Oric-1 & Oric Atmos Machine Hub
Tangerine 6502A workbench reference — Oric-1 (16K/48K) & Atmos architecture, 7905 negative-ground PSU quirk, HCS10017 ULA & DRAM diagnostics, active RGB SCART buffer schematic, and 34-pin expansion pinouts.
+9V DC Centre-Positive PSU & Why the Oric Uses a 7905 Negative Regulator!
Don't be fooled when you open an Oric-1 or Oric Atmos and see a 7905 (−5 V negative voltage regulator, `IC23`) bolted to the heatsink! Instead of regulating the +9 V line with a 7805, Tangerine's engineers tied the +9 V DC input tip directly to the system's +5 V VCC rail and placed the 7905 regulator on the negative return path to regulate the ground line 5.0 V below the positive rail! Because of this "positive-common" regulator topology, you must NEVER connect an Oric's power supply ground to the same DC power supply powering an external peripheral or monitor, or you will short out the 7905 regulator and send raw +9 V straight into the 6502A, ULA, and DRAM!
1 External Power Jack Spec
| Parameter | Oric-1 & Oric Atmos Spec |
|---|---|
| Input Voltage | +9.0 V DC (7.5 V–9.0 V Regulated Switching PSU recommended) |
| Current Rating | Minimum 600 mA – 1.0 A |
| Barrel Plug | 2.1 mm inner × 5.5 mm outer DC barrel jack |
| Polarity | CENTRE-POSITIVE (Tip = +9 V, Outer Barrel = Negative Return to 7905 In) |
Why the ZX Spectrum PSU Kills an Oric: Both sit on UK benches, both are 9 V, and both use a 5.5×2.1 mm plug — but the ZX Spectrum is Centre-Negative while the Oric is Centre-Positive! Always check polarity before plugging in.
2 How to Measure Rails Correctly
- Always clip your black DMM probe to a logic IC's GND pin (`Pin 20 of IC6 6522 VIA` or the outer shield of the RGB/Tape DIN socket) — NOT to the outer barrel of the 9 V DC input jack!
- Measured between `6502A Pin 8 (VCC)` and `6502A Pin 1/21 (VSS)`, you must read +4.85 V to +5.15 V DC.
- 7905 Pinout (`IC23` TO-220): Pin 1 = `GND (Logic V_CC/+5V bus!)`, Pin 2 (Middle/Tab) = `INPUT (Negative barrel from 9V jack)`, Pin 3 = `OUTPUT (Logic 0V VSS ground!)`. Because the metal tab of the 7905 is at −4 V relative to logic ground, never short the 7905 heatsink to the RF modulator shield!
3 16K Oric-1 (`4116`) vs 48K (`4164`) DRAM
- 48K Oric-1 & All Oric Atmos Boards: Populated with eight single-rail 4164 (64K×1, +5 V only) DRAMs (`IC12–IC19`).
- Rare 16K Oric-1 Boards: Populated with eight 4116 (16K×1) DRAMs that require an onboard DC-DC inverter stage for +12 V (Pin 8) and −5 V (Pin 1) alongside +5 V (Pin 9). If upgrading a 16K Oric-1 to 48K with 4164s, you must change the motherboard RAM link jumpers so +12 V/−5 V are removed from the DRAM sockets!
- Switching Regulator Upgrade: To replace the hot 7905 (`IC23`) with a cool-running negative switching module, you must use a negative-output 7905 drop-in (such as a Mornsun `K7805M-1000R3` wired in negative mode or a dedicated `7905` buck converter) — a standard positive 7805 TSR-1 buck converter will NOT work in the 7905 footprint without modifying the PCB tracks!
System Selector: Oric-1 vs. Oric Atmos
Toggle between the 1983 Oric-1 (16K/48K) and the 1984 Oric Atmos to compare keyboards, BASIC ROM v1.0 vs v1.1 bugs, and motherboard revisions.
Oric Atmos 48K 1984–1986 • Red & Black Styling • BASIC v1.1
Released in early 1984 to address criticisms of the Oric-1's calculator-style keyboard and ROM bugs, the Oric Atmos houses an electrically identical core motherboard (Issue 3 / Issue 4 PCB) inside a striking red-and-black ABS wedge case with full-travel Futaba / Stackpole mechanical plungers, an updated 16 KB BASIC v1.1 ROM, and a modified cassette input conditioner for cleaner tape loading.
Key ICs & Designators (Issue 3 / 4 PCB)
- IC3 (CPU): MOS / Rockwell / Synertek 6502A @ 1.00 MHz
- IC1 (Custom ULA): Ferranti / Mietec HCS10017 / HLA011A / HAP201 (40-pin DIP) — generates 40×28 `TEXT` and 240×200 `HIRES` serial attribute RGB video, divides the 12.00 MHz crystal down to 1.0 MHz CPU `Φ2`, and handles interleaved DRAM refresh
- IC6 (VIA): MOS / Synertek 6522A (`$0300–$030F`) — interfaces the AY-3-8912 sound chip, Centronics parallel printer port, cassette FSK input/output & motor relay, and keyboard row strobe
- IC5 (PSG): General Instrument AY-3-8912A (28-pin DIP) — 3-channel sound generator (`PING`, `SHOOT`, `EXPLODE`, `ZAP` built into BASIC!) + 8-bit keyboard column selector on I/O Port A
- IC4 (ROM): 16 KB Mask ROM (`BASIC v1.1`, `$C000–$FFFF`, 28-pin)
- IC12–IC19 (RAM): 8× 4164 (64K×1, +5 V) DRAMs (with the top 16 KB `$C000–$FFFF` shadowed under the BASIC ROM and unlocked by disk interfaces using `/MAP`!)
- IC7 (Audio Amp): LM386N-1 driving the internal piezo/moving-coil speaker
Oric-1 vs Oric Atmos Hardware & ROM Comparison
| Feature | Oric-1 (1983) | Oric Atmos (1984) |
|---|---|---|
| Keyboard Type | 57 hard plastic "chiclet" keys over PCB dome contacts | 58 full-travel mechanical keycaps (with new FUNCT key!) |
| ROM Version | Tangerine BASIC v1.0 (`24-pin` or `28-pin`) | Oric Extended BASIC v1.1 (`28-pin`) |
| Tape Error Checking | Buggy in v1.0 (prints false errors or ignores checksums) | Fixed checksum routines & improved schmitt-trigger input |
| 64KB Overlay RAM | Present on all 8×4164 48K boards (16K hidden under ROM) | Present on all Atmos boards (unlocked by Microdisc / Erebus) |
| Dual-ROM Switcher | Can add v1.1 ROM for Atmos games | Many French/UK Atmos owners fit a 27C256 Dual-ROM (v1.0 + v1.1) for 100% Oric-1 game compatibility! |
Oric-1 (16K & 48K) 1983 • Pale Blue / Grey Chiclet Keys • BASIC v1.0
Conceived by Paul Johnson and Dr Barry Muncaster at Tangerine Computer Systems (Cambridge) to challenge the ZX Spectrum, the Oric-1 offered a fast 1 MHz 6502A, a proper 3-channel AY-3-8912 sound chip, a built-in Centronics printer port, and RGB output as standard. Over 160,000 Oric-1s were sold in 1983 across the UK and France (where Oric became a household name and later continued as the Oric Telestrat).
Oric-1 BASIC v1.0 Quirks & Fixes
- 24-Pin vs 28-Pin ROM Socket (`IC4`): Early Issue 1/2 Oric-1 boards sometimes populate two 8 KB ROMs (`IC4` & `IC20`) or a single 16 KB ROM. Later Issue 3 boards use a single 28-pin socket at `IC4`.
- The Infamous `TAB` & `ELSE` Bugs in v1.0: BASIC v1.0 had several well-known bugs in `HIRES` mode, `ELSE` statements, and cassette header verification that were patched in Atmos BASIC v1.1.
- Upgrading an Oric-1 to Dual BASIC v1.0 / v1.1: Burn a 27C256 (32 KB EPROM) with Oric-1 v1.0 in the lower 16 KB (`$0000–$3FFF`) and Atmos v1.1 in the upper 16 KB (`$4000–$7FFF`), bend out Pin 27 (`A14`), and wire it to a miniature SPDT toggle switch (+5 V via 4.7 kΩ pull-up vs GND)!
Oric-1 Chiclet vs Atmos Mechanical Keyboard Service
| Keyboard | Construction & Repair Procedure |
|---|---|
| Oric-1 Chiclet Keyboard | Uses a single-sided sub-PCB with stainless-steel tactile snap-domes taped over copper tracks, connected to the mainboard by a rigid 14-way ribbon jumper. Fix for dead/repeating keys: Desolder or unplug the keyboard ribbon before lifting the top shell too far (the solid-core ribbon snaps easily!), peel back the clear adhesive carrier sheet, and clean tarnished copper contact rings and snap-domes with a pencil eraser and 99% IPA. |
| Oric Atmos Keyboard | Uses individual mechanical switches soldered to a keyboard PCB via a 16-way flexible cable (includes the extra `FUNCT` wire). Clean bouncing switches by wicking a drop of DeoxIT D5 down the plunger stem and tapping 40 times. |
Diagnostic Checklist & IC12–IC19 DRAM Locator
Decoding the Oric's power-on black-and-white vertical bars, isolating HCS10017 ULA vs 4164 DRAM faults, and testing AY-3-8912 sound.
"Black & White Vertical Bars" on Boot & IC12–IC19 4164 DRAM Locator
When you power on an Oric-1 or Oric Atmos, the HCS10017 ULA (`IC1`) immediately begins scanning screen RAM (`$BB80–$BFDF`) before the 6502A CPU clears it — which is why every Oric briefly displays a screen of thick black-and-white vertical bars for ~0.5 seconds before clearing to the white/black `ORIC EXTENDED BASIC` prompt! If the machine stays frozen on the black-and-white vertical bars (or shows coloured/corrupted blocks), use this decision tree:
IC12–IC19 4164 DRAM Bit-to-IC Map (Issue 3 / 4 PCB)
| Data Bit | Oric DRAM IC | Visual Symptom When Stuck High / Low |
|---|---|---|
| Bit 0 (D0) | IC12 | Rightmost pixel of every 6-pixel character cell stuck on/off; ASCII bit 0 flipped (`A` → `@`) |
| Bit 1 (D1) | IC13 | 2nd pixel from right stuck; ASCII bit 1 flipped (`A` → `C`) |
| Bit 2 (D2) | IC14 | 3rd pixel from right stuck; colour attribute codes change to wrong ink/paper |
| Bit 3 (D3) | IC15 | 4th pixel from right stuck; flash/double-height serial attributes triggered randomly |
| Bit 4 (D4) | IC16 | 5th pixel from right stuck; numbers turn into letters |
| Bit 5 (D5) | IC17 | Leftmost pixel of every character cell stuck; serial attribute vs character mode bit corrupted! |
| Bit 6 (D6) | IC18 | Every character cell turns into a coloured/flashing attribute block (`Bit 6 = 0` means Attribute!) |
| Bit 7 (D7) | IC19 | Entire screen inverted (Black on White / Inverse video bit 7 stuck on!) |
Why Frozen Vertical Bars = Good ULA!
- Good News: If you see clean, steady black-and-white vertical bars on screen, your HCS10017 ULA (`IC1`) video timing, 12 MHz crystal, and RGB/PAL video output are WORKING!
- Check 6502A Reset (`Pin 40`) & Clock (`Pin 37`): Probe 6502A Pin 40 (`/RES`) to verify capacitor `C21` (10 μF) isn't holding the CPU in reset, and verify 1.0 MHz `Φ0` clock from ULA Pin 15.
- Check the Two 74LS257 Address Multiplexers (`IC10` & `IC11`): Positioned right beside the 8 DRAM chips. A failed 74LS257 (especially Texas Instruments or Fujitsu batches from 1983) prevents the CPU from reading Zero-Page/Stack RAM (`$0000–$01FF`), freezing the machine on the initial vertical bars!
- Swap / Socket the BASIC ROM (`IC4`): A dead mask ROM at `IC4` also freezes the machine on the initial power-on bars. Or plug in an external Erebus / Microdisc (which disables internal ROM via `/ROMDIS`) containing a diagnostic ROM!
HCS10017 ULA Failure & "Constant Beep" Diagnosis
Pure black screen (no sync, no vertical bars) or a continuous tone/buzz from the internal speaker on power-up.
- Why the Oric Screams/Buzzes on a Failed Boot: When the AY-3-8912 (`IC5`) powers up, its internal tone/noise registers contain random uninitialised values until the 6502A executes the BASIC ROM reset routine (which silences the AY via the 6522 VIA). Therefore, a constant tone on boot simply means the 6502A crashed before reaching the VIA/AY initialisation code (usually due to bad RAM `IC12–IC19`, bad 74LS257 `IC10/11`, or bad ROM `IC4`)!
- True ULA Failure (`IC1` — `HCS10017` / `HLA011A` / `HAP201`):
- If the 12 MHz crystal (`X1`) is oscillating into ULA Pin 2, +5 V is present on ULA Pin 40 (and GND on Pin 20), but there is no 1 MHz clock on ULA Pin 15 (`PHI`) and no 15.6 kHz sync on ULA Pin 17 (`SYNC`), the ULA has failed.
- Always clean the 40-pin ULA socket and stick a low-profile aluminium heatsink on top of `IC1`.
- Modern Drop-In Replacement: The community open-source Harlequin / CPLD Oric ULA replacement drops straight into the 40-pin `IC1` socket!
Sound (`AY-3-8912` / `LM386`) & Keyboard (`6522 VIA`) Testing
No keyclick, `PING` / `EXPLODE` commands are silent, or entire keyboard rows/columns don't respond.
- Quick Audio Test in BASIC: Type
PINGorZAPand press RETURN. - Sound Present on RGB DIN (Pin 2), Silent on Internal Speaker: Proves the AY-3-8912 (`IC5`) is healthy! Check the 8-pin LM386N-1 audio amplifier (`IC7`), coupling capacitor `C10`, or measure the underside loudspeaker voice coil (~8–16 Ω).
- Both Sound AND Keyboard Dead:
- On the Oric, the 6522 VIA (`IC6`) drives the 8 keyboard rows (via a `74LS145` BCD-to-decimal decoder or direct port lines) AND controls the AY-3-8912 (`IC5`) (whose 8-bit I/O Port A selects the 8 keyboard columns!) while comparing the result on `6522 PB3`.
- If the machine boots to `Ready` with a blinking cursor, swap the socketed AY-3-8912 (`IC5`) or 6522 VIA (`IC6`) to restore both audio and keyboard scanning!
5-Pin DIN RGB Video to SCART / Upscaler Guide
Why a passive Oric RGB cable shows a dark or rolling picture on modern TVs — and how to wire the active emitter-follower SCART buffer.
5-Pin DIN RGB Socket Pinout DIN 180° • Viewed Looking at Rear Socket
The Oric-1 and Oric Atmos output RGB, Composite Sync, and Mono Audio on a standard 180° 5-pin DIN socket (`RGB`). However, the R/G/B outputs inside the Oric are driven through high-impedance 1 kΩ series resistors straight from the ULA, and there is NO +5 V/+12 V pin on the RGB DIN socket to trigger SCART Pin 16 (RGB fast-blanking)!
| DIN-5 Pin (180°) | Oric Signal | Internal Source / Impedance | SCART Target Pin |
|---|---|---|---|
| Pin 1 | RED | ULA Pin 19 via 1 kΩ (`R27`) | SCART Pin 15 (Red In) |
| Pin 2 (Center) | GND (0 V) | Logic 0 V ground (output of 7905!) | SCART Pins 4, 5, 9, 13, 17, 18, 21 |
| Pin 3 | CSYNC (Composite Sync) | ULA Pin 17 via 1 kΩ (`R25`) | SCART Pin 20 (Composite Sync In) |
| Pin 4 | GREEN | ULA Pin 21 via 1 kΩ (`R26`) | SCART Pin 11 (Green In) |
| Pin 5 | BLUE | ULA Pin 22 via 1 kΩ (`R24`) | SCART Pin 7 (Blue In) |
Where to Tap Audio for Your SCART Cable: Notice that all 5 pins of the Oric's `RGB` DIN socket are used by `R, G, B, CSYNC, and GND`! For audio, run a twin fly-lead into the adjacent 7-pin `TAPE` DIN socket (Pin 3 = Line Audio Out, Pin 2 = GND) to feed SCART Pins 2 & 6!
Schematic Active RGB Buffer & SCART Pin 16 Blanking
When a 75 Ω SCART TV or OSSC/RetroTINK terminates the Oric's 1 kΩ internal RGB resistors, the voltage divider (`75 / 1075`) crushes the 5 V TTL signal down to just 0.35 V p-p (half brightness!). You can fix both the dim picture and the missing SCART Pin 16 RGB switch in two ways:
Option A: Using OSSC / RetroTINK 5X / 4K (No External Power Needed!)
====================================================================
* Wire DIN Red, Green, Blue, CSYNC, and GND straight to SCART.
* Manually select "RGBS (SCART)" input on the OSSC / RetroTINK
and raise Pre-ADC Gain to compensate for the 1kOhm internal resistors!
Option B: For CRT SCART TVs (Driving SCART Pin 16 RGB Blanking)
====================================================================
Tap +5V from Pin 34 of the Expansion Bus (or USB 5V ONLY if isolated
via a 100R resistor to SCART Pin 16 & Pin 18 — NEVER tie an external
non-isolated PSU ground to Oric GND if powered from the same strip!):
+5V (Exp Pin 34) o----[ 150 Ohm ]----o SCART Pin 16 (Forces RGB Mode!)
Oric GND (Pin 2) o-------------------o SCART Pins 4, 5, 9, 13, 17, 18
Internal 1 kΩ Resistor Bypass Mod: For full 0.7 V p-p RGB brightness without an active transistor cable, many Oric owners solder three 470 Ω resistors in parallel across the internal `R25, R26, R27` (1 kΩ) RGB output resistors on the motherboard (bringing them down to ~320 Ω)!
Cassette 7-Pin DIN & 34-Pin Expansion Port Pinouts
Wiring the 7-pin DIN Tape/Audio socket and the 34-way Microdisc / Cumana / Erebus / Twilighte expansion bus.
7-Pin DIN Cassette & Audio Output Port DIN 270° (`TAPE`)
Accepts a standard 5-pin 180° DIN plug in its central 5 pins (for tape EAR/MIC/GND) while using the two extra bottom pins (Pins 6 & 7) for the internal cassette motor relay (`REMOTE`):
| DIN-7 Pin | Signal | 3.5 mm / 2.5 mm Target Plug |
|---|---|---|
| Pin 1 | TAPE OUT (to Recorder MIC) | Red/Black 3.5 mm Tip (`SAVING`) |
| Pin 2 (Center) | GND (0 V) | 3.5 mm Sleeve (Common Ground) |
| Pin 3 | AUDIO OUT (AY-3-8912 Line Out!) | Tap this pin for clean external sound to your SCART cable or speakers! |
| Pin 4 | TAPE IN (from Recorder EAR) | White/Green 3.5 mm Tip (`CLOAD` — needs ~1.5 V p-p high volume!) |
| Pin 5 | NC | Unconnected |
| Pin 6 & Pin 7 | Cassette Motor Relay Contacts | 2.5 mm Sub-mini `REM` plug (closed during `CLOAD` / `CSAVE`) |
Best Place to Tap Audio for a SCART Cable: Because the 5-pin RGB DIN does not carry audio on a dedicated pin on all Oric revisions, tapping Pin 3 (`AUDIO OUT`) and Pin 2 (`GND`) of the 7-pin `TAPE` DIN socket gives you crystal-clear line-level AY-3-8912 sound for your TV!
34-Pin Rear Expansion Bus (`EXPANSION`) 2×17 IDC Header
Connects the Oric Microdisc, Cumana Disk Interface, Jasmin, Erebus (TAP/DSK SD-card loader), or Twilighte / Locus boards directly to the 6502A bus:
| Pin (Odd) | Signal | Pin (Even) | Signal |
|---|---|---|---|
| 1 | /MAP (Pull low to replace ROM `$C000` with internal 16K overlay RAM!) | 2 | D0 |
| 3 | /ROMDIS (Pull low to disable internal 16K BASIC ROM `IC4`) | 4 | D1 |
| 5 | Φ2 (1.0 MHz CPU Phase 2 Clock) | 6 | D2 |
| 7 | R/W (CPU Read / Write) | 8 | D3 |
| 9 | /IO (`$0300–$03FF` Page 3 I/O Strobe) | 10 | D4 |
| 11 | /IOCTRL (Pull low to disable internal 6522 VIA at `$0300`!) | 12 | D5 |
| 13 | A15 | 14 | D6 |
| 15 | A13 | 16 | D7 |
| 17 | A12 | 18 | A14 |
| 19 | A10 | 20 | A11 |
| 21 | A8 | 22 | A9 |
| 23 | A6 | 24 | A7 |
| 25 | A5 | 26 | A4 |
| 27 | A3 | 28 | A2 |
| 29 | A1 | 30 | A0 |
| 31 | −5 V / NC | 32 | /NMI (Non-Maskable Interrupt) |
| 33 | /IRQ (Interrupt Request) | 34 | +5 V DC / GND (Note: Pin 34 = GND on Issue 3/4; check schematic before drawing power!) |
How `/MAP` (Pin 1) & `/ROMDIS` (Pin 3) Unlock Full 64KB RAM: Although the Oric Atmos is advertised as "48K", it actually has 64 KB of 4164 DRAM installed! When a Microdisc or Cumana drive pulls Pin 1 (`/MAP`) low, the HCS10017 ULA unmaps the internal BASIC ROM at `$C000–$FFFF` and exposes the hidden top 16 KB of DRAM so Sedoric / Oric DOS can run in a full 64 KB RAM space!
Chip & EPROM Reference
Interactive IC Pinout Finder cards plus HCS10017 ULA and BASIC v1.0 / v1.1 EPROM upgrade notes.
MOS / Rockwell 6502A
IC3 — 1.00 MHz 8-bit microprocessor driving the Oric-1 and Oric Atmos.
View Pinout →MOS 6522A VIA
IC6 (`$0300–$030F`) — Versatile Interface Adapter controlling the AY-3-8912 bus, Centronics printer, keyboard rows, and tape I/O.
View Pinout →AY-3-8912A PSG
IC5 — 3-channel programmable sound generator AND 8-bit keyboard column scanner (I/O Port A).
View Pinout →4164 DRAM (×8)
IC12–IC19 (48K Oric-1 & Atmos) — Single-rail +5 V 64K×1 dynamic RAM providing 48K main + 16K overlay RAM.
View Pinout →4116 DRAM (×8)
IC12–IC19 (16K Oric-1 only) — Triple-rail (−5 V, +12 V, +5 V) 16K×1 dynamic RAM.
View Pinout →Oric Custom ULA (`IC1`) Part Number Cross-Reference
All three part markings found in `IC1` across Oric-1 and Oric Atmos production are 100% pin-for-pin identical:
| ULA Marking | Manufacturer | Notes |
|---|---|---|
| HCS10017 | Hughes / Plessey / Ferranti | Most common marking on both Oric-1 and Oric Atmos boards. |
| HLA011A / ULA1O10P | Ferranti / Mietec | Early Oric-1 marking; identical pinout and serial attribute logic. |
| HAP201 / 10017 | Late Production | Found on late 1984/85 Atmos and Eureka/Nova 64 units. |
BASIC ROM (`IC4`) EPROM Substitution & Jumper Links
On Issue 3 and Issue 4 motherboards, the 28-pin ROM socket at `IC4` is surrounded by solder jumper pads that configure it for either a 28-pin mask ROM (`23128`) or a standard 27C128 / 27C256 UV EPROM:
| EPROM Type | Size | Installation & Link Notes |
|---|---|---|
| 27C128 (16 KB, 28-Pin) | 16 KB | Direct 28-pin fit! Check that Pin 27 (`/PGM`) and Pin 28 (`+5V`) are tied high via the motherboard ROM links (or bend out Pin 27 if the board routes an inverted enable signal there and tie Pin 27 to Pin 28 `+5V`). |
| 27C256 (32 KB, 28-Pin) (Dual v1.0 / v1.1 Switcher) |
32 KB | Burn `BASIC10.ROM` (`16KB`) into `$0000–$3FFF` and `BASIC11B.ROM` (`16KB`) into `$4000–$7FFF`. Lift Pin 27 (`A14`), solder a 4.7 kΩ pull-up resistor from Pin 27 to Pin 28 (`+5V`), and wire a switch from Pin 27 to Pin 14 (`GND`) to toggle between Oric-1 and Atmos modes! |
Resources & Further Reading
Blog posts, interactive bench tools, and essential Oric-1 & Atmos communities.
Smiggy's Oric & 6502 Posts
Bench Tools & Machine Hubs
- IC Pinout Finder — 6502, 6522, AY-3-8910, 4164, 4116 & more
- Recap Planner — capacitor replacement guide
- Ohm's Law Calculator
- C64 Machine Hub — Commodore 64 reference
- C128 Machine Hub — C128, C128D & DCR reference
- SX-64 Machine Hub — Executive Portable C64 reference
- Amiga Machine Hub — A500/A600/A1200 reference
- Atari ST Hub — 520ST, 1040STFM & STE reference
- Apple IIe Hub — Unenhanced, Enhanced & Platinum reference
- BBC Micro Hub — Model B, B+ & Master 128 reference
- Acorn Atom & Electron Hub — Atom & Electron reference
- ZX Spectrum Hub — 16K/48K & +2/+3 reference
- Sinclair QL Hub — 68008, Microdrive & ULA reference
- Dragon 32/64 Hub — Dragon 32 & 64 reference
- Amstrad CPC 464 Hub — CPC 464 & Datacorder reference
- Osborne 1 & Kaypro II Hub — CP/M luggable reference
- Amstrad CPC 6128 Hub — 128K & 3″ disc reference
- MSX Machine Hub — MSX1, MSX2, MSX2+ & Turbo R reference
- Big-Box Amiga Hub — A1000, A2000, A3000 & A4000 reference
- Atari 8-Bit Hub — 400/800, 800XL & 130XE reference
- VIC-20 Machine Hub — Commodore VIC-20 reference
External Oric Resources
- Defence-Force Oric Community — the premier active Oric-1/Atmos hardware, repair, and demoscene forum
- Oric.org — complete Oric software, tape `.TAP`/`.DSK` archive, and service manuals
- Oric Service Manual & Schematics — official Tangerine fault-finding flowcharts and Issue 3/4 layouts
- Retroleum Oric Repair Guide — 7905 PSU topology, ULA pinout, and DRAM diagnostics