High-Performance DRAM System Design Constraints and Considerations

The effects of a realistic memory system have not received much attention in recent decades. Often, the memory controller and DRAMs are modeled as a fixed-latency or random-latency system, which leads to simulations that are less accurate. As more cores are added to each die and CPU clock rates continue to outpace memory access times, the gap will only grow wider and simulation results will be less accurate. This thesis proposes to look at the way a memory controller and DRAM system work and attempt to model them accurately in a simulator. It will use a simulated Alpha 21264 processor in conjunction with a full system simulator and memory system simulator. Various SPEC06 benchmarks are used to look at runtimes. The process of mapping a memory location to a physical location, the algorithm for choosing the ordering of commands to be sent to the DRAMs and the method of managing the row buffers are examined in detail. We find that the choice in these algorithms and policies can affect application runtime by up to 200% or more. It is also shown that energy use can vary by up to 300% by changing changing the address mapping policy. These results show that it is important to look at all the available policies to optimize the memory system for the type of workload that a machine will be running. No single policy is best for every application, so it is important to understand the interaction of the application and the memory system to improve performance and reduce the energy consumed

Interacting Fermion Systems from Two Dimensional QCD

We consider two dimensional U(N) QCD on the cylinder with a timelike Wilson line in an arbitrary representation. We show that the theory is equivalent to N fermions with internal degrees of freedom which interact among themselves with a generalized Sutherland-type interaction. By evaluating the expectation value of the Wilson line in the original theory we explicitly find the spectrum and degeneracies of these particle systems.Comment: 11 pages, UVA-93-11, CERN-TH-6994/9

Flows and Solitary Waves in Unitary Matrix Models with Logarithmic Potentials

We investigate unitary one-matrix models coupled to bosonic quarks. We derive a flow equation for the square-root of the specific heat as a function of the renormalized quark mass. We show numerically that the flows have a finite number of solitary waves, and we postulate that their number equals the number of quark flavors. We also study the nonperturbative behavior of this theory and show that as the number of flavors diverges, the flow does not reach two-dimensional gravity.Comment: 26 pages + 4 figure

Gravitational Scattering in the c = 1 Matrix Model

The $c=1$ matrix model is equivalent to $1+1$ dimensional string theory. However, the tachyon self-interaction in the former is local, while in the latter it is nonlocal due to the gravitational, dilaton and higher string fields. By studying scattering of classical pulses we show that the appropriate nonlocal field redefinition converts the local matrix model interaction into the expected string form. In particular, we see how the asymptotic behavior of the gravitational field appears in the scattering.Comment: 20 pages + 2 figures (included as a uufile), LaTe

Dual Method Headphone Amplifier

Many high impedance headphones underperform their full potential when directly connected to the audio source. Amplifiers boost the audio signal and provide the headphones with sufficient power to ensure their maximum performance. The invention of transistors caused vacuum tube implementation to decline, leaving many audiophiles unsatisfied with the transistor’s sound signature. Vacuum tubes and transistors both amplify signals, however the distinct “tube sound” has vanished. We have designed and created a product where the user selectively switches between solid-state transistor and tube amplification to compare the sound signatures of each amplification method. The ability to switch between the solid-state and tube amplifiers creates the ability to achieve a more customized sound for individual songs and improve the user’s listening experience. This requires the design of two separate amplifiers and circuitry to switch back and forth between amplification methods without pausing the music or unplugging any device