DSP Slice Requirement Calculator
Work out dsp slice requirement instantly with clear inputs, formula shown and shareable results.
About DSP Slice Requirement Calculator
DSP slice count is the required multiply rate divided by what one slice delivers at the DSP clock. Because the DSP clock usually exceeds the sample rate, each slice can be time-shared across several taps — 400 MHz against 50 MSPS gives eight multiplies per slice per sample.
Formula
DSP slices
slices = ceil(multiplies per sample x sample rate / DSP clock)
Worked example
With the default values below, DSP Slice Requirement Calculator returns DSP slices required of 16. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Multiplies per sample
- 128 multiplies
- Sample rate
- 50 MSPS
- DSP clock
- 400 MHz
- Multiplier width needed
- 25 bits
Results
- DSP slices required
- 16 slices
- Multiply rate
- 6.40 GMAC/s
- Multiplies per slice per sample
- 8.00 x
- Slices per multiply for this width
- 1 slices
Step by step
- 1Values used
- 2DSP slices
- 3DSP slices required= 16 slices
- 4Multiply rate= 6.40 GMAC/s
- 5Multiplies per slice per sample= 8.00 x
- 6Slices per multiply for this width= 1 slices
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
What is time-sharing in an FIR filter?
Running the multiplier faster than the sample rate so one physical DSP evaluates several taps per sample. It trades latency and control complexity for resource count.
When does a multiply need more than one slice?
When operand widths exceed the native size (typically 18x25 bits). Wider multiplies are decomposed into several slices plus adders.
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