Description
Key Technical Specifications
- Microprocessor: 64 MHz 80486DX2
- User Memory: 1 Mbyte Battery-Supported CMOS RAM (512 Kbytes available for ladder logic)
- Firmware Storage: Flash Memory (Upgradable via PC serial connection)
- I/O Capacity: Up to 12K Discrete I/O, 8K Analog I/O (Simplex mode)
- Voting I/O: 2048 Voted Discrete Inputs/Outputs, 1024 Voted Analog Inputs
- Floating Point: Hardware-supported floating-point calculations
- Backplane Format: VME C.1 Standard
- Programming Software: MS-DOS or Windows (Windows 95/NT)
- Communication Ports: Ethernet TCP/IP, SNP Port (RS-485)
- Cooling Requirement: Forced Air (Requires 70 CFM fan in Slot 1 below CPU)
- Status Indicators: Four Green LEDs for CPU state
- Special Requirement: Must be paired with an independent C-program for Triple Modular Redundancy (TMR) to operate
Product Introduction
You don’t buy this CPU for a conveyor belt. The GE IC697CPM790 is a single-slot powerhouse built for the absolute worst-case scenarios: Emergency Shut-Down (ESD), fire and gas detection, and critical turbine controls. It runs on a 64 MHz 80486DX2 processor with hardware floating-point math, meaning it can chew through complex analog calculations without breaking a sweat. It’s got 1 Mbyte of battery-backed RAM and communicates over a VME C.1 backplane. Honestly, it’s a dinosaur by modern PC standards, but in a control cabinet, “dinosaur” just means “proven.”
Bottom line—this module is a beast, but it demands respect. The GE IC697CPM790 isn’t a plug-and-play toy. It requires a mandatory independent C-program to enable its Triple Modular Redundancy (TMR) and auto-test routines. Without that program loaded, it won’t even run. It also requires forced air cooling—a 70 CFM fan mounted directly below it—because a 64 MHz 486 gets hot in a sealed rack. The real value here is the TMR architecture. When two out of three processors agree, you get a safety integrity level that keeps multi-million dollar assets from turning into scrap metal.
Troubleshooting Quick Reference
- CPU Won’t Run (No Green LEDs): 90% chance the mandatory TMR C-program is missing or corrupted. This CPU literally refuses to execute ladder logic without it. Verify the program is loaded and matches the firmware revision.
- Overtemp Fault / CPU Resets: 80% chance the cooling fan is dead or clogged. This module requires a 70 CFM fan in the slot directly below it. Check the fan filter, verify airflow, and measure fan voltage. If the fan is running but the CPU still overheats, the thermal paste between the CPU and heatsink may have dried out.
- Battery Low LED / Memory Loss: 70% chance the onboard lithium battery is dead. The GE IC697CPM790 uses a battery to maintain the calendar clock and CMOS RAM. Replace the battery immediately and reload the program from a backup. If memory still corrupts, the CMOS RAM chip is failing.
- Comm Failure (Ethernet/SNP): 60% likely a termination or cabling issue. For RS-485 SNP, verify the 120-ohm termination resistors are in place at both ends of the daisy chain. For Ethernet, check the link LED and verify the TCP/IP settings haven’t been overwritten.
Application Scenarios & Pain Points
- Gas Turbine Overspeed Protection: The GE IC697CPM790 was the gold standard for turbine control in the 90s and 2000s. The pain point is that these turbines are still running, but the OEM has moved on to newer platforms. Finding a tested CPU with the exact TMR C-program version is a nightmare.
- Offshore ESD Systems: Exposed to salt spray, vibration, and extreme temps. The GE IC697CPM790 was designed for this environment. Now, platforms are aging, and maintenance teams are paying $3,000+ for new surplus because a failed ESD CPU means shutting down production until a replacement arrives.
- Petrochemical Fire & Gas Detection: Safety-critical monitoring loops. The challenge is firmware compatibility. The GE IC697CPM790 firmware is stored in flash and can be upgraded, but mixing firmware revisions across redundant CPUs can cause voting failures. Plants are stuck maintaining systems with documentation that hasn’t been updated in 15 years.
GE IC697CPM790
Compatible Replacement Models
- ✅ Drop-in Replacement: (exact match). No hardware changes needed. Copy the Run/Stop switch position, memory protection key, and verify the TMR C-program matches. Cost: 3,000–6,000. Verify the PCB revision and firmware version match your existing redundant pair.
- ⚠️ Software Compatible: IC697CPM790RR (if available). Same processor and memory, but may require a firmware update or TMR C-program recompile. Budget 8-16 hours of engineering time. Confirm the VME backplane slot configuration matches before ordering.
- ❌ Hardware Incompatible: GE PACSystems RX7i (IC698CPE0xx) or PACSystems RX3i. Different backplane (PCI vs. VME), different rack, different programming software (Proficy Machine Edition vs. LogicMaster 90). This is a multi-year, multi-million dollar migration project requiring full SIL re-validation. Do NOT attempt as a field replacement.
