loops can be far slower. Pair that value with average CPU frequency and an effective worker count to reflect parallel lanes, threads, or cores. Add overhead to capture cache warmup, calls, DMA setup, and context switching, which can dominate small buffers.

Hardware throughput model for streaming engines

When CRC is produced by a peripheral or dedicated logic, throughput in megabits per second becomes the controlling term. The calculator treats throughput as a sustained rate and divides total bits across lanes. This matches designs such as Ethernet MAC CRC and DMA engines with inline checking. Use measured throughput from an I/O test, and keep overhead realistic for descriptor programming and interrupts.

Packetization, overhead, and latency tradeoffs

Splitting a payload into many packets changes average time per packet, even if total bytes stay constant. Higher packet counts can trigger more overhead events, raising latency and reducing effective throughput. For verification pipelines, long packets improve efficiency, but short packets may reduce buffering delay or improve fairness. This calculator reports total time, average packet time, and computed throughput for quick trade studies.

Interpreting results for capacity planning

Use the estimate to validate whether CRC fits inside a control loop, a storage scrub window, or a line‑rate target. If throughput is below your required data rate, reduce cycles per byte with optimized tables or SIMD, increase frequency, or raise workers. If hardware is selected, add lanes or widen the datapath. Re-run scenarios to document margins and justify choices. Record assumptions so future tests can reproduce the estimate.

FAQs

1) What does this calculator estimate?
It estimates processing time for CRC work over a given payload, either by CPU cycles per byte or by sustained hardware throughput, including a fixed overhead term.

2) How do I pick cycles per byte?
Use a microbenchmark on representative buffers. If you cannot measure, start with table-driven values around 8–16 cycles/byte and bitwise values much higher, then refine with profiling.

3) Why add overhead in microseconds?
Real pipelines include setup costs such as DMA programming, cache effects, interrupts, and function-call overhead. These costs can dominate short packets even when the CRC engine is fast.

4) What do workers and lanes represent?
Workers approximate parallel CPU execution, while lanes represent parallel hardware datapaths. Both scale compute capacity, but only if your workload is evenly divisible and not I/O bound.

5) Is the throughput output the same as link speed?
No. It is the effective CRC processing throughput implied by your inputs. Link speed may be higher or lower depending on framing, I/O waits, and other pipeline stages.

6) How accurate are the results?
Accuracy depends on how realistic your cycles/byte or throughput values are. Use measured numbers and include overhead; then validate by timing end-to-end CRC on real data paths.