What this tester does

Fast, reliable testing of memory chips from the late 70s to early 90s — from 8-bit to 32-bit era systems like C64, C128, Amiga, Atari, ZX Spectrum, BBC Micro, Apple IIe and many more.

Insert a chip, set the DIP switch to match the pin count, hit reset. The tester auto-detects the chip type and runs the complete diagnostic suite. No menus, no algorithm selection, no datasheet lookups. The result appears on the OLED display or as a green/red LED — clear pass/fail because a defective memory chip can't be repaired anyway.

Normal test, ZIF socketStandard 16/18/20-pin chips like 4164, 41256 or 514256

Normal test, ZIP socket20-pin ZIP packages like 514256 or 514400

Self-test modeBuilt-in hardware verification with QR code link to docs

Key features

Zero test configuration

Set the pin count via DIP switch — the tester auto-detects the chip type and runs all tests automatically. No selecting algorithms, no menus, no datasheet lookups.

Fast

Full test in under 8 seconds for a 41256. Test a whole tray of chips in minutes.

Thorough by default

Memory patterns, crosstalk, address line verification, retention time, CAS-Before-RAS refresh, Fast Page Mode, Static Column Mode, ground short detection. Same chip → same diagnosis, always.

Safe

Short-circuit protection, current limiting, ground short detection. Self-test mode included to verify the tester hardware itself.

Practical

Broken is broken. You get a clear good/bad result with large readable feedback. No confusing diagnostic details for chips that can't be repaired anyway.

Fully open source

Hardware, firmware, schematics on GitHub under GPLv3. Every test claim is verifiable in the source code. No black box.

Real fault detection

The tester doesn't just say "good" or "bad" — it pinpoints the actual fault. The examples below show simulated fault scenarios to demonstrate what the tester detects:

Dout shorted to GNDDetected during the GND short pre-test

Dout shorted to VccIdentified through write/verify mismatch

Address pins shorted togetherCaught by bit-independence verification

Address pin stuck low (internal chip fault)

Address pin stuck at GNDInternal chip fault detected via address sweep

Pin connected to GND through 4.7k resistor

Soft fault: pin via 4.7k to GNDEven high-impedance address faults are detected

Test of a 4116 chip on the 4116 adapter board

4116 chip via adapter boardMulti-voltage adapter for 4116 and 4027 DRAM

Half-good 4164 chips

A common scenario in retro repair: 4164 chips where one or more of the four quadrants failed. Historically, such chips were remarketed as 32K×1 (3732 or 4532) depending on which half remained functional. The tester optionally identifies these cases — useful when you actually need 32K chips, configurable when you don't.

Fully functional 4164Labeled as 3732 or 4532 — but actually tests as a complete, fully working 4164

3732 that can also be used as 4532 when one quadrant is defective

3732 usable as 4532One quadrant defective — chip works in either 3732 or 4532 configuration

Supported chips & test times

Test times are for the complete comprehensive test — including pattern tests, retention check, CAS-Before-RAS refresh, Fast Page Mode, Static Column Mode, and address line verification. Times shown are for current firmware; ongoing firmware development continues to improve speed and add chip support.

Chip	Capacity	Test time	Mode	Notes
4816	16K × 1	1.6 s	Fast Page
3732 / 4532	32K × 1	2.8 s	Fast Page	Half-good 4164 chips
4164	64K × 1	2.8 s	Fast Page	C64, ZX Spectrum, many more
41256	256K × 1	7.4 s	Fast Page
41257	256K × 1	7.4 s	Nibble Mode	Burst variant of 41256
4416	16K × 4	4.2 s	Fast Page
4464	64K × 4	6.4 s	Fast Page
411000	1M × 1	25.9 s	Fast Page
44256 / 514256	256K × 4	4.1 s	Fast Page	DIP & ZIP package
44258	256K × 4	4.1 s	Static Column	Static column variant of 44256
514400	1M × 4	12.8 s	Fast Page	DIP & ZIP package
514402	1M × 4	12.8 s	Static Column	Static column variant of 514400
4027 *	4K × 1	1.3 s	Fast Page	* Requires 4116 adapter board
4116 *	16K × 1	1.6 s	Fast Page	* Requires 4116 adapter board

2114 SRAM support and additional chip types are in active firmware development.

Where to buy

Available directly from the developer — pre-assembled SMD board, fully tested, ready to solder the through-hole components (approximately 30 minutes).

SMD RAM Tester

eBay

EU & UK with IOSS, USA with PDDP

Lectronz

Worldwide — EUR pricing

AmiBay

Active retro community marketplace

SMD 4116 Adapter Board

Required for testing 4027 and 4116 DRAM chips. Generates the +12V and −5V rails with built-in protection.

eBay

Standalone listing or as combo

Lectronz

Worldwide — EUR pricing

AmiBay

Active retro community marketplace

      No surprise fees: EU and UK customers pay import VAT at checkout via eBay's IOSS — no customs handling charges at delivery. USA shipping uses Swiss Post PDDP — all duties prepaid.
    

Want to build it yourself?

Both the SMD and through-hole versions are available as community PCB projects on PCBWay. All Gerber files, schematics and firmware are on GitHub.

→ Build it yourself on GitHub

Open source

All schematics, PCB files, firmware source code and test algorithms are public on GitHub under GPL v3. Any test claim made on this site can be verified by reading the source code.

This is a deliberate choice: diagnostic equipment is more useful when its methodology is auditable. Users can confirm that the documented tests actually run as described, identify limitations, and modify the firmware for their own use cases.

Pull requests, issues and forks are welcome.

→ Visit the GitHub repository

      Buying directly supports continued development. Firmware updates, support for additional chip types, and ongoing documentation are funded through sales. Buying from the developer means you support the project — not a reseller.
    