AES-GCM-256 Specifics and Memory Partitioning - AES-GCM-256 Specifics and Memory Partitioning - 1.0 English

AES-GCM-256 Specifics and Memory Partitioning - AES-GCM-256 Specifics and Memory Partitioning - 1.0 English - PG456

Integrated DDR5/LPDDR5/5X Memory Controller LogiCORE IP Product Guide (PG456)

Document_ID

PG456

Release_Date

2026-08-07

Version

1.0 English

AES-GCM authentication metadata (message authentication codes and initialization vectors) is stored in DRAM by default, consuming 1/4 of the GCM protected data size. ACE calculates and displays partition values automatically. Refer to the following table.

Table 1. ACE Calculations
ACE Field	Formula / Description	Example (4 GB = 4096 MB)
Metadata Size (in DRAM)	Single-Level Authentication: Reserved GCM Data Size / 4 Dual-Level Authentication: Reserved GCM Data Size / 8	Single-Level: 512 MB
Maximum GCM data size	Single-Level Authentication: Total Memory Size (M) - Metadata - Rounding ≈ 4M/5 Dual-Level Authentication: 64 MB	≈3276 MB
Reserved GCM Data Size	User-set, must be ≤ Maximum GCM data size. Set before adding GCM region destinations.	Example, 2048 MB
Metadata ILC Size (ECC+GCM)	Metadata Size / 8 (when Inline ECC + GCM both active)	64 MB
Available memory (GCM only)	M − Metadata	≈3584 MB
Available memory (GCM + ILECC)	M − Metadata − Metadata ILC − ECC Storage	≈3520 MB

Important: Set the Reserved GCM Data Size field in ACE before defining GCM region destinations. This reserves DRAM space for GCM data and prevents ACE from allowing over-allocation. Set to a value no greater than the Maximum GCM data size displayed by ACE.