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Figure 1 – The Virtex-4 FPGA offers breakthrough DSP performance at new low-cost points.
Even more revolutionary, Virtex-4 system
designers need not employ the largest
family member to achieve this performance,
as has previously been the case.
Virtex-4 FPGAs now deliver this signal
processing capability in a medium-density
device, providing you with as much as a
staggering 10X increase in the available
GMACs per dollar (see Figure 1). This dramatically
extends production volumes
where it makes economic sense to use an
FPGA for performance-centric signal processing
applications. The new DSP slices
also dramatically reduce power consumption,
allowing you to drive down both cost
and power per channel.
DSP to Logic Resources
At the heart of the Virtex-4 FPGA’s signal
processing resources are new highly integrated
XtremeDSP slices, sometimes
referred to as DSP48s (Figure 2).
Depending on the family member, you
can utilize as many as 512 XtremeDSP
slices, each capable of providing 500 MHz
throughput.
Each slice contains a dedicated 2’s complement
signed, 18 x 18 bit multiplier, and
a three-input adder/subtracter with feedback
for accumulation modes. The addition
of a seven-bit op mode multiplexer
allows you to dynamically configure the
XtremeDSP slice for one of more than 40
operating modes, such as addition, multi-
plication, accumulation, MACC functions,
MACC cascading, wide (48-bit)
addition, and wide multiplexing.
Configuration wizards in Xilinx ISE or
System Generator for DSP allow you to
simply apply the desired function.
The addition of new XtremeDSP slices
allows you to implement many such functions
within the slice and without the need
High Performance
– 500 MHz, fully pipelined
High Integration
– 40+ DSP/arithmetic operation modes
– Directly cascadeable
Easy to implement
– Software configuration wizards
A (18-bit)
B (18-bit)
for external logic slices, which can thus be
allocated to other tasks. XtremeDSP slices
can also be cascaded directly without
accessing logic fabric or any loss in speed.
Xilinx’s new ASMBL architecture
enables us to alter the mix of XtremeDSP
slices and logic slices. The SX platform
with in the Virtex-4 family offers the
highest ratio of XtremeDSP slices to logic
slices at one XtremeDSP slice for every
108 logic slices. The SX platform is ideally
suited for multiplier or MAC-intensive
tasks such as software radios. The LX platform
offers the highest ratio of logic to
other features, and is suited for many traditional
FPFA applications that may also
require some DSP capability.
Reduced Power Consumption
In today’s infrastructure applications, driving
down cost per channel is not the only
goal diligently pursued. Wireless infrastructure
manufacturers are under increasing
pressure to stay within power limits
imposed by governing telecom standards
bodies. Power consumption is also becoming
a key concern for some military applications,
such as Joint Tactical Radio
Systems radios.
The integrated XtremeDSP slices on
Virtex-4 FPGAs eliminate the need to use
logic slices for many signal processing and
arithmetic tasks, reducing the need for
power-consuming routing resources. Initial
Winter 2004 Xcell Journal 61
C (48-bit)
Optional Pipeline Register/
Routing Logic
BCOUT PCOUT
BCIN
DIGITAL SIGNAL PROCESSING
The integrated XtremeDSP slices on Virtex-4 FPGAs minimize the need
to use logic slices for many signal processing and arithmetic tasks...
Multiplier
Optional Register
Routing Logic
Optional Pipeline Register/
Routing Logic
PCIN
Figure 2 – New XtremeDSP slices feature 18 x 18 bit multiply, 48-bit accumulator
P (48-bit)