49 research outputs found
An Energy-Efficient Reconfigurable Mobile Memory Interface for Computing Systems
The critical need for higher power efficiency and bandwidth transceiver design has significantly increased as mobile devices, such as smart phones, laptops, tablets, and ultra-portable personal digital assistants continue to be constructed using heterogeneous intellectual properties such as central processing units (CPUs), graphics processing units (GPUs), digital signal processors, dynamic random-access memories (DRAMs), sensors, and graphics/image processing units and to have enhanced graphic computing and video processing capabilities. However, the current mobile interface technologies which support CPU to memory communication (e.g. baseband-only signaling) have critical limitations, particularly super-linear energy consumption, limited bandwidth, and non-reconfigurable data access. As a consequence, there is a critical need to improve both energy efficiency and bandwidth for future mobile devices.;The primary goal of this study is to design an energy-efficient reconfigurable mobile memory interface for mobile computing systems in order to dramatically enhance the circuit and system bandwidth and power efficiency. The proposed energy efficient mobile memory interface which utilizes an advanced base-band (BB) signaling and a RF-band signaling is capable of simultaneous bi-directional communication and reconfigurable data access. It also increases power efficiency and bandwidth between mobile CPUs and memory subsystems on a single-ended shared transmission line. Moreover, due to multiple data communication on a single-ended shared transmission line, the number of transmission lines between mobile CPU and memories is considerably reduced, resulting in significant technological innovations, (e.g. more compact devices and low cost packaging to mobile communication interface) and establishing the principles and feasibility of technologies for future mobile system applications. The operation and performance of the proposed transceiver are analyzed and its circuit implementation is discussed in details. A chip prototype of the transceiver was implemented in a 65nm CMOS process technology. In the measurement, the transceiver exhibits higher aggregate data throughput and better energy efficiency compared to prior works
SWIFT: A Low-Power Network-On-Chip Implementing the Token Flow Control Router Architecture With Swing-Reduced Interconnects
A 64-bit, 8 × 8 mesh network-on-chip (NoC) is presented that uses both new architectural and circuit design techniques to improve on-chip network energy-efficiency, latency, and throughput. First, we propose token flow control, which enables bypassing of flit buffering in routers, thereby reducing buffer size and their power consumption. We also incorporate reduced-swing signaling in on-chip links and crossbars to minimize datapath interconnect energy. The 64-node NoC is experimentally validated with a 2 × 2 test chip in 90 nm, 1.2 V CMOS that incorporates traffic generators to emulate the traffic of the full network. Compared with a fully synthesized baseline 8 × 8 NoC architecture designed to meet the same peak throughput, the fabricated prototype reduces network latency by 20% under uniform random traffic, when both networks are run at their maximum operating frequencies. When operated at the same frequencies, the SWIFT NoC reduces network power by 38% and 25% at saturation and low loads, respectively
Effect of Jitter on the Settling Time of Mesochronous Clock Retiming Circuits
It is well known that timing jitter can degrade the bit error rate (BER) of
receivers that recover the clock from input data. However, timing jitter can
also result in an indefinite increase in the settling time of clock recovery
circuits, particularly in low swing mesochronous systems. Mesochronous clock
retiming circuits are required in repeaterless low swing on-chip interconnects.
We first discuss how timing jitter can result in a large increase in the
settling time of the clock recovery circuit. Next, the circuit is modelled as a
Markov chain with absorbing states. The mean time to absorption of the Markov
chain, which represents the mean settling time of the circuit, is determined.
The model is validated through behavioural simulations of the circuit, the
results of which match well with the model predictions. We consider circuits
with (i) data dependent jitter, (ii) random jitter, and (iii) combination of
both of them. We show that a mismatch between the strengths of up and down
corrections of the retiming can reduce the settling time. In particular, a 10%
mismatch can reduce the mean settling time by up to 40%. We leverage this fact
toward improving the settling time performance, and propose useful techniques
based on biased training sequences and mismatched charge pumps. We also present
a coarse+fine clock retiming circuit, which can operate in coarse first mode,
to reduce the settling time substantially. These fast settling retiming
circuits are verified with circuit simulations.Comment: 23 pages, 40 figure
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Energy efficient communication across on-chip wires in digital CMOS
For the past half century, CMOS process scaling has followed Moore's law, approximately doubling transistor density every 18 months. While locally routed wires have generally scaled with transistor size, longer wires have scaled at a slower rate and in some cases have grown larger as chip size and complexity have increased. Wires routed for non-local communication now consume a large and increasing portion of the power, thermal and area budgets in CMOS designs. Additionally, dynamic energy expended in driving locally routed wires has become comparable to that expended in logic. The goal of this research is to investigate methods of reducing the energy required for on-chip communication, primarily through the use of low-voltage swing signaling. A network-on-chip routing architecture is presented that uses complementary architectural and low-voltage swing signaling techniques to significantly improve the latency, throughput and power of an on-chip network. On-chip signaling circuits are presented that improve the suitability of low-voltage swing signaling for short wire lengths and reduced supply voltages. Finally, a procedure for improving the energy efficiency of wire loads in digital CMOS through the automated insertion of low-voltage swing signaling circuits is presented