Commodore 64 Machine Hub

Board reference, diagnostics, IC pinouts and repair resources — everything you need on the workbench when servicing a C64.

Motherboard ASSY Selector

Select your board revision to view the electrolytic capacitor list and IC layout.

Commodore 64 Board Recap Guide & Electrolytic Capacitor ReferencePrint or save a single-page bench reference for C64 ASSY 250407, 250425, 250466 & 250469 boards.

ASSY 250407 Rev A & B — 1982–83

The original "longboard" motherboard found in early breadbin C64s. Uses discrete 4116 DRAM (16×1-bit, 8 chips), a 5-pin DIN A/V connector, and the original 82S100 PLA. Requires all three voltage rails from the PSU: +5 V DC, +12 V DC, and 9 V AC.

Key ICs

  • CPU: MOS 6510
  • VIC-II: MOS 6567 (NTSC) / 6569 (PAL)
  • SID: MOS 6581
  • CIA ×2: MOS 6526
  • PLA: 82S100 / 906114-01
  • DRAM: 8× 4116 (16K×1)
  • Colour RAM: 2114 (1K×4 SRAM)

Electrolytic Capacitor List

RefValueVoltageNotes
C1100 µF10 VMain filter
C2100 µF10 VMain filter
C31100 µF25 V12 V rail filter
C361000 µF10 V5 V bulk
C4822 µF25 VVIC-II filter
C8810 µF16 VSID filter
C91470 µF16 VAudio decoupling
C9510 µF16 VCassette port
C105220 µF10 VRF modulator

Replace with 105 °C low-ESR electrolytics. Consider adding extra ceramic bypass caps near the DRAM bank.

Original PSU Danger Warning

The Commodore 64 power supply (C64 PSU, part 251053-02) is a known failure point that can destroy your machine. When the internal 5 V regulator fails, it often fails short, sending unregulated voltage (7–9 V DC) directly into the C64, killing the CPU, SID, CIAs, and potentially the VIC-II.

DIN 7-Pin Power Connector Pinout

PinSignalSpec
1GNDGround
2GNDGround
3+5 V DCRegulated, 1.5 A max
4+5 V DCRegulated, 1.5 A max (ganged with pin 3)
59 V AC~1 A (for TOD clock & user port)
69 V ACReturn
7+5 V DCSense (some boards)

Modern Replacement Options

  • C64 PSU Mark II (Electroware) Switch-mode, built-in over-voltage protection. The most popular aftermarket option.
  • Ray Carlsen C64 Saver / PSU Hand-built by Ray Carlsen, gold-standard quality. Also available as a "saver" inline fuse that protects against 5 V overvoltage.
  • Keelog C64 PSU Compact switch-mode replacement with LED indicator. CE-certified.
  • DIY: MeanWell RT-50B + Transformer Build your own with a MeanWell 5 V / 12 V supply and a 9 V AC mains transformer. Add a crowbar/fuse on the 5 V rail.

Tip: Always measure the 5 V DC rail with a multimeter before powering on a C64 with an untested PSU. If it reads above 5.4 V, do NOT connect it.

Common Fault Checklist

Quick diagnostic reference for the most frequent Commodore 64 failures.

■

Black Screen (No Border)

Power LED on, but display is completely black — no border colour, no cursor.

Diagnostic Steps

  1. Verify PSU voltages: +5 V DC and 9 V AC present at the power connector.
  2. Check the CPU (6510) — verify power-on reset release on Pin 40 and the Φ2 clock (~0.985 MHz PAL / 1.023 MHz NTSC on Pin 39).
  3. Check the PLA (82S100) — the most common single point of failure. Swap with known-good or probe chip selects.
  4. Test DRAM: swap individual 4116/4164 chips or use a dead-test cartridge.
  5. Check the ROMs: BASIC (901226-01) and KERNAL (901227-03). Verify CS and data lines.
▦

Garbled Video / Wrong Colours

Border visible but screen shows random characters, colour bleeding, or wrong colour palette.

Diagnostic Steps

  1. Border present = CPU & PLA working. Focus on video path and RAM.
  2. Colour RAM (2114 SRAM) — wrong or missing colours indicate colour RAM failure. Check U6.
  3. DRAM failures often show repeated characters or "checker" patterns — use a dead-test cartridge to identify the faulty chip.
  4. VIC-II failure can cause distorted or missing video output. Check for hot VIC-II chip.
  5. Character ROM (901225-01) failure causes garbage characters with correct colours — inspect your dumped EPROM or Koala/Art Studio screens in the Retro Graphics & Screen Viewer.
⚙

PLA Failure

Black screen, flashing screen, random crashes, or the machine runs hot with no display.

Diagnostic Steps

  1. Touch the PLA chip (U17) — if it is extremely hot to touch, it is likely failing or already dead.
  2. The original 82S100 / 906114-01 PLA is the single most failure-prone chip in the C64 due to heat stress.
  3. Swap with a known-good PLA or install a modern replacement: PLAnkton, SuperPLA, or CPLD-based alternatives.
  4. A dead PLA will prevent the CPU from accessing ROM and RAM — resulting in a completely dead machine.
  5. Modern replacements run much cooler and are highly recommended even as a preventative upgrade.
♫

Dead SID (No Audio)

Machine boots normally with video output, but produces no sound through the A/V port or RF output.

Diagnostic Steps

  1. Test audio output with a known working cable and monitor/TV.
  2. Check the audio coupling capacitor on the A/V port output path.
  3. Run a SID test program (e.g., SID Tester by Matthias) to exercise all three voices.
  4. SID chip (6581 / 8580) is sensitive to static discharge and overvoltage. Inspect for cracks or burns.
  5. Replacements: original pull, ARMSID, SwinSID, FPGASID. Note: 6581 and 8580 have different filter capacitor requirements — do not swap without changing the filter caps.

C64 IC Pinouts

Direct links to full pinout reference pages for every major IC in the Commodore 64.

DIP-40

MOS 6510

CPU — 8-bit processor with built-in I/O port. The heart of the C64.

View Pinout →
DIP-28

MOS 6581 SID

Sound Interface Device — 3-voice synthesiser with multi-mode filter. Longboard version.

View Pinout →
DIP-28

MOS 8580 SID

Revised SID for shortboard C64C. Different filter characteristics and lower voltage.

View Pinout →
DIP-40

MOS 6567/6569 VIC-II

Video Interface Chip — generates all video output, sprites, and handles DRAM refresh.

View Pinout →
DIP-40

MOS 6526 CIA

Complex Interface Adapter — keyboard scanning, joystick ports, serial bus, and TOD clock.

View Pinout →
DIP-28

82S100 PLA

Programmable Logic Array — memory map decoding and bank switching. #1 failure point.

View Pinout →
DIP-16

4116 DRAM

16K×1 dynamic RAM — used in early longboard C64s. Needs ±5 V and +12 V.

View Pinout →
DIP-16

4164 DRAM

64K×1 dynamic RAM — replaced 4116 in later breadbin boards. +5 V only.

View Pinout →
DIP-18

41464 / 4464 DRAM

64K×4 nibble-wide DRAM — just two chips (U10/U11) provide 64 KB on C64C shortboards.

View Pinout →
DIP-16

MOS 8701 Clock Gen

U31 (ASSY 250425/250466) — generates Color Clock and Dot Clock from a single crystal.

View Pinout →

A/V & Serial Port Pinouts

Reference pinouts for the C64 audio/video and IEC serial bus connectors.

8-Pin DIN A/V Port C64C / Shortboard

Found on ASSY 250466 and 250469 boards. Supports S-Video (separate luma/chroma) and composite. Full interactive diagram & S-Video SCART guide →

PinSignalNotes
1Luminance (Y)S-Video luma output
2GNDSignal ground
3Audio OutLine-level mono audio
4Composite VideoCombined luma + chroma (CVBS)
5Audio InDirectly connected to SID ext-in
6Chrominance (C)S-Video chroma output
7+5 V DC~50 mA max (directly from main rail)
8GNDShield / ground

Tip: For best picture quality, use pins 1 (luma) and 6 (chroma) with an S-Video cable. Composite (pin 4) combines both signals and introduces dot crawl.

5-Pin DIN A/V Port Breadbin / Longboard

Found on ASSY 250407 and 250425 boards. Composite and audio only — no native S-Video breakout.

PinSignalNotes
1Luminance (Y)Luma only (not true S-Video on most boards)
2GNDSignal ground
3Audio OutLine-level mono audio
4Composite VideoCombined CVBS signal
5Audio InSID external audio input

The 5-pin DIN can be modded for S-Video by tapping the chroma signal directly from the VIC-II and adding a 6th wire. Many "S-Video mod" guides exist for the longboard.

IEC Serial Bus Port DIN 6-Pin

The C64's serial bus for disk drives (1541, 1571), printers (MPS-801), and other peripherals. Active-low open-drain protocol. Full IEC bus pinout →

PinSignalNotes
1/SRQ INService Request (active-low)
2GNDSignal ground
3ATN OUTAttention (directly from CIA#1 PA3)
4CLKSerial clock (active-low, open-drain)
5DATASerial data (active-low, open-drain)
6/RESETActive-low system reset (directly from reset line)

Use shielded cable for IEC connections over 1 m. The serial bus speed is ~400 bytes/sec stock; fast loaders bypass this via CIA timing tricks.

C64 .D64 Disk Parser, 6502/6510 Disassembler & ROM Patcher (Rust/Wasm)

Inspect 1541 disk images, disassemble 6510 machine code with live C64 IC register cross-links, and verify/patch KERNAL & diagnostic EPROM dumps directly in your browser.

1541 .D64

.D64 BAM & Directory Parser

Inspect Track 18 BAM sector bitmaps, browse PETSCII directory entries, and extract .PRG files in one click.

Open .D64 Parser →
MOS 6510

6502 / 6510 Disassembler

Side-by-side hex & assembly view with automatic links to 6510, VIC-II, SID, CIA, PLA, and Colour RAM pinouts.

Open Disassembler →
ROM / .BIN

.BIN Patcher & CRC32 Verifier

Verify IEEE 802.3 CRC32 & 16-bit checksums on 901227-03 KERNAL / Dead-Test ROMs and apply hex byte patches.

Open ROM Patcher →
.KOA / .ART

Retro Graphics & Font ROM Viewer

Render C64 Koala (.KOA), Art Studio (.ART), and 901225-01 8×8 Character ROM dumps with Colodore VIC-II palettes and PNG export.

Open Graphics Viewer →

Resources & Further Reading

Blog posts, external references, and community links for Commodore 64 repair and restoration.

Smiggy's C64 Blog Posts

Bench Tools

External Resources

Commodore 8-Bit 1982 · 8-Bit Computers

Commodore 64 — Unified Workbench Reference

ASSY 326298 to 250469 board selector, PSU overvoltage protection, PLA & DRAM fault checklist, SID/VIC-II pinouts, and .D64/6502 Wasm lab.

CPU / Architecture MOS 6510 / 8500 @ 0.985 MHz
Memory (RAM / VRAM) 64 KB DRAM + 0.5 KB 2114 Colour
Capacitor Mount Through-Hole
Custom Chipset & Key ICs
MOS 6510 VIC-II 6569/8565 SID 6581/8580 82S100 PLA 6526 CIA 4164 DRAM
Capacitor & Power Stage Reference

Commodore 64 (C64) — Capacitor & Recap Reference

Board revisions, electrolytic capacitor lists, voltage/farad ratings, and Through-Hole servicing notes.

Commodore 64 (C64) — Printable Board Recap & Capacitor BOM ReferenceFormat this system's capacitor replacement list, diagnostic flowchart, and IC pinouts into a high-contrast bench PDF.

Commodore 64 — ASSY 250407

Early breadbin "long board" • Mount: Through-hole • Difficulty: Beginner friendly

Full Printable Recap Sheet →

Mainboard (19 Capacitors)

Ref Capacitance Voltage Package / Type Circuit Location & Bench Notes
C8 10 uF 25 V Radial
C12 10 uF 25 V Radial Fitted as an electrolytic on Rev B. Some revisions use a ceramic here - if yours is ceramic, leave it alone.
C13 10 uF 25 V Radial
C14 10 uF 25 V Radial
C15 10 uF 25 V Radial
C17 10 uF 25 V Radial
C19 2200 uF 16 V Axial Largest can on the board. Both sources list this as the 2200 uF axial - it is not a 470 uF part.
C24 10 uF 25 V Radial
C34 10 uF 25 V Radial
C57 10 uF 25 V Radial
C62 10 uF 25 V Radial
C65 10 uF 25 V Radial
C88 1000 uF 25 V Axial 470 uF on Rev B and earlier, 1000 uF on Rev C and later. Both sources ship 1000 uF for every revision, which is safe to fit throughout.
C90 470 uF 25 V Axial
C91 100 uF 16 V Radial
C94 10 uF 25 V Radial
C102 10 uF 25 V Radial
C107 10 uF 25 V Radial Rev C boards. Sits inside the VIC-II shielded area, so the shield has to come off to reach it.
C108 10 uF 25 V Radial Rev C boards. Also inside the VIC-II shielded area.
Printable Diagnostic Flowchart & Voltage CheckpointsFormat this step-by-step fault isolation tree into a high-contrast bench reference sheet.

Complete Diagnostic Flowchart: Commodore 64 Blank / Black Screen Fault Isolation (Commodore 64 (ASSY 326298 / 250407 / 250425 / 250466 / 250469))

STEP 1: Measure +5V DC Logic Rail at User Port Pin 2 or CPU Pin 6 [node-1]
Disconnect cartridges and serial cables. Set your digital multimeter to DC Volts. Place black probe on User Port Pin 12 (GND) or RF modulator chassis shield. Probe User Port Pin 2 (+5V DC) and MOS 6510 CPU (U7) Pin 6 (VCC).
Expected Reading: Steady +4.75V to +5.25V DC with <50 mVpp ripple. Above +5.25V indicates a failing epoxy brick regulator.
STEP 2: Check 9V AC Transformer Rail & VIC-II Pin 13 (+12V VDD) [node-2]
Switch multimeter to AC Volts and probe across User Port Pins 10 and 11 (9V AC from PSU through fuse F1). Switch back to DC Volts and probe VIC-II (U19) Pin 13 (VDD): expect +12.0V on 6567/6569 longboards (from 7812 VR1 & C88/C90) or +5.0V on 8562/8565 shortboards.
Expected Reading: 8.5V–11.0V AC on User Port Pins 10–11, and +11.4V to +12.6V DC at VIC-II Pin 13 (ASSY 250407–250466).
STEP 3: Verify Φ2 System Clock at CPU Pin 39 & /RESET at Pin 40 [node-3]
Probe MOS 6510 CPU (U7) Pin 40 (/RESET): must hold LOW (<0.4V) for ~400 ms at power-on (via 556 timer U20 & C24), then snap HIGH (>3.8V). Check Φ2 clock at CPU Pin 39 (and Φ0 input at Pin 1 from VIC-II Pin 17): verify a clean 0.985 MHz (PAL) / 1.023 MHz (NTSC) TTL square wave.
Expected Reading: Pin 40 (/RESET) steady HIGH (+4.8V); Pin 39 (Φ2) pulsing at 0.985 MHz (PAL) swinging 0.15V to 4.65V.
STEP 4: Probe 82S100 PLA (U17) Chip-Select Strobes (/CASRAM Pin 18 & /KERNAL Pin 16) [node-4]
Check thermal state of U17 (82S100 / 906114-01 PLA): if scorching hot (>60°C), suspect internal nichrome fuse degradation. Scope PLA Pin 18 (/CASRAM), Pin 16 (/KERNAL), and Pin 15 (/BASIC) during Φ2 high. Verify clean active-low strobes (<0.4V low, >3.8V high) without mid-rail (~1.8V–2.2V) runt contention steps.
Expected Reading: Crisp active-low pulses on /CASRAM (Pin 18) and /KERNAL (Pin 16). If Dead Test 781220 cartridge flashes border 1–8 times, PLA works and DRAM is faulty.
STEP 5: Isolate 4164 DRAM Bus Contention vs. KERNAL ROM / 6510 CPU [node-5]
Insert a C64 Dead Test (781220) cartridge or scope DRAM data pins D0–D7 across U9–U12 & U21–U24 (4164 Pin 2 Din / Pin 14 Dout). Does the Dead Test flash the screen border 1–8 times, or do you see a ~1.8V mid-rail contention plateau on a data line D0–D7?
Expected Reading: Yes = Faulty 4164 DRAM (or 74LS257 multiplexer U13/U25). No = Check KERNAL ROM (U4), 6510 CPU (U7), or shorted 6581 SID (U18) pulling bus down.
[ISOLATED FAULT: RES-PSU] Fault Isolated: +5V DC Supply Rail Out of Spec / Failing Brick PSU VERDICT
The mainboard is receiving an invalid or over-voltage +5V DC rail. Original epoxy-potted Commodore brick PSUs suffer internal 7805 thermal drift or short-circuit failure.
[ISOLATED FAULT: RES-9VAC-12V] Fault Isolated: Missing 9V AC or +12V VR1 (7812) / C88/C90 Rail Failure VERDICT
Without 9V AC or the derived +12V DC rail on ASSY 250407–250466, the NMOS 6567/6569 VIC-II cannot generate video sync or Φ0 clock.
[ISOLATED FAULT: RES-CLOCK-RESET] Fault Isolated: /RESET Stuck Low or Missing Φ2 / 8701 Dot Clock VERDICT
The 6510 CPU is either held permanently in reset (Pin 40 LOW) or lacks the 0.985 MHz Φ2 clock (Pin 39) generated by the 8701 (U31) and VIC-II (U19).
[ISOLATED FAULT: RES-PLA] Fault Isolated: Failed 82S100 / 906114-01 PLA (U17) VERDICT
The 82S100 PLA is failing to decode memory strobes (/CASRAM Pin 18, /KERNAL Pin 16, /BASIC Pin 15) or asserting multiple chip-selects simultaneously.
[ISOLATED FAULT: RES-DRAM] Fault Isolated: Bad 4164 DRAM (U9–U12 / U21–U24) or 74LS257 Mux (U13/U25) VERDICT
One or more 4164 (64K×1) DRAM chips—or the MOS-branded 74LS257 address multiplexers (U13/U25)—are corrupting lower zero-page/stack memory.
[ISOLATED FAULT: RES-ROM-CPU] Fault Isolated: KERNAL ROM (U4), MOS 6510 CPU (U7) or Shorted SID (U18) VERDICT
With rails, clock, PLA, and DRAM verified, the black screen is caused by a corrupted KERNAL ROM ($E000–$FFFF), a halted 6510 CPU, or a shorted 6581 SID locking the data bus.
Interactive Pinouts, Visualizers & Disassemblers

Commodore 64 (C64) — System Bench Tools & IC Pinouts

Click any chip below to open its interactive DIP/PLCC pinout diagram, pin-by-pin signal table, and oscilloscope test waveforms.

Commodore 64 (C64) — Printable IC Pinout & Chipset SummaryPrint this system's custom IC pinout summary or open any chip card below for its full DIP/PLCC pinout sheet.
DIP-14 74-Series Gates

74LS00

SN74LS00N / DM74LS00N

Quad 2-input NAND gate — the most common glue-logic part in retro computers.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS02

SN74LS02N / DM74LS02N

Quad 2-input NOR gate — outputs on pins 1, 4, 10 and 13, the opposite pin order from the 74LS00.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS04

SN74LS04N / DM74LS04N

Hex inverter — six independent NOT gates in one 14-pin DIP, the standard logic-level converter of the 74-series family.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS08

SN74LS08N / DM74LS08N

Quad 2-input AND gate — same 14-pin pinout as the 74LS00, with outputs high only when both inputs are high.

Open Interactive Pinout →
DIP-16 74-Series Decoders

74LS138

SN74LS138N / DM74LS138

3-to-8 line decoder with three enable inputs and eight active-low outputs — the classic memory-address decoder.

Open Interactive Pinout →
DIP-16 74-Series Decoders

74LS139

SN74LS139N / DM74LS139A

Dual 2-to-4 line decoder — two independent decoders, each with one active-low enable and four active-low outputs.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS14

SN74LS14N / DM74LS14N

Hex Schmitt-trigger inverter — six NOT gates with hysteresis, the standard cure for slow or noisy input edges.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS32

SN74LS32N / DM74LS32N

Quad 2-input OR gate — same 14-pin pinout as the 74LS00, with outputs high when either input is high.

Open Interactive Pinout →
DIP-14 74-Series Flip-Flops

74LS74

SN74LS74AN / DM74LS74A

Dual D flip-flop with asynchronous preset and clear (both active low) — the standard edge-triggered latch and divider of the 74-series.

Open Interactive Pinout →
DIP-14 74-Series Gates

74LS86

SN74LS86AN / DM74LS86A

Quad 2-input XOR gate — same 14-pin pinout as the 74LS00, with outputs high when the inputs differ.

Open Interactive Pinout →
DIP-16 4000-Series Buffers

CD4049

CD4049UB / MC14049 / HEF4049

Hex inverter/buffer — VDD on pin 1 and VSS on pin 8, the opposite end from every other part in this library; two NC pins.

Open Interactive Pinout →
DIP-14 4000-Series Switches

CD4066

CD4066B / MC14066 / HEF4066

Quad bilateral switch — four analogue/digital switches with independent controls; control pins are not adjacent to the switches they operate.

Open Interactive Pinout →
DIP-40 MOS 6500

MOS 6502

MOS 6502 / R6502 / UM6502

The 8-bit CPU at the heart of the Apple II, PET, VIC-20, BBC Micro and Atari 2600.

Open Interactive Pinout →
DIP-40 MOS 6500

MOS 6510

MOS 6510 / 8500

The Commodore 64 CPU — a 6502 core with a 6-bit I/O port and AEC bus-acknowledge pin.

Open Interactive Pinout →
DIP-40 MOS 6500 Peripheral

MOS 6522 VIA

MOS 6522 / SY6522 / R6522 / W65C22

Two 8-bit I/O ports, two 16-bit timers and a shift register — the 6502 family peripheral chip.

Open Interactive Pinout →
DIP-40 MOS 6500 Peripheral

MOS 6526 CIA

MOS 6526 / 6526A / 8521

Two 8-bit I/O ports, two timers, a time-of-day clock and a serial port — the C64 peripheral chip.

Open Interactive Pinout →
DIP-28 Programmable Logic

Signetics 82S100 FPLA

82S100 / 906114-01 / PLS100

The C64 PLA — 16 inputs, 8 outputs, 48 product terms. The most failure-prone part in a Commodore 64.

Open Interactive Pinout →
DIP-16 MOS Timing

MOS 8701 Clock Generator

MOS 8701 (251527-01)

The 16-pin master clock multiplier/divider in the Commodore 64 (ASSY 250425/250466) and Commodore 128 — generates Color Clock and Dot Clock from a single crystal.

Open Interactive Pinout →
DIP-40 MOS VIC-II

MOS 6567 / 6569 VIC-II

MOS 6567 / 6569 / 8562 / 8565

The Commodore 64 video chip — generates the display, the system clock and the DRAM timing.

Open Interactive Pinout →
DIP-28 MOS SID

MOS 6581 SID

MOS 6581 / 6581R4

The Commodore 64's sound chip — three-voice synthesiser with filter, envelope and paddle ADC.

Open Interactive Pinout →
DIP-28 MOS SID

MOS 8580 SID

MOS 8580 / 6582

The later C64/C128 sound chip — same pinout as the 6581 but 9 V supply and a cleaner filter.

Open Interactive Pinout →
DIP-18 Static RAM

2114 1K x 4 SRAM

2114 / 2114L / F2114 / TMM314 / UM2114

1024 x 4 static RAM — data pins numbered from ONE (DQ1-DQ4, no DQ0), used in pairs for byte-wide storage.

Open Interactive Pinout →
DIP-28 EPROM

2764 8K x 8 EPROM

2764 / 2764A / 27C64 / M2764A / HN482764

8K x 8 UV-erasable EPROM, the JEDEC 28-pin byte-wide standard. Same pinout as the 6264 SRAM except for four pins.

Open Interactive Pinout →
DIP-16 Dynamic RAM

4164 64K x 1 DRAM

4164 / MT4264 / TMS4164 / MB8264 / KM4164 / 41464 (x4)

64K x 1 DRAM, single +5 V. VCC is pin 8 and GND is pin 16 — the reverse of almost every other 16-pin DIP. Apply 5 V to pin 16 and it dies.

Open Interactive Pinout →
DIP-18 Dynamic RAM

4416 / 4464 (16K/64K x 4) DRAM

TMS4416 / MB81416 / TMS4464 / MT4067 / KM41464

The 18-pin nibble-wide (x4) DRAM family — just TWO chips replace eight 4116/4164 DRAMs! Upgrading 4416 to 4464 unlocks 64KB on the C16, C128 VDC, CoCo 2 and Atari 600XL.

Open Interactive Pinout →
DIP-8 555 Timer

NE555

NE555 / LM555 / SA555

The classic 555 timer — astable, monostable and bistable modes from a single 8-pin chip.

Open Interactive Pinout →
Visualizer

Signal & Trace Visualizer (Scope)

Compare healthy vs. faulty CPU clocks, reset ramps, PLA strobes, and 5V PSU ripple waveforms.

 Disassembler & ROM Lab

Retro File Utilities (Rust/Wasm)

6502/6510 disassembler with IC register links, C64 .D64 parser, and EPROM CRC32 verifier/patcher.

 Logic & Pinouts

Connector & Port Pinout Reference

59 interactive RGB SCART, DIN A/V, PSU polarity, joystick, floppy, and expansion bus pinouts.

 Logic & Pinouts

Logic & RAM Substitution Guide

Cross-reference 4116→4164 DRAM mods, 2364→27C256 EPROM adapters, and 74LS/74HCT swaps.

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