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Comment by phendrenad2 | Hacker News Reader

Fun fact: Very early Macintoshes were quite hackable, and plans for hacks like this were frequently done. There was even a kit someone made that added SCSI to the original Macintosh (basically duplicating circuitry from the Macintosh SE). That kit required soldering wires directly onto the CPU pins.

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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 (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.

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.

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.

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.

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

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.

I think as well about people who created accelerator boards, and recreated the functions of the logic board at various levels of sophistication. There are (I think) 68030 upgrades to the original Macintosh Plus, for example, that add RAM way beyond the wildest dreams of any owner back then.

I think the greatest achievement here was was the Radius Rocket Stage II, which was essentially an entire logic board on a NuBus card that claimed to System 7 to be a Quadra 950, but was essentially a diskless, portless Mac that could be run independently of the host system!

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