A20B-3300-0475 Fanuc PCB Board A20B33000475 A2OB-33OO-O475

A20B-3300-0475 | FANUC A3 CPU Module — 128MB Integrated DRAM / High-Capacity CNC Processor Card / A20B-3300 Series

128MB DRAM — A Significant Generational Step

Tracking DRAM capacity across the A20B-3300 CPU module series shows the evolution of FANUC CNC processing capability. Earlier generations carried 8MB, then 16MB, then 32MB of DRAM. The A20B-3300-0475 brings 128MB of integrated DRAM — a substantial step that reflects the demands of more recent FANUC CNC platforms.

Working memory at 128MB enables:

Larger programme look-ahead buffers: The CNC can buffer more G-code blocks ahead of the cutting point, enabling smooth execution at high feedrates even with complex, dense tool path programmes.

More sophisticated PMC programmes: Advanced machine sequence logic, multi-device communication management, and complex conditional processing place higher demands on the CPU's working memory environment.

Enhanced operating system and option software: Each generation of FANUC CNC software grows as more features are integrated. 128MB working memory accommodates the full-featured software image of the CNC platform without compromise.

Key Specifications

Integrated DRAM — One Board, Complete Function

The A20B-3300-0475 integrates all 128MB of DRAM directly onto the CPU card PCB. There is no separate DRAM expansion module required. The full working memory allocation is delivered in a single part number.

This integration simplifies system service. When a CPU card or working memory issue is suspected, the A20B-3300-0475 replacement addresses both in one operation. A single board in stock covers both CPU and DRAM failure modes, reducing the range of spares needed.

Application Scenarios

CNC boot failure with A3 main board: A FANUC CNC system with an A3 main board configuration fails to complete its start-up sequence. Memory-related alarm codes appear. The A20B-3300-0475 CPU card is replaced as the combined CPU and DRAM module. The CNC resumes normal operation after fitting the replacement.

Spare card for high-value production equipment: A machining centre running a FANUC CNC platform with 128MB DRAM CPU requirements maintains an A20B-3300-0475 as a critical spare. The card is available immediately on CPU module failure — reducing repair-to-production time from days to hours.

FAQ

Q1: How does A20B-3300-0475 differ from A20B-3300-0471 (also 128MB DRAM)?

Both are 128MB DRAM CPU modules, but they carry different board type designations: the -0475 is the A3 type; the -0471 is the i-B3 type for 15i/16i/18i/21i Model B systems. These different designations indicate different physical connector interfaces matched to different main board generations. They are not interchangeable — always match the CPU card type to the main board designation of the specific CNC system.

Q2: Does the A20B-3300-0475 include any CNC system software?

No. CNC system software is stored in FROM (Flash ROM) modules — separate plug-in boards in the FANUC control system. The A20B-3300-0475 provides the processing core and 128MB working memory only. On power-up, the CNC reloads its software from the FROM modules into the CPU card's DRAM. Replacing the CPU card does not affect the FROM content or the SRAM-stored parameters.

Q3: Can the A20B-3300-0475 be used to upgrade a system previously running a lower DRAM capacity CPU card?

This depends on whether the main board's CPU card slot is rated for the A3 board type and whether the CNC software version supports 128MB working memory. Using a higher-capacity card in a system that previously ran with less DRAM is not harmful if the physical compatibility is confirmed. However, the system software must be able to address the full 128MB — verify from the CNC's hardware and software documentation before fitting as an upgrade rather than a like-for-like replacement.

Q4: What is the correct procedure after fitting the A20B-3300-0475?

After installing the CPU card, power up the CNC and observe the boot sequence. The system should complete initialisation, load its software from FROM, and read its parameters from SRAM. Verify that all axes, PMC functions, and communication options operate correctly. If FROM content or SRAM parameters are missing, restore from backup. Document the replacement in the machine's maintenance record.

Q5: Are there other A3 CPU module variants besides A20B-3300-0475 in the A20B-3300 series?

Yes. Within the A20B-3300 series, multiple CPU modules carry the A3 type designation at different DRAM capacities. The -0475 is the 128MB variant. Other A3 variants may carry different DRAM sizes. Always confirm both the board type (A3) and DRAM capacity from the installed module's label before ordering — matching both ensures the replacement meets the full specification of the original module.