HIMA HIMax, System Manual

Page: 31 / 122

HIMax System 3 Product Description
HI 801 001 E Rev. 4.01 Page 31 of 122
In this example, the following values are assumed for calculating the maximum system bus
latency:
t
Switch
Internal switch latency 5 µs
c Light velocity 300 000 km/s
Damping
Fiber optic cable
Fiber optic cable damping 2 is assumed
Damping
Cu
Copper cable damping 2 is assumed
l
Cu
Length of the copper cable,
identical for all cables 100 m
l
Fiber Optic Cable
Length of the fiber optic cable,
identical for all cables 10 km
t
Fiber Optic Cable
Runtime over 10 km fiber optic
cable =l
Fiber Optic Cable
*Damping
Fiber Optic Cable
/c
= 66.7 µs
t
Cu
Runtime over 100 m copper
cable =l
Cu
*Damping
Cu
/c = 0.667 µs
t
Rack
Latency per rack with I/O mod-
ules 65 µs
t
Message
Message running time at
1 GBit/s, considered one time
for each segment 6.592 µs
The latency is calculated for the following connections:
ƒ Connection between rack 3 and rack 0. With respect to the type and number of the
network components; this corresponds to the connections between rack 6, 9 or 12 and
rack 0.
ƒ Connection between rack 15 and rack 0. With respect to the type and number of the
network components; this corresponds to the connections between rack 13 or 14 and
rack 0.
The connection to the remaining racks have less network components and therefore a
lower latency.
Calculation of the latency t
Latency
between rack 3 and rack 0:
t
Latency
= 4*t
Cu
+ t
Switch
+ (n
Racks
-1)*t
Rack
+ 4*t
Message
= 4*0.667 µs + 5 µs + 15*65 µs +
4*6.592 µs= 2.667 µs + 5 µs + 975 µs + 26.368 µs = 1009.036 µs
Explanation:
4*t
Cu
4 copper cables between racks 3, 2, 1, switch A and rack 0
n
Racks
Number of base plates, here 16
(n
Racks
-1)*t
Rack
Latency for the following base plates:
ƒ Rack 3 itself
ƒ 11 additional racks (1, 2, 4…12) connected to switch A
ƒ One rack (13) connected to switch B
ƒ Two racks (14 and 15) connected to switch C
Calculation of the latency t
Latency
between rack 15 and rack 0:
t
Latency
= 2*t
Cu
+ 2*t
Switch
+ t
Fiber Optic Cable
+ (n
Racks
-1)*t
Rack
+ 3*t
Message
= 2*0.667 µs + 2*5 µs +
66.7 µs + 15*65 µs + 3*6.592 µs= 1072.81 µs