10 of 47

March 31, 2008

IDT80KSW0004

Datasheet

Switch Latency in “Store-and-Forward” mode

Table 5 Switch Latency Table (Store-and-Forward mode)

1) Values are guaranteed by characterization, but are not production tested.

2) For those specifications associated with an sRIO transaction, it should be noted that the upper limit to a specification may be dictated by sRIO

priority handling. For example, a maintenance read packet having lower priority may be held off until higher priority packets in queue are serviced.

The user should take into consideration this additional priority-induced delay when examining these specifications. I2C and JTAG transactions are

always deterministic and follow these specifications identically.

3) Switch latency is a statistical function, which typically increases with increased traffic loading on the switch. Values shown in Table 5 are for

single input port to single output port with matching input and output port rates in “Store-and-Forward” mode, no other switch loading. The switch

latency in “Store-and-Forward” packet forward methodology is also a strong function of port rate. For specific values under other specific applica-

tion usage scenarios and traffic conditions, please contact IDT technical support.

Switch Latency in “Cut-Through” mode

Table 6 Switch Latency Table (Cut-Through mode)

1) Values shown in Table 6 are typical for single input port to single output port with matching input and output port rates in “Cut-Through” mode,

no other switch loading. For specific values under other specific application usage scenarios and traffic conditions, please contact IDT technical

support.

Note:

In "Store-and-Forward" mode and "Cut-Through" mode when trace and filter are enabled at the same time, the latency for packets sent to the

trace port will increase by the time taken to send 20 bytes into the port ([20 bytes * 8 ] * 1/[port_speed * 0.8]). The latency for other traffic flow will

be unaffected.

Pay Load Size

1.25GHz

2.5GHz

3.125GHz

1X

4X

1X

4X

1X

4X

8 Byte

456 ns

343 ns

277 ns

225 ns

246 ns

209 ns

16 Byte

517 ns

360 ns

311 ns

231 ns

267 ns

213 ns

32 Byte

652 ns

435 ns

375 ns

272 ns

320 ns

239 ns

64 Byte

902 ns

500 ns

501 ns

305 ns

422 ns

263 ns

128 Byte

1425 ns

722 ns

757 ns

417 ns

630 ns

352 ns

256 Byte

2451 ns

1071 ns

1273 ns

590 ns

1035 ns

492 ns

Multicast Event

Control Symbol

115 ns

105 ns

60 ns

55 ns

50 ns

45 ns

Pay Load Size

1.25GHz

2.5GHz

3.125GHz

1X

4X

1X

4X

1X

4X

8 Byte

366 ns

322 ns

244 ns

216 ns

208 ns

199 ns

16 Byte

363 ns

324 ns

234 ns

215 ns

206 ns

197 ns

32 Byte

365 ns

316 ns

232 ns

215 ns

205 ns

198 ns

64 Byte

365 ns

318 ns

234 ns

219 ns

204 ns

198 ns

128 Byte

372 ns

314 ns

233 ns

217 ns

210 ns

196 ns

256 Byte

371 ns

312 ns

238 ns

216 ns

205 ns

195 ns