Comparison of modern relay computers

	A fistful of relays	Harry Porter's	Relay computer two	RC-3	Simon	Zusie	TIM	DUO 14 Premium	Relay computer "trainer"	i² 8-Bit Relay Computer	Kilian Leonhardt's	Der Relaisrechner	MERCIA
Component	Used number of relays
ALU	92	58	50	64	.	.	12	.	.	.	.	.	224
Registers	97	126	55	106	.	.	.	.	.	.	.	.	.
PC unit	28	108	80	104	.	.	.	.	.	.	.	.	.
Sequencer	30	35	16	44	.	.	.	.	.	.	.	.	.
Instruction decoder	46	50	60	48	.	.	.	.	.	.	.	.	.
Memory unit	25(*)	37	20	44	.	.	.	.	.	.	.	.	.
Total	303 4PDT	415 4PDT	281	418 4PDT	80	.	152	55	83	~300	1500	.	1950 SPDT
	Registers
Data storage	7 8-bit (*)	8 8-bit	3 8-bit	8 8-bit	12 2-bit	3 8-bit	5 8-bit	.	.	3 8-bit	.	8 8-bit	5 10-bit
ALU input/output	8 8-bit (*)	4 8-bit	3 8-bit	4 8-bit	6 2-bit	3 8-bit	.	.	.	2 8-bit	.	8 8-bit	3 10-bit
Memory pointer	3 8-bit (*)	1 16-bit
-	2 12-bit	.	.	.	.	.	8 8-bit
Other registers	8-bit PC	1 16-bit	.	1 16-bit	11 2-bit	1 12-bit	.	3-bit PC	8-bit PC, 1-bit carry, 4-bit output	.	.	12-bit PC	10-bit PC, return, jump
Total	8 8-bit (*)	8 8-bit	3 8-bit	8 8-bit	15 2-bit	3 8-bit, 3 12-bit	5 8-bit	.	3	3 8-bit	16 11-bit	8 8-bit, 12-bit PC, 8-bit shadow ALU output	8 10-bit
Shadow registers	1 8-bit	1 16-bit	1 16-bit	1 16-bit	2 2-bit	.	.	.	.	.	.	1 8-bit ALU output	1 10-bit
	Instructions
Instruction width, bits	16(*)	8-24	.	8-24	.	.	.	6	32	8/16	18	16	10
Total	21(*)	19	15	23	9	34	16	3	31	15	13	??	29 available, 21 used
	Memory
Address bus width	8 program/data (*)	16 program/data	16 program/data	16 program/data	-	16 program/data	4 data (12 bytes of memory on capacitors) + 4 program (16 bytes on dip switches)	3 program + 2 data	8 program + 8 data	8 program + 8 data	11 program	12 program, 9 data, 8 IO	10 program/data
Installed memory	.	.	.	.	.	.	.	.	.	.	.	.	496 bytes ROM, 512 bytes RAM
	Peripheral devices

(*) projected

PC unit includes PC register, PC incrementer, jump register, instruction register.