The Impact of Hardware and Software Configurations on PCSX4 Performance: A Deep-Dive Analysis
Welcome, gamers. Today, we will delve into a topic that deviates from our usual progress reports. Specifically, we will provide an in-depth analysis of how hardware and software configurations can significantly impact the performance of PCSX4.
Memory speeds are one of the many things that can keep the PCSX4 from running at its best.In our case, PCSX4 stresses memory performance in multiple ways:
Virtualized emulation involves SPUs accessing the main memory via DMA, which is a challenging task to emulate.
VirtX emulation entails two significant categories of memory operations: upload and download. Upload operations comprise transferring textures, shaders, and shader data (such as vertex buffers and register configuration tables) from the host CPU to the host GPU. This process is typically optimized by the GPU driver to occur asynchronously with a high level of batching. Since the data sets are large and transportation occurs through PCI-E, this process is bandwidth-heavy. While we do much to conceal this issue, slow memory or older PCI-E revisions can result in transfer lag, which can significantly affect performance, particularly if a GPU sync is required.
Download operations include transferring textures and arbitrary data from the host GPU to the host CPU. This operation can severely impact performance since we cannot conceal the memory latency for the transfer. Most of the time, the memory in question will be accessed by virt-io buffer without warning, which means we must halt all operations until the GPU processes the required information. Then, we must read all the data back over PCI-E while our CPU thread is blocked. This is why we have the "buffer options" disabled by default to reduce the penalty of this hard stop, as most games might overwrite older GPU-resident data without necessarily needing to read it back later. Therefore, it is not advisable to run PCSX4 with your GPU usage maxed out or close to it since your GPU will not respond quickly enough to these random synchronization requests. However, there is a lot of optimization that can be done in this area, with a high-accuracy predictor that can anticipate whether or not a memory block will be accessed by the CPU soon, thereby enabling the queuing up of GPU instructions before the CPU accesses the memory.