DRAM Tester for ZX Spectrum, C64, Oric, Jupiter Ace and other retro computers and equipment.
This DRAM tester supports 1 bit DRAM devices from 4Kbit to 256K bit (eg. MCM4096, M4027P, 4116, TMS4532NL3/4, M3723L/H, 4164, 4128, 41256, etc.).
Support for 4Kbit parts (e.g. M4027 & MCM4096)
Support for piggybacked DRAM such as Samsung KM4128 used in early PCs
Multicolour LED output to make the results simpler to read and more intuitive (e.g. working columns show as a horizontal bar, working rows as a vertical bar, fully working as a a square box)
It has a simple power requirement, needing just 5V and drawing less than 100mA, so it can be powered from any USB port with a standard micro-USB cable. The tester generates all of the required voltages (+3V3, +12V, +5V and -5V) from this single supply.
How to Use
Connect the board to a USB port to provide power
Put the DRAM chip in the correct socket: The left socket is for parts that require -5V on pin 1, +12V on pin8, +5V on pin 9 and 0V on pin 16 (e.g. MCM4096, M4027P, 4108 and 4116), all other types should ONLY be tested in the right socket.
Press the start button and wait for the result to show on the LEDs.
Please note that the LEDs will flicker while the DRAM is being tested, this is normal.
Good 4Kbit Block
Good 16Kbit Block
Good 64Kbit Block
The tester is pretty fast, based on a modern 32 bit ARM micro-controller running at 64MHz. Here are some examples of the test times for this tester:
Approximate Test Time
About 2 seconds
About 5 seconds
About 19 seconds
About 37 seconds
About 75 seconds
The tests are made such that the refresh period is close to the specified maximum retention time for the part being tested. That means close to 4ms for 64 rows on an M4027 or MCM4096, 2ms for 128 rows on a 4116 part and close to 4ms for the 256 rows on a 4164 or 41256 part. This ensures that any issues that only occur near to the maximum retention time are also detected by this tester. So you can be pretty sure that if a part tests as good in this tester then it should work well in a real application.
The Test Procedure
1. Measure the size of the DRAM. 2. High speed tests
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