ellroy
kiwifarms.net
- Joined
- Feb 2, 2021
I think you’re getting things mixed up. Cell refers to the overall chip, which in regards to the PS3, meant one Power Processor Element (PPE) and seven Synergisitic Processing Elements (SPE; the eighth exists but is physically separated and not used). The PPE was the Power PC core designed to do scheduling to send calculations to the SPEs. The SPE’s can access memory through an intermediary device on the chip called the memory flow controller (MFU). Because of how complicated this is and how compiler dependent the processor became, this is where developers hit a roadblock.It was pretty powerful in a special way but that was then counteracted by the GPU not being the best, it still used different execution units for pixel and vertex shaders and some corners seem to have been cut there. Naughty Dog and other have talked about how they offloaded the GPU by sending vertex shader work to CELL(along with other graphics tasks when appropriate). There are both blog posts and Siggraph presentations/papers about this, it's pretty interesting for people that find this interesting, it is absolute torture to everyone else.
Some early games only ran on the PPC CPU because CELL was a tricky beast to figure out. On tricky thing was that CELL itself couldn't read or write to system RAM, iirc, so the PPC CPU had to feed it data from either the XDR or GDDR3 memory pools, then collect it when done and write it back to wherever it is supposed to be. Each CELL SPE had 256KB to work with and that's not a lot, it needed constant attention from the general purpose CPU to get the most out of it. The people at Naughty Dog could run that shit like clockwork while other developers struggled.
In the early days, Devs used the PPE do most of the work since they couldn’t figure out how to efficiently schedule tasks for the SPE’s. Skyrim’s PS3 release pretty much used the PPE and one of the SPE’s out of an available six. Devs had to use a different instruction set to use the SPE’s so they had to write code in a way so the compiler would recognize it for the SPE. Imagine only having a degree in CS, writing game code for Intel processors in school and then having to work on this vastly different architecture. Sony eventually wised up and sent subject matter experts to their in house studios to teach them how to use the processor and Naughty Dog became the most technically proficient.
Concerning the GPU, the system used a scaled down version of a 7800 GTX chip from NVidia and this chip was over a year old by the time the PS3 hit market. Combine this with limited system RAM (256 MBs was the biggest complaint the cluster operators had when they would install Linux), the PS3 was an over and under performing console when it came to its hardware.
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