ND-5000 (SAMSON) Architecture Differences¶

How SINTRAN III Handles ND-5000 vs Standard ND-500 Systems

Overview¶

This document analyzes how SINTRAN III distinguishes between standard ND-500 systems (using DMA interface PCB 3022) and ND-5000 "SAMSON" systems (using Octobus/Multi Function Bus architecture).

Important Note: The ND-5000 maintains software compatibility with ND-500 - it runs the same instruction set, uses the same registers, and executes the same programs. The differences documented here are in the hardware interface between the ND-100 (I/O processor) and the main CPU.

1. CPU Generations¶

The ND-500 CPU software architecture had three physical implementations:

Generation	Implementation	Systems	Interface
1st	ND-500/1	ND-520, ND-540, ND-560	DMA (PCB 3022)
2nd	ND-500/2	ND-510, ND-530, ND-550, ND-560, ND-570, ND-580	DMA (PCB 3022)
3rd	ND-5000 (SAMSON)	ND-5X00 series	Octobus + MFB

Source: ND-05.009.4 EN ND-500 Reference Manual, pages 17-18

All three implementations run the same instruction set, same registers, and same addressing modes. The difference is purely in hardware implementation and the interface to the I/O processor (ND-100/ND-110).

2. Hardware Interface Differences¶

Standard ND-500 (DMA Interface - PCB 3022)¶

┌──────────┐                  ┌──────────┐
│  ND-100  │    PCB 3022      │  ND-500  │
│   I/O    │◄────────────────►│   CPU    │
│Processor │   DMA Interface  │ ND-500/1 │
└────┬─────┘                  │ ND-500/2 │
     │                        └────┬─────┘
     │                             │
     │      ┌──────────┐           │
     └─────►│   5MPM   │◄──────────┘
            │ Multiport│
            │  Memory  │
            └──────────┘

Characteristics: - IOX commands via PCB 3022 device registers - Status read via RSTA5 register (IOX operation) - 5ILOCK bit indicates CPU running - 5POWOF bit indicates power failure

ND-5000 (SAMSON - Octobus + MFB)¶

┌──────────┐                  ┌──────────┐
│ ND-100/  │    Octobus       │  ND-5000 │
│  ND-110  │◄────────────────►│ (SAMSON) │
│   I/O    │  Multi Function  │   CPU    │
│Processor │      Bus         │          │
└────┬─────┘                  └────┬─────┘
     │                             │
     │      ┌──────────┐           │
     └─────►│   MFB    │◄──────────┘
            │  Shared  │
            │  Memory  │
            └──────────┘

Characteristics: - Communication via Octobus protocol - Status via MAILINK (mailbox link) in shared memory - Multi Function Bus (MFB) for direct memory access - Up to 32 MB physical memory - Private memory regions possible

3. SAMSON Detection and Initialization¶

Boot-Time Detection¶

During SINTRAN cold start, the system checks for Octobus presence:

Source: PH-P2-OPPSTART.NPL lines 3921-3929

1CH5CPU:     *TRA IIC                                % Read octobus if. status
             A:=200; *TRR IIE
             T:=100406; *IOXT; TRA IIC
             IF A=0 THEN                             % Octobus present? - (assumes Samson)
                DO                                   % Wait for data ready
                   *IOXT
                WHILE A NBIT 3
                OD
                ASTATION\/COMD=:5STATION

Detection Logic: 1. Read Octobus interface status via IOX (device 100406 octal) 2. If A=0, Octobus is present (assumes SAMSON) 3. Wait for data ready (bit 3) 4. Store station number in 5STATION

CPU Counting and Registration¶

Source: RP-P2-N500.NPL lines 973-980

X:="S5CPUDF"; 0=:NSAMSON=:N5CPU
DO WHILE X<<="E5CPUDF"
   IF X.CPUAVAILABLE/\5CPUTYPE=SAMSON THEN
      X.CPUNO+FN5DEST-1=:X.5STATION
      *IOF
      A:=X;        *IRW LV12B DB
      "LMDF";      *IRW LV12B DX
      "CON5IDENT"; *IRW LV12B DP

What This Does: 1. Initialize NSAMSON (SAMSON count) and N5CPU (total ND-500 count) to 0 2. Loop through CPU datafields (S5CPUDF to E5CPUDF) 3. For each SAMSON CPU: - Calculate Octobus station number: CPUNO + FN5DEST - 1 - Store in 5STATION field - Disable interrupts (*IOF) - Set up level 12 interrupt (*IRW LV12B) with: - DB = CPU datafield address - DX = LMDF (local message data field) - DP = CON5IDENT (connection identification)

4. Status Checking Differences¶

The most significant operational difference is how SINTRAN checks if an ND-500/ND-5000 CPU is active.

500HA Subroutine¶

Source: MP-P2-N500.NPL lines 264-269

% Local subroutine to test if nd-500 active
500HA: IF B<<"S5CPUDF" OR B>>"E5CPUDF" THEN EXIT FI
       IF CPUAVAILABLE/\5CPUTYPE><SAMSON THEN    % DMA interface?
          T:=HDEV+RSTA5; *IOXT
          IF A NBIT 5ILOCK OR A BIT 5POWOF THEN EXIT FI
       FI
       EXITA

Interpretation¶

CPU Type	Check Method	Running If
ND-500 (DMA)	`IOX RSTA5` register	`5ILOCK` bit set AND `5POWOF` bit clear
ND-5000 (SAMSON)	Skip hardware check	Assume running (use MAILINK for actual status)

Key Point: For SAMSON, the 500HA subroutine does not perform hardware status check - it immediately returns via EXITA. The actual status is determined by checking MAILINK elsewhere.

MAILINK Status Checking¶

Source: RP-P2-N500.NPL lines 85-91

IF A/\5CPUTYPE=SAMSON THEN
   % Nd-500 samson on octobus line - test if memory layout ok : -
   IF MAILINK><-1  THEN
      A:=0; X:="S5CPUDF"
      DO WHILE X<<="E5CPUDF"; A\/X.C5STAT; X+5CPUDFSIZE; OD
      IF A/\C5PFMASK=0 GO NN5S1
   FI

Logic: - For SAMSON: Check if MAILINK is initialized (not -1) - If initialized: Check all CPU status fields for power fail mask - If no power fails detected: proceed to scheduling (NN5S1)

5. Communication Mechanisms¶

Standard ND-500: IOX Commands¶

Communication uses IOX instructions to PCB 3022 registers:

Register	Direction	Purpose
RSTA5	Read	Status (5ILOCK, 5POWOF bits)
WSTA5	Write	Commands
WDAT5	Write	Data out
RDAT5	Read	Data in

ND-5000 (SAMSON): Mailbox + Shared Memory¶

Communication via shared memory structures:

Mechanism	Purpose
`MAILINK`	Mailbox link (message queue pointer)
`MAIL1LINK`	Secondary mailbox link
`5STATION`	Octobus station number
MFB shared memory	Direct data access

Initialization of mailbox links:

Source: 5P-P2-MON60.NPL lines 560-564

X:="S5CPUDF"
DO WHILE X<<="E5CPUDF"
   A:=-1=:X.MAIL1LINK=:X.MAILINK
   X+5CPUDFSZ
OD

Both MAILINK and MAIL1LINK are initialized to -1 (invalid) at startup.

6. Execution Queue Differences¶

A significant scheduling difference exists for SAMSON systems.

Source: s3vs-4.symb line 57255 (also in performance sampling code)

IF CPUAVAILABLE/\5CPUTYP=SAMSON GO OUT % Only one exec. q.

Implication: SAMSON systems use only one execution queue while standard ND-500 systems may use multiple execution queues.

This affects process scheduling - SAMSON appears to have a simpler queue model.

7. Key Variables and Symbols¶

From DP-P2-VARIABLES.NPL¶

Variable	Type	Description	Source Line
`NSAMSON`	INTEGER	Number of SAMSON CPUs	112
`N5CPU`	INTEGER	Total number of ND-500/5000 CPUs	(nearby)
`5SWPROC`	INTEGER	Swapper process number	116

CPU Datafield Fields (per CPU)¶

Field	Purpose
`CPUAVAILABLE`	CPU availability flags
`5CPUTYPE`	CPU type (SAMSON or other)
`5STATION`	Octobus station number (SAMSON only)
`MAILINK`	Mailbox link for communication
`MAIL1LINK`	Secondary mailbox link
`CPUNO`	CPU number
`C5STAT`	CPU status flags
`HDEV`	Hardware device base address

Constants¶

Source: Verified from SINTRAN L07 symbol files (../NPL-SOURCE/SYMBOLS/L07/SYMBOL-1-LIST.SYMB.TXT)

Symbol	NPL (5-char)	Octal Value	Description
`SAMSON`	SAMSO	000003	CPU type constant for ND-5000
`OLD500`	OLD50	000001	CPU type constant for standard ND-500
`5CPUTYPE`	5CPUT	000007	CPU type field offset
`RSTA5`	RSTA5	000002	Read status register offset
`5ILOCK`	5ILOC	000005	Interface locked - bit 5 (mask 0x0020)
`5POWOF`	5POWO	000010	Power was off - bit 8 (mask 0x0100)
`5ALIVE`	5ALIV	000015	CPU is alive - bit 13 (mask 0x2000)

8. I/O Architecture¶

Current Implementation (from source code)¶

The I/O system remains on the ND-100/ND-110 "I/O processor" for both standard ND-500 and ND-5000:

Source: ND-05.009.4 EN ND-500 Reference Manual, page 18

THE I/O PROCESSOR: - Supervises the CPU - Runs the I/O system, file system, operating system and job scheduling - Runs local I/O-processor jobs

For both ND-500 and ND-5000, the I/O processor (ND-100/ND-110) handles: - Disk I/O (including SCSI) - Terminal I/O - Network I/O - All device drivers

Multi Function Bus (MFB) - ND-5000¶

The ND-5000 uses Multi Function Bus for memory:

Source: ND-05.009.4 EN ND-500 Reference Manual, page 19

MEMORY: - Multi Function Bus main memory with direct access for the ND-5000 CPU, the I/O processor CPU and DMA transfer devices - Physical main memory up to 32 Mbytes - Memory fully or partially shared between the I/O processor and ND-500 type CPU

Key Difference: MFB allows direct DMA access from I/O devices to shared memory, potentially bypassing the I/O processor for data transfer.

DOMINO I/O System (Future)¶

Source: ND-05.009.4 EN ND-500 Reference Manual, page 17

Until now the I/O processor has been an ND-100, but when the DOMINO I/O system is introduced, other types of I/O processors will be possible.

Source: ND Linker User Guide, page 3088

Use this command if you are programming for the PIOC or DOMINO.

Note: DOMINO uses Motorola MC680x0 processors, representing a move away from ND-100 as the I/O processor. This is not fully documented in available NPL sources.

Octobus Devices¶

Device numbers 2400-2477 (octal) are reserved for Octobus devices:

Device Range	Description
2400-2417	Octobus unit 0
2420-2437	Octobus unit 1
2440-2457	Octobus unit 2
2460-2477	Octobus unit 3

Source: Monitor Calls manual, Appendix I

9. Mermaid Diagrams¶

System Architecture Comparison¶

flowchart TB
    subgraph ND500["Standard ND-500 System"]
        A1[ND-100 I/O Processor]
        B1[PCB 3022 DMA Interface]
        C1[ND-500/1 or ND-500/2 CPU]
        D1[5MPM Multiport Memory]

        A1 <-->|IOX Commands| B1
        B1 <-->|DMA| C1
        A1 <-->|Memory Access| D1
        C1 <-->|Memory Access| D1
    end

    subgraph ND5000["ND-5000 (SAMSON) System"]
        A2[ND-100/ND-110 I/O Processor]
        B2[Octobus Interface]
        C2[ND-5000 CPU]
        D2[MFB Shared Memory]

        A2 <-->|Mailbox| B2
        B2 <-->|Octobus| C2
        A2 <-->|MFB Direct| D2
        C2 <-->|MFB Direct| D2
    end

    style A1 fill:#2196F3,stroke:#1976D2,stroke-width:2px,color:#fff
    style A2 fill:#2196F3,stroke:#1976D2,stroke-width:2px,color:#fff
    style B1 fill:#9C27B0,stroke:#7B1FA2,stroke-width:2px,color:#fff
    style B2 fill:#9C27B0,stroke:#7B1FA2,stroke-width:2px,color:#fff
    style C1 fill:#4CAF50,stroke:#388E3C,stroke-width:2px,color:#fff
    style C2 fill:#4CAF50,stroke:#388E3C,stroke-width:2px,color:#fff
    style D1 fill:#FFA726,stroke:#F57C00,stroke-width:2px,color:#fff
    style D2 fill:#FFA726,stroke:#F57C00,stroke-width:2px,color:#fff

Status Check Decision Flow¶

flowchart TD
    A[500HA: Check CPU Status] --> B{CPU in valid range?}
    B -->|No| EXIT1[EXIT - Out of Range]
    B -->|Yes| C{5CPUTYPE = SAMSON?}

    C -->|No - Standard ND-500| D[IOX: Read RSTA5]
    D --> E{5ILOCK bit set?}
    E -->|No| EXIT2[EXIT - Not Running]
    E -->|Yes| F{5POWOF bit set?}
    F -->|Yes| EXIT3[EXIT - Power Off]
    F -->|No| EXITA[EXITA - CPU Running]

    C -->|Yes - ND-5000| EXITA

    style A fill:#2196F3,stroke:#1976D2,stroke-width:2px,color:#fff
    style D fill:#E91E63,stroke:#C2185B,stroke-width:2px,color:#fff
    style EXITA fill:#4CAF50,stroke:#388E3C,stroke-width:2px,color:#fff
    style EXIT1 fill:#F44336,stroke:#D32F2F,stroke-width:2px,color:#fff
    style EXIT2 fill:#F44336,stroke:#D32F2F,stroke-width:2px,color:#fff
    style EXIT3 fill:#FFA726,stroke:#F57C00,stroke-width:2px,color:#fff

SAMSON Initialization Sequence¶

sequenceDiagram
    participant BOOT as Boot Code
    participant CPUDF as CPU Datafield
    participant OCT as Octobus
    participant SAM as SAMSON CPU

    BOOT->>BOOT: Initialize NSAMSON = 0, N5CPU = 0

    loop For each CPU datafield
        BOOT->>CPUDF: Check 5CPUTYPE
        alt Is SAMSON
            BOOT->>CPUDF: Calculate 5STATION = CPUNO + FN5DEST - 1
            BOOT->>BOOT: Disable interrupts (*IOF)
            BOOT->>OCT: Set up Level 12 interrupt handler
            Note over OCT: DB = CPU datafield<br/>DX = LMDF<br/>DP = CON5IDENT
            BOOT->>SAM: Initialize via Octobus
        else Is Standard ND-500
            BOOT->>CPUDF: Use DMA interface setup
        end
    end

10. Verification and Assumptions¶

Verified from Source Code¶

Finding	Source File	Line(s)	Confidence
`NSAMSON` variable for counting SAMSON CPUs	DP-P2-VARIABLES.NPL	112	HIGH
`5CPUTYPE=SAMSON` check for CPU type	MP-P2-N500.NPL	265	HIGH
500HA skips IOX for SAMSON	MP-P2-N500.NPL	265-269	HIGH
`MAILINK` used for SAMSON communication	5P-P2-MON60.NPL	562, 702	HIGH
SAMSON has single execution queue	s3vs-4.symb	57255	HIGH
`5STATION` stores Octobus station	RP-P2-N500.NPL	976	HIGH
Mailbox links initialized to -1	5P-P2-MON60.NPL	562	HIGH
Octobus detection at boot	PH-P2-OPPSTART.NPL	3921-3929	HIGH
XRS5CPU called for SAMSON restart	MP-P2-N500.NPL	3358-3359	HIGH
XTER500 called for non-SAMSON	MP-P2-N500.NPL	3361	HIGH

Verified from Reference Manuals¶

Finding	Source	Confidence
ND-5000 is 3rd generation ND-500 implementation	ND-05.009.4 page 17	HIGH
Multi Function Bus (MFB) used for ND-5000 memory	ND-05.009.4 page 19	HIGH
Up to 32 MB physical memory supported	ND-05.009.4 page 19	HIGH
DOMINO I/O system planned for future	ND-05.009.4 page 17	HIGH
Same instruction set for all ND-500 variants	ND-05.009.4 page 18	HIGH
Octobus devices at 2400-2477 octal	Monitor Calls Appendix I	HIGH

Interpretations (Low Uncertainty)¶

Interpretation	Evidence	Uncertainty
SAMSON uses Octobus for CPU communication instead of DMA	Code explicitly checks `5CPUTYPE=SAMSON` vs IOX operations	LOW
MAILINK replaces hardware status polling for SAMSON	500HA skips IOX for SAMSON, other code checks MAILINK	LOW
ND-5000 I/O still handled by ND-100 I/O processor	No code shows ND-5000 direct I/O handling	LOW

Assumptions (Higher Uncertainty)¶

Assumption	Why Assumed	Uncertainty
SCSI controllers on ND-5000 still managed by ND-100	No SAMSON-specific SCSI code found; manual states I/O processor handles I/O	MEDIUM
"Own bus and I/O controllers" refers to MFB direct DMA capability	MFB allows direct access from DMA devices, but driver code not found	MEDIUM
DOMINO system would replace ND-100 for I/O	Mentioned in manual but no implementation in available sources	MEDIUM
Single execution queue for SAMSON is architectural requirement	Comment says "Only one exec. q." but reason not documented	MEDIUM

What This Document Does NOT Cover¶

Detailed Octobus protocol - Low-level Octobus communication not documented in NPL sources
DOMINO I/O system - Future system mentioned but not implemented in available code
MFB hardware details - Requires ND-05.020 (ND-5000 Hardware Description) manual
SAMSON microcode differences - Hardware implementation details

References¶

NPL Source Files¶

File	Content
`MP-P2-N500.NPL`	ND-500/5000 monitor program, 500HA subroutine
`RP-P2-N500.NPL`	Runtime program, SAMSON initialization
`PH-P2-OPPSTART.NPL`	Boot code, Octobus detection
`5P-P2-MON60.NPL`	Monitor calls, mailbox initialization
`DP-P2-VARIABLES.NPL`	Variable definitions including NSAMSON
`MP-P2-PERF-SAMP.NPL`	Performance sampling code

Official Manuals¶

Manual Number	Title
ND-05.009.4	ND-500 Reference Manual
ND-05.015	ND-500/2 Hardware Description
ND-05.020	ND-5000 Hardware Description (referenced, not available)
ND-860228-2	SINTRAN III Monitor Calls
ND-860289-2	ND Linker User Guide

Version History¶

Date	Version	Changes
2026-01-29	1.0	Initial document - SAMSON/ND-5000 architecture analysis

Parent: README.md - ND-500 Documentation Related: ND500-IF-USAGE-DEEP-ANALYSIS.md - IOX interface analysis Related: ND500-SWAPPER-LOADING-MECHANISM.md - Swapper loading