The Jt9d was a 'part throttle' engine. It would give you what ever you required in the way of thrust, up until the 'speeder spring' in the JFC limited the RPM.
The RB211-22 up to the RB211-524d the fuel control amplifier limited thrust.(N1 and N2)
As 411A states some operators had the EGT channel whilst others, BA for one had it isolated. However if the amp was switched out the only limit came from the FFR, hence the requirement to throttle back before switching the amplifier to override.
The Trent series of Rollers do not detect a TGT exceedance
B777 the EGT EICAS figure turns red for an exceedance and returns to white as the overtemp comes back into limits. However the EGT 'box' remains red until the exceedance page is erased.The exceedance page gives a timeline of temperature and time above.