 96 pin MALE or FEMALE (Fujitsu FCN 234P096-G/Y) connector at the motherboard | It was introduced in 1989 to be a high-speed bus counterpart to their high-speed SPARC processors, replacing the earlier (and by this time, outdated) VMEbus that had been used in their earlier Motorola 68030-based systems and early SPARC boxes. When Sun was attempting to "open" the SPARC in the early 1990s, SBus was likewise standardized and became IEEE-1496. In 1997 Sun started to migrate away from SBus onto PCI, and today SBus is no longer used.
SBus is in many ways a "clean" design. It was targeted only to the SPARC so many cross-platform issues were simply not a consideration. SBus was based on a big-endian 32-bit address and data bus, run at 25MHz and thus transfers up to 100Mbyte/second. Devices are each mapped onto a 28-bit address space (16 megabytes), and only eight masters are supported although there are an unlimited number of slaves.
When the 64-bit UltraSPARC was introduced SBus was modified to use clock-doubling and transfer two 32-bit data words per cycle to produce a 200MByte/s 64-bit bus. For contrast, modern 66MHz/64-bit PCI is 528MByte/s.
SBus was a peripheral interconnect only (like PCI). Sun systems used another standardized system as a CPU-memory bus, MBus.
| Pin |
Name |
Description |
| 1 |
GND |
Ground |
| 2 |
sb_br* |
sb_br |
| 3 |
sb_sel* |
sb_sel |
| 4 |
sb_irql* |
? |
| 5 |
sb_d(0) |
Data bit 0 |
| 6 |
sb_d(2) |
Data bit 2 |
| 7 |
sb_d(4) |
Data bit 4 |
| 8 |
sb_irq2* |
Interrupt Request 2 |
| 9 |
sb_d(6) |
Data bit 6 |
| 10 |
sb_d(8) |
Data bit 8 |
| 11 |
sb_d(10) |
Data bit 10 |
| 12 |
sb_irq3* |
Interrupt Request 3 |
| 13 |
sb_d(12) |
Data bit 12 |
| 14 |
sb_d(14) |
Data bit 14 |
| 15 |
sb_d(16) |
Data bit 16 |
| 16 |
sb_irq4* |
Interrupt Request 4 |
| 17 |
sb_d(19) |
Data bit 19 |
| 18 |
sb_d(21) |
Data bit 21 |
| 19 |
sb_d(23) |
Data bit 23 |
| 20 |
sb_irq5* |
Interrupt Request 5 |
| 21 |
sb_d(25) |
Data bit 25 |
| 22 |
sb_d(27) |
Data bit 27 |
| 23 |
sb_d(29) |
Data bit 29 |
| 24 |
sb_irq6* |
Interrupt Request 6 |
| 25 |
sb_d(31) |
Data bit 31 |
| 26 |
sb_siz(0) |
sb_siz(0 |
| 27 |
sb_siz(2) |
sb_siz(2 |
| 28 |
sb_irq7* |
Interrupt Request 7 |
| 29 |
sb_a(0) |
Address bit 0 |
| 30 |
sb_a(2) |
Address bit 2 |
| 31 |
sb_a(4) |
Address bit 4 |
| 32 |
sb_merr* |
sb_merr |
| 33 |
sb_a(6) |
Address bit 6 |
| 34 |
sb_a(8) |
Address bit 8 |
| 35 |
sb_a(10) |
Address bit 10 |
| 36 |
sb_err* |
sb_err |
| 37 |
sb_pa(12) |
Address bit 12 |
| 38 |
sb_pa(14) |
Address bit 14 |
| 39 |
sb_pa(16) |
Address bit 16 |
| 40 |
sb_ack8* |
sb_ack8 |
| 41 |
sb_pa(18) |
Address bit 18 |
| 42 |
sb_pa(20) |
Address bit 20 |
| 43 |
sb_pa(22) |
Address bit 22 |
| 44 |
sb_ack32* |
sb_ack32 |
| 45 |
sb_pa(24) |
Address bit 24 |
| 46 |
sb_pa(26) |
Address bit 26 |
| 47 |
N/C |
Not connected |
| 48 |
-12V |
-12 VDC |
| 49 |
sb_clk |
Clock |
| 50 |
sb_bg* |
sb_bg |
| 51 |
sb_as* |
sb_as |
| 52 |
GND |
Ground |
| 53 |
sb_d(1) |
Data bit 1 |
| 54 |
sb_d(3) |
Data bit 3 |
| 55 |
sb_d(5) |
Data bit 5 |
| 56 |
+5V |
+5 VDC |
| 57 |
sb_d(7) |
Data bit 7 |
| 58 |
sb_d(9) |
Data bit 9 |
| 59 |
sb_d(11) |
Data bit 11 |
| 60 |
GND |
Ground |
| 61 |
sb_d(13) |
Data bit 13 |
| 62 |
sb_d(15) |
Data bit 15 |
| 63 |
sb_d(17) |
Data bit 17 |
| 64 |
+5V |
+5 VDC |
| 65 |
sb_d(18) |
Data bit 18 |
| 66 |
sb_d(20) |
Data bit 20 |
| 67 |
sb_d(22) |
Data bit 22 |
| 68 |
GND |
Ground |
| 69 |
sb_d(24) |
Data bit 24 |
| 70 |
sb_d(26) |
Data bit 26 |
| 71 |
sb_d(28) |
Data bit 28 |
| 72 |
+5V |
+5 VDC |
| 73 |
sb_d(30) |
Data bit 30 |
| 74 |
sb_siz(1) |
sb_siz(1 |
| 75 |
sb_rd |
sb_rd |
| 76 |
GND |
Ground |
| 77 |
sb_a(1) |
Address bit 1 |
| 78 |
sb_a(3) |
Address bit 3 |
| 79 |
sb_a(5) |
Address bit 5 |
| 80 |
+5V |
+5 VDC |
| 81 |
sb_a(7) |
Address bit 7 |
| 82 |
sb_a(9) |
Address bit 9 |
| 83 |
sb_a(11) |
Address bit 11 |
| 84 |
GND |
Ground |
| 85 |
sb_pa(13) |
Address bit 13 |
| 86 |
sb_pa(15) |
Address bit 15 |
| 87 |
sb_pa(17) |
Address bit 17 |
| 88 |
+5V |
+5 VDC |
| 89 |
sb_pa(19) |
Address bit 19 |
| 90 |
sb_pa(21) |
Address bit 21 |
| 91 |
sb_pa(23) |
Address bit 23 |
| 92 |
GND |
Ground |
| 93 |
sb_pa(25) |
Address bit 25 |
| 94 |
sb_pa(27) |
Address bit 27 |
| 95 |
sb_reset* |
Reset |
| 96 |
+12V |
+12 VDC |
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