Performance - 2.2 English

HBM/DDR4 Binary CAM Search LogiCORE IP Product Guide (PG336)

Document ID
PG336
Release Date
2021-08-12
Version
2.2 English

Maximum Frequencies

  • The HBM/DDR BCAM is designed to run at up to 325 MHz in UltraScale+™ -2 speed grade devices.
  • CORE_FREQUENCY = Max 325 MHz
  • LOOKUP_INTERFACE_FREQ = Max 300 MHz
  • AXI4_LITE_FREQUECY = Max 100 MHz

Latency

The maximum latency takes into account:
  • Refresh
  • Write Management Requests

Throughput

The lookup throughput corresponds to the LOOKUP_RATE parameter. The Management Request has strictly lower priority than the Lookup Request:

Guaranteed Management Request Rate = 20-LOOKUP_RATE/REPLICATION_FACTOR.

The HBM ECC scrubbing mechanism should be configured to have a minimal effect on throughput and latency. You are responsible for setting the ECC configuration in HBM. For details see the AXI High Bandwidth Controller LogiCORE IP Product Guide (PG276).

All read and write Management Requests are considered to use ENTRY_SIZE = 1024 bits for the purpose of throughput and latency calculations. For shorter entry sizes, the hardware and software API might in reality read and write less than 1024 bits.

Management operations are atomic operations. Complete entries are written to the CAM Database before they are made active (valid). The database is kept in a persistent state at all times in order for ongoing lookups to never fail.

A write Management Request writing an entry of ENTRY_SIZE = 1024 bits requires 34 write operations, 32 bits wide on the AXI4-Lite bus. The AXI4-Lite interface is a standard type. Refer to AXI4-Lite IPIF LogiCORE IP Product Guide (PG155).

The HBM/DDR BCAM uses Cuckoo hashing. This means that entries might move around in order to make room for a newly inserted entry. Every key insert generates 1.5 Management Requests in average, due to entry movement. Key updates and deletes generate one Management Request each.

For example, a system which supports 1M inserts + 1M deletes per second needs to support 1.5 * 1M + 1M = 2.5M Management Requests/s. Each Management Request requires 34 AXI-Lite operations which translates to a total of 2.5 * 34 =85M Management Requests/s.