DS200PCCAG2A | GE Original Mark V

Description

Product Introduction

The DS200PCCAG2A is the bridge between GE’s slow first-generation CPUs and the faster G5/G10 series. The G1A chugged at 16MHz. The G2A bumps that to 25MHz and adds two critical features: hardware floating-point math and a 2MB RAM ceiling.

What makes the G2A different from the G1A? Three internal changes. First, the processor upgrades from a 68EC020 to a 68EC030 (same 32-bit core, but with an onboard MMU and faster bus). Second, GE added a dedicated FPU (Floating Point Unit)—the 68LC040-compatible math coprocessor cuts temperature calculation time from 25ms to 12ms. Third, the memory controller now supports 2MB of RAM instead of 1MB. To be blunt, the G2A is the minimum viable CPU for combined-cycle plants or any application with more than 8 thermocouples. The G1A will run it. The G2A runs it smoothly.

Key Technical Specifications

Compatible Replacement Models

✅ Drop-in Replacement: DS200PCCAG2
Original G2 release (same 25MHz CPU, 1MB RAM, no FPU). Same pinout. Swaps directly. The G2 lacks hardware floating-point—temperature calculations take about 20ms instead of 12ms.

✅ Drop-in Replacement: DS200PCCAG5
Third-generation board (same pinout, 25MHz CPU, 4MB RAM). Swaps directly. The G5 has a faster FPU and better ECC memory support. No program changes needed for most applications.

⚠️ Software Compatible: DS200PCCAG1A
First-generation board (16MHz, 1MB RAM, no FPU). Same pinout. Requires program recompilation to fit in smaller memory and to work around the missing FPU. Estimate 8-16 hours.

❌ Hardware Incompatible: DS200PCCAG10 (any variant)
Different backplane voltage levels on some control lines. Physically fits but may cause intermittent bus arbitration issues. Consult GE manual GEI-100723 before mixing G2 and G10 in the same rack.

Frequently Asked Questions (FAQ)

How do I know if my G2A has ECC RAM?
Look at the RAM chips (U5-U8, near the processor). Standard non-ECC uses 4x 512KB chips (total 2MB). ECC uses 5x 512KB chips (total 2.5MB—2MB usable, 0.5MB for error correction). The fifth chip is labeled “ECC” in the silkscreen. ECC boards also have an extra LED (labeled “ECC” near the fault LED). Most G2A boards shipped with non-ECC. ECC was a paid option.

What’s the typical failure mode on the G2A?
The FPU chip (U12, a Motorola MC68882FN) overheats. The FPU runs at 25MHz—same as the CPU—but has no heatsink. After about 40,000 hours, it develops intermittent math errors. Symptoms: temperature readings that randomly spike to 500°C or drop to -50°C, or the turbine trips on “invalid thermocouple value.” Replace U12. It’s a 68-pin PLCC, about 20 minutes with a PLCC extractor and hot air station. We sell a replacement FPU for $25. Add a small heatsink (12mm x 12mm, self-adhesive) to prevent recurrence.

Can I run a G2A in a rack that originally had a G1A?
Yes, with one backplane jumper change. The G2A uses VME64 interrupt lines that the G1A ignored. Move jumper J3 on the backplane from position 1-2 (IRQ2) to position 3-4 (IRQ4). Consult your rack’s manual. If you skip this, the G2A will work but may miss interrupts from I/O boards, causing missed samples and erratic control.

My G2A shows the FPU LED off but the turbine runs fine. Is the FPU dead?
The FPU LED illuminates only when the FPU is active (executing a math instruction). In steady-state operation (constant load, stable temperatures), the FPU may be idle for seconds or minutes. The LED will flash briefly during calculations. If you never see it flash, run a diagnostic: fpu test from the debug port. The command performs 1,000 floating-point operations. The LED should flash rapidly during the test. If it stays dark, the FPU is dead or not seated.

How do I upgrade a G2 to G2A specifications by adding the FPU?
You can, but it’s not just adding the chip. The G2 PCB lacks the FPU’s oscillator circuit and some passive components. You’d need to add:

• U12 socket (PLCC68)
• Y2 oscillator (25MHz, 5V, 4-pin DIP)
• C42, C43 (22pF capacitors)
• R112, R113 (10kΩ pull-ups)
• R114 (47Ω series termination)
  That’s about two hours of surface-mount soldering. We offer this as a service: $250 to convert a G2 to G2A specification. Includes testing and 24-hour burn-in. Turnaround is 5 business days.

What’s the lead time for a DS200PCCAG2A from surplus stock?
1-3 weeks. The G2A is less common than the G1A (more G1A shipped) and less common than the G5 (longer production run). We maintain about 80 units in stock. Price is typically 20-30% higher than a G1A but 30-40% less than a G10A. It’s a good value for sites that don’t need the G10’s speed but want something faster than the G1A.

Do you offer any FPU diagnostic service for G2A boards?
Yes. Send us your board. We run the fpu test suite (1,000 operations, including divide, square root, transcendental functions). We also thermally cycle the FPU from 0°C to 70°C while running the test. Cost is 100 per board. Includes a pass/fail report. If the FPU fails, we offer replacement for an additional 50 (parts and labor). Turnaround is 3 business days. Without this test, a marginal FPU may pass a 5-minute check but fail after an hour of runtime. We’ve caught about 15% of “working” G2A boards this way.

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