Below you can see all details of my 2-hours 2-dollar project 'DramArduino'.
It's simple and very handy DRAM chip tester. It works with 4164 and 41256 IC's.
Testing is not too fast but acceptable - 4 different passes are performed in about 80 seconds total.
Results are 100% reliable only if the test FAILS - you can throw away the chip without fear.
If the test passes, this doesn't certainly mean that it will work in Oric, because as you know Oric's are very 'sensitive' to DRAM.
Actually this was my goal exactly - to sort out the working chips from about 200 before I'm get bored .
Working with the tool is easy: place the chip in the ZIF socket, press small reset button, wait until GREEN LED blinks,
if it remains permanently on - chip is OK, if the chip is bad - RED LED lights.
If USB is connected, status is reported in your serial console. This helped me to detect some 'lazy' chips - they failed in
different, on every next test, growing addresses but when they become 'hot' test passes always.
IIRC such fail to boot Oric was reported somewhere in this forum...
Attached are 'schematic', source code and pictures - do with them what you want .
This is the right place to discuss on how to implement hardware vsync, adding a VIA or AY chipset, puting multiple roms, or how to design a new flash expansion card.
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