| Features | 4004 | 4040 |
| Program memory | 4 KB | 8 KB (two 4 KB banks) |
| Stack memory | 3 levels | 7 levels |
| Registers | 16 index registers | 24 index registers (two banks - 16 and 8 registers) |
| Instructions | | 16 additional instructions (see below)
AND and OR logical instructions
Interrupt-related instructions
ROM and index bank selection instructions
Two new load accumulator instructions |
| Interrupts | None | Program can be interrupted by external signal |
| Pins/signals | | STP - switch processor to STOP mode
STP ACK - processor is in STOP mode
INT - interrupt input
INT ACK - interrupt acknowledge
CM-ROM1- - ROM bank selection output |
| Other features | | Single step operation |
| Package | 16-pin DIP | 24-pin DIP |
CY Pin
Is the Carry output. The state of the carry flip flop is present on this output and updated each X1 time.Output is open drain requiring pull down resistor to VDD
( Intel data book 1977 )
Another additional pin
The 4040 has another additional pin that is not present in the 4004 -- the CY pin. Unfortunately, I can't find anything saying what this pin is, though I get it is perhaps the status of the CY (carry bit) flip-flop. Does anyone know?
speed
I want to know the difference in speed please