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It is worth mentioning that hacking those machines is much more accessible today than it was 30 years ago. While Adrian's modification was mostly period correct

by II2II 3y ago

It is worth mentioning that hacking those machines is much more accessible today than it was 30 years ago. While Adrian's modification was mostly period correct (down to the schematics that he was using), he stumbled across an error in the schematics that he was able to verify with a modern oscilloscope. While equipment with similar specifications would have existed back in the day, it wouldn't have been affordable to a hobbiest (even a semi-professional one) working from their basement. Old electronics is fun simply because what was once cutting edge is now available to a wider audience.

gorkish 3y ago
He only used the scope to look for activity on the pins; he did not really rely on any of its "modern" features. His mod was well within the capabilities of the home hobbyist at the time. Swapping DRAM chips around was a well trodden path. I think it's probably more important to note that a 4MB SIMM would have run close to $200 at the time this was all current hardware.
- bombcar 3y ago
  Or almost $500 today The tolerances of the various components was larger back then, allowing weird things like this to work without expensive precision tools. High tolerances also allowed things like "hot plugging expansion cards" to get past various limitations.
- II2II 3y ago
  Perhaps there were other ways to see whether there was activity on the bus, but I was thinking of having a scope that was useful for the 8 MHz bus speed. Yes, they existed. On the other hand, they were not affordable for most people. And yes, memory was expensive back then. I remember spending several hundred dollars to get 16 MB in 1992. That purchasing decision biases my computer purchases to this day. I still over provision RAM after reaping the benefits of it over 30 years ago.
  - bogantech 3y ago
    Back in those days you'd check for activity using a logic probe, cheap and simple. People don't use those much any more because we're spoilt with our cheap scopes
  - gorkish 3y ago
    There are a number of ways to probe a data bus for the presence of a signal. You don't need a scope capable of fully characterizing it to know it's there. And furthermore it wasn't difficult or expensive to get ahold of a 10 year old scope in the 90's; it just took slightly more effort.

by II2II 3y ago

gorkish 3y ago

He only used the scope to look for activity on the pins; he did not really rely on any of its "modern" features. His mod was well within the capabilities of the home hobbyist at the time. Swapping DRAM chips around was a well trodden path. I think it's probably more important to note that a 4MB SIMM would have run close to $200 at the time this was all current hardware.

bombcar 3y ago
Or almost $500 today The tolerances of the various components was larger back then, allowing weird things like this to work without expensive precision tools. High tolerances also allowed things like "hot plugging expansion cards" to get past various limitations.
II2II 3y ago
Perhaps there were other ways to see whether there was activity on the bus, but I was thinking of having a scope that was useful for the 8 MHz bus speed. Yes, they existed. On the other hand, they were not affordable for most people. And yes, memory was expensive back then. I remember spending several hundred dollars to get 16 MB in 1992. That purchasing decision biases my computer purchases to this day. I still over provision RAM after reaping the benefits of it over 30 years ago.
- bogantech 3y ago
  Back in those days you'd check for activity using a logic probe, cheap and simple. People don't use those much any more because we're spoilt with our cheap scopes
- gorkish 3y ago
  There are a number of ways to probe a data bus for the presence of a signal. You don't need a scope capable of fully characterizing it to know it's there. And furthermore it wasn't difficult or expensive to get ahold of a 10 year old scope in the 90's; it just took slightly more effort.