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DRAMscope 1.6
⚠ Two fixes that matter if you are testing a RAM replacement board.
A single bad byte is no longer diagnosed as a PLA fault
ALL 8 BITS BAD - NOT ONE CHIP. SEE PLA was reached whenever the failing-bit mask hit $FF — and one byte coming back completely wrong does that. The screen delivered a systemic diagnosis with BAD BYTES 1 on the line above it.
All eight bits set is not the same claim as every bit failing everywhere. There are now three distinct verdicts:
| What failed | What it says |
|---|---|
| 1 byte, one bit | LIKELY U21 — names the chip |
| 1 byte, all eight bits | 1 BYTE, ALL 8 BITS - NOT A CHIP. |
| many bytes, all eight bits | ALL 8 BITS BAD - NOT ONE CHIP. SEE PLA |
One byte is a glitch, not a chip and not the PLA — those fail across the array, not at a single address. Let the burn-in decide: a fault that never returns was a one-off; one that comes back to the same address is real.
NMI was never masked
SEI does not mask NMI, CIA2 drives the NMI line, and DRAMscope starts CIA2's timers free-running for the border flash — while $DD0D had never been written. ⚠ During the march the machine is in all-RAM mode, so the NMI vector at $FFFA is memory under test. An NMI there vectors through a march pattern into garbage and executes it, and a single corrupted byte is exactly the damage that survives.
Both CIA interrupt-control registers are now cleared at entry.
⚠ RESTORE still bypasses this and always will — it is wired straight to the CPU's NMI line, not through CIA2. Do not press RESTORE while a test is running.
Download
| File | What it is |
|---|---|
| dramscope.crt | The tool. |
| READ-ME-FIRST.txt | Every colour, every mark on the map, what to do with a fault. |
| CHIP-CHART.pdf | Print this. Which chip carries which bit, all five assemblies. |
| CHIP-CHART.txt | The same chart as plain text. |
| g1probe.crt | Will it run on your cartridge? Sweeps $DE02 and reports. |
⚠ Set it up before you need it
Both devices boot straight into the cartridge with no menu — and both must be told to, on a machine that still works. Ultimate II+: Copy to Flash. Kung Fu Flash: it boots the last cartridge you selected. Either way the menu is a C64 program and needs working RAM.
No warranty; see LICENSE.
