Was just watching on Airline Disasters how Helios 737 went unpressurized because mx left the pressure controller in MAN and neither pilot caught it on preflight. Then when they started climbing depressurized, apparently their 737s alarm for cabin altitude above 10K was the same as takeoff config alarm, so they spent the next few thousand feet troubleshooting why they were getting a takeoff config alarm. All the time becoming hypoxic and instead of descending or even leveling off, they continued climbing trying to fix a whole bunch of unbroken stuff. Then apparently their only sign the cabin 02masks had fallen was a master caution which they associated with a fault in instrument cooling. By then I'm sure hypoxia had fully set in. Finally the 737 flys to Athens, enters holding until it runs out of fuel and crashes in the hills outside Athens unpressurized the whole time.

This was in 2005 and just an EICAS system would have obviously saved this whole 737 full of pax. Obviously Boeing knew how to build EICAS since it was in the 757 from the late 70's.