SCI Basics Hugo Kohmann SCI Basics Slide 1

What is SCI Ø The SCI standard ANSI/IEEE 1596 -1992 defines a point-to-point interface and a set of packet protocols. Ø The SCI protocols use small packet sizes with a 16 -byte header and data sizes of 16, 64, (128) and {256} bytes. Each packet is protected by a 16 -bit CRC code. An SCI interface has two unidirectional links that operate concurrently. Ø The SCI protocols support shared memory by encapsulating bus requests and responses into SCI request and response packets. Packet-based handshake protocols guarantee reliable data delivery. Ø SCI use 64 bits addressing and the most significant 16 bits are used for addressing up to 64 K nodes. Ø A set of cache coherence protocols are defined to maintain cache coherence in a shared memory system. Ø Message passing is supported by a compatible subset of the SCI protocols. This protocol subset does not invoke SCI cache coherency protocols. SCI Basics Slide 2

Dolphins realization - The Node. Chip - LC family q Ga. As Node. Chip Ø Dolphins first realization of SCI, 1993 Ø 500 MB/s Link Speed Ø Technology Licensed to Convex/Vitesse q CMOS Node. Chip Ø Low Cost version, 1993 Ø 125 MB/s Link Speed q LC 1 Ø Available since 1995 Ø 200 MB/s Link Speed q LC 2 Ø Available since 1996 Ø 500 MB/s Link Speed q LC 3 Ø Prototype in May 2000, Volumes in August 2000 SCI Basics Slide 3

LC 3 Overveiew q ANSI/IEEE Std 1596 -1992 Compliant Ø LVDS Link Interface q ANSI/IEEE Std 1159. 1 JTAG support q 272 Plastic BGA, Max 2 Watt q Worst case timing 166 MHz. Tested at 250 Mhz q 16 Internal buffers (8 Input / 8 Output ) q Virtual channels enables in order SCI packet delivery q Two wire serial line interface for configuration and management q Hardware Initialization Ø Automatic scrubber selection Ø Initial nodeid assignment q Performance Counters Ø Will count packets received, bypassed, transmitted, etc. Ø Masked compare of command symbol SCI Basics Slide 4

Overview (cont. ) q B-Link. TM and Bx. Bar. TM Cross. Bar interface Ø Low Signal Count Ø Embedded SCI Packets (multiplexed address/data) Ø High Performance Ø Compliant with SCI Ø Enables Pipelining (multiple outstanding transactions) Ø B-Link 100 MHz, 64 bit Shared bus Ø Bx. Bar 100 MHz, 2 x 32 Bit Crossbar Interface SCI Basics Slide 5

Link. Controller-3 Overview CLOCK FRAME B-Link Bx. Bar Time DATA HERE B-Link Data Format code tgt. . . Embedded SCI Packet crc BUSY post resrv parity I 2 C/EPROM/PLD LC-3 CLK 18 18 FLAG DATA (16) SCI out SCI in tgt cmd src cnt addr/data crc R/W 0, 16, 64, 128 bytes Lock Coherent. . . Time SCI Basics Slide 6

LC-3 APPLICATION EXAMPLE Node CPU CPU Mem Node CPU SCI Controller LC-3 CPU Mem SCI Controller LC-3 SCI FABRIC SWITCH I/O Expansion LC-3 SCI Basics LC-3 PCI Disk Subsystem SCI SYSTEM Slide 7

LC Simplified Block Diagram B-Link Clock Domain B-Link control input queue 4 entry B-Link Packet Asm CSR control queue control routing lookup RAM output queue 4 entry IEEE init CRC calc deskew RAM based bypass FIFO routing lookup RAM echo CAM Upstream Clock Domain SCI Basics output control idle generator 34 compress 34 parser 18 expand CRC calc 18 init control Downstream Clock Domain Slide 8

Sample Packet Traversal Req, trid 0 input queue output queue echo CAM Req, trid 1 input queue output queue input queue echo CAM bypass FIFO output queue echo CAM bypass FIFO done echo bypass FIFO echo CAM input queue bypass FIFO echo CAM output queue input queue output queue SCI Basics Slide 9

Sample Packet Traversal (cont. ) input queue output queue echo CAM input queue output queue bypass FIFO done echo bypass FIFO echo CAM input queue busy echo bypass FIFO echo CAM output queue input queue output queue SCI Basics output queue echo CAM bypass FIFO input queue Slide 10

Sample Packet Traversal (cont. ) input queue output queue echo CAM bypass FIFO echo CAM input queue output queue SCI Basics Slide 11

PSB 66 q 64 bit / 66 MHz PCI Bridge Ø 313 BGA - Power consumption : 3 Watt Ø PCI 2. 1 Compliant Ø Smart Chained DMA w DMA barrier operation w Complete or stop Ø Performance enhancements w > 300 MB/s w 128 Byte SCI packets ( short 256 ) w Enhanced Internal Logic Ø Samples available now Ø Volumes from December 2000 SCI Basics Slide 12

Application Examples PCI-SCI Adapter card LC-3 PSB Low Cost 4 -way Switch High Performance 8 -way Scaleable Switch Bx. Bar Crossbar LC-2 SCI Basics LC-2 LC-3 LC-3 Slide 13