1. Official standard specifications (Motorola/Emerson)

CPU: MC68040 32MHz (built-in FPU, MMU, 8KB unified cache)

Form: 6U dual-height (2 slots) VME SBC

DRAM: 8MB (non-parity)

SRAM: 512KB, battery backup (NVRAM)

Flash: 1MB (board-level firmware / monitoring)

I/O (standard):

Ethernet: 10BASE-T (RJ45) + 10BASE2 (BNC), DMA

SCSI-2 (50pin narrowband, standard + DMA)

Serial port: 2×RS-232/422/485 (software selectable)

Parallel port: 1×Centronics

RTC: Battery-backed real-time clock

Expansion: 4×IP slots, no PMC slots (key difference from 521A)

VME: A16/A24/A32, D8/D16/D32, master / slave / system controller

Temperature:

522 (standard version): 0℃~+70℃

522A (wide temperature version): –40℃~+85℃ (market mainstream)

II. 522 vs 520A vs 513A vs 521A (Core Differences) Table

Model CPU DRAM PMC SCSI Position

520A 32MHz 8MB ❌ ❌ Basic High-End (no SCSI/PMC)

513A 32MHz 8MB ❌ ✅ With SCSI, no PMC (Old model)

522/522A 32MHz 8MB ❌ ✅ With SCSI, no PMC (New main model)

521A 32MHz 8MB ✅ ✅ All-round Top-End (with PMC + SCSI)

Conclusion: 522/522A = 521A - PMC slot = 513A upgraded version (better process / stability).

To have SCSI, no PMC → Choose 522A (Most recommended)

No SCSI, no PMC → Choose 520A

To have SCSI + PMC → Choose 521A

III. Application scenarios (522/522A is the most suitable)

✅ Replace the old model 513/513A: Direct compatibility, better performance, more reliable wide temperature

✅ Need SCSI-2 storage (hard disk / tape drive), no need for PMC high-speed expansion

✅ Industrial control, data acquisition, rail transit, military industry: Wide temperature, high shock resistance, stable long-term supply

✅ Medium budget, need 8MB + dual high + FPU + SCSI + basic network port serial port

IV. Replacement relationship (fully compatible)

Directly replace 513A: Function is the same, updated process, stronger stability

Replace 520A: Add SCSI interface, suitable for storage needs

Upgrade to 521A: Add PMC slot, support high-speed expansion such as fiber / gigabit network card

Upgrade to 532A: Memory expanded to 16MB, other are consistent