IDT79R4700-100G IDT, Integrated Device Technology Inc, IDT79R4700-100G Datasheet - Page 6

• Manufacturer Part Number: IDT79R4700-100G
• Description: IC MPU 64BIT 5V 100MHZ 179-PGA
• Manufacturer: IDT, Integrated Device Technology Inc

Specifications of IDT79R4700-100G

• Processor Type: RISC 64-Bit
• Speed: 100MHz
• Voltage: 5V
• Mounting Type: Surface Mount
• Package / Case: 179-PGA
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Other names: 79R4700-100G

address translation occurs in parallel with the cache access, further
increasing performance by allowing these two operations to occur simul-
taneously. The tag holds a 24-bit physical address and valid bit and is
parity protected.
in a single processor cycle. For a peak instruction bandwidth of 800MB/
sec at 200MHz, instruction fetches require only 32 bits per cycle. To
reduce power dissipation, sequential accesses take advantage of the
64-bit fetch. To minimize the cache miss penalty, cache miss refill writes
use 64 bits-per-cycle, and to maximize cache performance, the line size
is eight instructions (32 bytes).
Data Cache
chip data cache that is two-way set associative with a fixed 32-byte
(eight words) line size.
with a single parity bit. It is virtually indexed and physically tagged to
allow simultaneous address translation and data cache access
cache line does not immediately cause memory to be updated. This
increases system performance by reducing bus traffic and eliminating
the bottleneck of waiting for each store operation to finish before issuing
a subsequent memory operation. Software can however select write-
through on a per-page basis when it is appropriate, such as for frame
buffers.
executes a Store instruction, this single-entry buffer gets written with the
store data while the tag comparison is performed. If the tag matches,
then the data is written into the data cache in the next cycle that the data
cache is not accessed (the next non-load cycle). The store buffer allows
the R4700 to execute a store instruction every processor cycle and to
perform back-to-back stores without penalty.
bandwidth of 1.6 GB/sec.
Write Buffer
backs, stores to uncached or write-through addresses—use the on-chip
write buffer. The write buffer holds a maximum of four 64-bit address and
64-bit data pairs. The entire buffer is used for a data cache writeback
and allows the processor to proceed in parallel with memory updates.
System Interface
ates from two clocks—TClock[1:0] and RClock[1:0]—provided by the
RC4700, at some division of the internal clock.
IDT79R4700
Because the cache is virtually indexed, the virtual-to-physical
The instruction cache is 64-bits wide and can be refilled or accessed
For fast, single cycle data access, the RC4700 includes a 16KB on-
The data cache is protected with byte parity and its tag is protected
The normal write policy is writeback, which means that a store to a
Associated with the data cache is the store buffer. When the RC4700
The data cache can provide 8 bytes each clock cycle, for a peak
Writes to external memory—whether they are cache miss write-
The RC4700 supports a 64-bit system interface. This interface oper-
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eight check bits and a 9-bit command bus protected with parity. In addi-
tion, there are eight handshake signals and six interrupt inputs. The
interface has a simple timing specification and is capable of transferring
data between the processor and memory at a peak rate of 500MB/sec
with a 67MHz bus.
System Address/Data Bus
addresses and data between the RC4700 and the rest of the system. It
is protected with an 8-bit parity check bus, SysADC.
memory and I/O systems of varying frequencies. The data rate and the
bus frequency at which the RC4700 transmits data to the system inter-
face are programmable via boot time mode control bits. Also, the rate at
which the processor receives data is fully controlled by the external
device. Therefore, either a low cost interface requiring no read or write
buffering or a faster, high performance interface can be designed to
communicate with the RC4700. Again, the system designer has the flex-
ibility to make these price/performance trade-offs.
System Command Bus
The command bus indicates whether the SysAD bus carries an address
or data. If the SysAD carries an address, then the SysCmd bus also
indicates what type of transaction is to take place (for example, a read
or write). If the SysAD carries data, then the SysCmd bus also gives
information about the data (for example, this is the last data word trans-
mitted, or the cache state of this data line is clean exclusive). The
SysCmd bus is bidirectional to support both processor requests and
external requests to the RC4700. Processor requests are initiated by
the RC4700 and responded to by an external device. External requests
are issued by an external device and require the RC4700 to respond.
SysAD bus. In the case of a sub-doubleword transfer, the low-order
three address bits give the byte address of the transfer, and the
SysCmd bus indicates the number of bytes being transferred.
Handshake Signals
these, RdRdy* and WrRdy* are used by an external device to indicate to
the RC4700 whether it can accept a new read or write transaction. The
RC4700 samples these signals before deasserting the address on read
and write requests.
SysCmd buses between the processor and an external device. When
an external device needs to control the interface, it asserts ExtRqst*.
The RC4700 responds by asserting Release* to release the system
interface to slave state.
The system interface consists of a 64-bit Address/Data bus with
The 64-bit System Address Data (SysAD) bus is used to transfer
The system interface is configurable to allow easier interfacing to
The RC4700 interface has a 9-bit System Command (SysCmd) bus.
The RC4700 supports one to eight byte and block transfers on the
There are six handshake signals on the system interface. Two of
ExtRqst* and Release* are used to transfer control of the SysAD and
December 5, 2008