A20B-3300-0295 | FANUC i-Series Model B Intel 486DX CPU Card — 16MB Integrated DRAM / Series 15i / 16i / Robot Systems
Processor and Memory on One Card
The A20B-3300-0295 combines an Intel 486DX processor with 16MB of DRAM on a single plug-in card. Both elements are present on the same PCB — no separate DRAM expansion module is required. This integrated design provides the full CPU and working memory needed for the FANUC i-series Model B control system in a single replaceable unit.
For maintenance, a single spare card addresses both CPU and DRAM failure modes. If the system develops a processing fault, a DRAM fault, or a fault that cannot be isolated to one specific element, fitting an A20B-3300-0295 resolves the issue whether the root cause was in the processor or the memory.
Key Specifications
| Parameter |
Value |
| Processor |
Intel 486DX |
| DRAM |
16MB integrated |
| Compatible |
FANUC 15i, 16i, robot i-series |
| Generation |
i-series, Model B |
| Form Factor |
Plug-in CPU module |
| Series |
A20B-3300 |
Series 15i and 16i — Demanding Different Things From the Same Hardware
The A20B-3300-0295 serves FANUC's 15i and 16i CNC product lines — machines with substantially different capability profiles but sharing the same Model B hardware generation.
The Series 15i is FANUC's high-performance CNC, deployed on complex multi-axis machines — 5-axis machining centres, compound turning centres, and machines requiring aggressive PMC programme complexity and extensive look-ahead capability. The 16MB working memory supports the larger runtime footprint of 15i-configured systems.
The Series 16i is the workhorse of FANUC's i-generation CNC range — widely deployed on machining centres, turning centres, and general-purpose machine tools. It has one of the largest installed bases of any FANUC CNC generation, which means replacement CPU cards like the A20B-3300-0295 are a commonly needed maintenance item.
Both systems use the same A20B-3300-0295 because they share the same Model B motherboard hardware. The FANUC system software in the FROM modules determines which CNC type the system operates as.
Application Scenarios
Series 15i 5-axis machining centre: The CNC fails to complete its boot sequence, displaying system alarm codes. After confirming FROM and SRAM modules are intact, the A20B-3300-0295 CPU card is replaced. The 15i resumes normal operation with all previously stored data intact.
Series 16i preventive maintenance: A high-volume production machining centre operating on two shifts undergoes a planned CNC card refresh after an extended service period. The A20B-3300-0295 is replaced alongside other aged electronic components to reset the card's service life before an age-related failure can cause unplanned downtime.
FAQ
Q1: How does A20B-3300-0295 differ from A20B-3300-0291?
Both are Intel 486DX CPU modules with 16MB integrated DRAM for FANUC i-series Model B hardware. The difference is a hardware revision within the same functional specification — component selection or PCB layout changes that FANUC applies during the production life of the card. Both deliver the same 486DX processing and 16MB DRAM, and either correctly replaces the other in an i-series Model B system.
Q2: Is CNC data preserved after replacing the A20B-3300-0295?
CNC programmes, parameters, and tool data reside in FROM and SRAM modules — not on the CPU card. Replacing the A20B-3300-0295 does not affect stored data, provided the FROM and SRAM modules remain installed and the SRAM battery is charged. The CNC reloads its software from FROM and reads its parameter data from SRAM on the next power-up. Always maintain a current backup as standard maintenance practice.
Q3: What failure symptoms distinguish a CPU card fault from a FROM or SRAM fault?
FROM module faults: alarms specifically about system software loading failure; the CNC halts at a specific initialisation step related to reading software. SRAM faults: alarms about parameter or programme data errors; data that was previously correct now appears corrupted. CPU card faults: more fundamental failures — the system does not initialise correctly, exhibits erratic programme execution across multiple tasks simultaneously, or fails in a way that changes behaviour unpredictably. FROM and SRAM faults tend to be consistent and reproducible; CPU faults often are not.
Q4: Can the A20B-3300-0295 be used in a Series 21i-B (Model B) system?
The A20B-3300 series CPU cards are tied to specific CNC model families within the Model B generation. While the 21i-B uses Model B hardware, its main board may differ from the 15i/16i main board in CPU card interface specifications. Confirm compatibility from the 21i-B hardware documentation before fitting the A20B-3300-0295 in a 21i application.
Q5: What determines how much DRAM is needed for the CNC application?
DRAM capacity requirements are set by the CNC system software, the number of active options, the size of the programme look-ahead buffer allocation, and the PMC programme's data register requirements. For the Series 15i and 16i Model B generation, 16MB is the standard specification — the CNC software is designed around this allocation. Higher-capacity cards would not be beneficial because the CNC software does not address additional memory beyond its designed allocation.
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