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RC Bandwidth System

All about the RC bandwidth system, the complete rewrite of the bandwidth system.

See also RC Bandwidth Parameters


The RC bandwidth system is a complete rewrite of the bandwidth system. Its goals include:


HF20: Initial implementation.

Resource credits

Each account has a manabar called “resource credits.” Resource credits have the following characteristics:


How many RC’s are required for a transaction? Statelessly compute, for each transaction, how many of each resource it takes. Resources include:

Then each resource has an exchange rate. If CPU cycles cost 5 RC / megacycle, state memory costs 8 RC / byte, and history size costs 4 RC / byte, a transaction which takes 2 megacycles, creates 50 bytes of state, and has a 150 byte transaction size will cost 2*5 + 50*8 + 150*4 = 1010 RC.

Resource budget pools

A resource budget pool for each resource type will be established. The resource budget pool will have a per-block linear increase, a per-block percentage decrease, and a per-transaction decrease.

For example:

We can compute the new values as follows:

// when transaction is processed
bp.megacycles -= 2;
bp.state_bytes -= 50;
bp.history_bytes -= 150;

// per block additive
bp.megacycles += 2500;
bp.state_bytes += 5000;
bp.history_bytes += 25000;

// per block multiplicative
// of course this would be implemented as integer arithmetic
bp.megacycles *= 0.9998;
bp.state_bytes *= 0.9998;
bp.history_bytes *= 0.9998;

Resource pricing

The resource budget pool can be viewed as the blockchain’s “stockpile” of each resource, which it “sells” for RC. The price of each resource is based on the current level of the stockpile. Exactly how the price is determined isn’t very important, as long as it is a decreasing, smooth curve.

The specific cost curve is:

p(x) = A / (B + x)

where A and B are parameters which may be set to different values for different resources.