Over time, IMSAI engineering makes changes to parts, assemblies, and products. These changes are captured in ECN or ECO documents. IMSAI has used the ECN and ECO to mean essentially the same thin. The transition from ECN to ECO happened in 1977. The format of the ECN/ECO number is ECO yy-ssss where yy is the two-digit year and ssss is a four-digit sequence number that resets to 0001 at the beginning of each year.

The table below records all known IMSAI ECN and ECO documents in chronolgical order. The numbers starting with ECO 24-0001 are all included and up to date. Previous documents will be included as they are discovered and processed.

Number	Affected	Summary
ECO 77-0035	CP-A Rev-4	Modification to cause the front panel to always come up in stop mode at power-up time.
ECO 24-0001	CP-A Rev-4	Component substitutions due to obsolescence.
ECO 24-0002	MPU-A Rev-4	Component substitutions due to obsolescence.
ECO 24-0003	PIO 4 Rev-2	Component substitutions due to obsolescence.
ECO 24-0004	PIC-8 Rev-3	Component substitutions due to obsolescence.
ECO 24-0005	SIO 2 Rev-3	Component substitutions due to obsolescence.
ECO 24-0006	SIOC Rev-2	Component substitutions due to obsolescence.
ECO 24-0007	MIO Rev-2	Component substitutions due to obsolescence.
ECO 24-0008	CP-A Rev-4	Component substitution to improve customer assembly experience.
ECO 24-0009	26-1500001; 26-1500002; 26-1500003; 26-1500004	Component substitutions due to obsolescence.
ECO 24-0010	CP-A Rev-4	LED spacers are now used to set the proper height of the LEDs from the PCB.