PM3350-SW datasheet(149/224 Pages) PMC

149 / 224 page

ELAN 8X10

PM3350 ELAN 8 X10

DATA SHEET

PMC-970109

ISSUE 3

8 PORT ETHERNET SWITCH

PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND PMC-SIERRA, INC. CUSTOMERS ONLY

147

The PCI data transfer rate is therefore:

{2*num_pm3351 * 1 (Mlp) * 1 (Mports) * 1 (Mrfr) * 1 (Mdplx) * 0.125 bits/ns (max

Mpfsz) * 1 (Mdest for unicast)} + {3*num_pm3350 * 1 (Mlp) * 8 (Mports) * 1 (Mrfr)

* 0.5 (Mdplx) * 0.0125 bits/ns (max Mpfsz) * 1 (Mdest for unicast)}

= (0.25 bits/ns + 0.20 bits/ns)

= 450 Mbit/sec

Since this number is less than 500 Mbit/sec the switch configuration will be non-

blocking.

EXAMPLE #2:

Lets examine the maximum sustainable broadcast frame for a 2 port -100 Mb, 24-port

10 Mb switch constructed using two PM3351 and three PM3350 chips assuming:

•

the 100 Mbit ports are full-duplex and the 10 Mbit ports are half-duplex

PCI bus max transfer rate is 500 Mbit/sec

< {2*num_pm3351 * 1 (Mlp) * 1 (Mports) * 1 (Mrfr_max_learn) * 1 (Mdplx) * 0.125

bits/ns (max Mpfsz) * 3 (Mdest since three other chips in the system)} +

{2*num_pm3350 * 1 (Mlp) * 8 (Mports) * 1 (Mrfr_max_learn) * 0.5 (Mdplx) *

0.0125 bits/ns (max Mpfsz) * 3 (Mdest since three other chips in the system)}

< Mrfr_max_learn * {750 Mbit/sec (received on 100 Mbit links) + 300 Mbit/sec

(received on 10 Mbit link)}

Solving for Mrfr_max_learn gives:

Mrfr_max_learn = 500 Mbit/s / (1050 Mbit/s) = 0.47

So the PCI expansion bus has a transfer rate adequate to support up to 47% of the

frames received being “broadcast to all chips in the system” (this could include frames

that are required to be learned).

EXAMPLE #3:

Determine an equation that gives the maximum number of 100 Mbit and 10 Mbit ports

that can be used with the PM3351 and PM3350 devices and still allows for a non-

blocking switch implementation. Given:

•

all destination traffic is unicast

PM3350-SW Datasheet(PDF) 149 Page - PMC-Sierra, Inc