SIB byte (32/64-bit addressing)

From Asmpedia

SIB byte - Scale (bits 6-7) Index (bits 3-5) Base (bits 0-2)

scale=00	EAX/RAX base=000	ECX/RCX base=001	EDX/RDX base=010	EBX/RBX base=011	ESP/RSP base=100	Mod* base=101	ESI/RSI base=110	EDI/RDI base=111
[EAX/RAX] index=000	00	01	02	03	04	05	06	07
[ECX/RCX] index=001	08	09	0A	0B	0C	0D	0E	0F
[EDX/RDX] index=010	10	11	12	13	14	15	16	17
[EBX/RBX] index=011	18	19	1A	1B	1C	1D	1E	1F
none index=100	20	21	22	23	24	25	26	27
[EBP/RBP] index=101	28	29	2A	2B	2C	2D	2E	2F
[ESI/RSI] index=110	30	31	32	33	34	35	36	37
[EDI/RDI] index=111	38	39	3A	3B	3C	3D	3E	3F

---

scale=01	EAX/RAX base=000	ECX/RCX base=001	EDX/RDX base=010	EBX/RBX base=011	ESP/RSP base=100	Mod* base=101	ESI/RSI base=110	EDI/RDI base=111
[EAX/RAX*2] index=000	40	41	42	43	44	45	46	47
[ECX/RCX*2] index=001	48	49	4A	4B	4C	4D	4E	4F
[EDX/RDX*2] index=010	50	51	52	53	54	55	56	57
[EBX/RBX*2] index=011	58	59	5A	5B	5C	5D	5E	5F
none index=100	60	61	62	63	64	65	66	67
[EBP/RBP*2] index=101	68	69	6A	6B	6C	6D	6E	6F
[ESI/RSI*2] index=110	70	71	72	73	74	75	76	77
[EDI/RDI*2] index=111	78	79	7A	7B	7C	7D	7E	7F

---

scale=10	EAX/RAX base=000	ECX/RCX base=001	EDX/RDX base=010	EBX/RBX base=011	ESP/RSP base=100	Mod* base=101	ESI/RSI base=110	EDI/RDI base=111
[EAX/RAX*4] index=000	80	81	82	83	84	85	86	87
[ECX/RCX*4] index=001	88	89	8A	8B	8C	8D	8E	8F
[EDX/RDX*4] index=010	90	91	92	93	94	95	96	97
[EBX/RBX*4] index=011	98	99	9A	9B	9C	9D	9E	9F
none index=100	A0	A1	A2	A3	A4	A5	A6	A7
[EBP/RBP*4] index=101	A8	A9	AA	AB	AC	AD	AE	AF
[ESI/RSI*4] index=110	B0	B1	B2	B3	B4	B5	B6	B7
[EDI/RDI*4] index=111	B8	B9	BA	BB	BC	BD	BE	BF

---

Mod*

Mod	EA (effective address)
00	[Index*Scale+disp32]
01	[EBP/RBP+Index*Scale+disp8]
10	[EBP/RBP+Index*Scale+disp32]