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by deaddodo
661 days ago
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> However, the PS2's GS RAM clocked in at 48GB/s, more than the external memory bandwidth of the Cell (~25GB/s), which meant that PS3 emulation of PS2 games was actually done with embedded PS2 hardware. That's kinda overselling it, honestly. When you're talking about the GIF, only the VU1's vertex pipeline was able to achieve this speed directly. PATH2/PATH3 used the commodity RDRAM's bus (unless you utilized MFIFO to mirror a small portion of that to the buffer, which was much more difficult and underutilized than otherwise since it was likely to stall the other pipelines); the exact same bus Pentium 4's would use a few months after the PS2's initial launch (3.2-6.4GB/s). It's more akin to a (very large) 4M chip cache, than proper RAM/VRAM. As to the PS3 being half that, that's more a design decision of the PS3. They built the machine around a universal bus (XDR) versus using bespoke interconnects. If you look at the Xbox 360, they designed a chip hierarchy similar to the PS2 architecture; with their 10MB EDRAM (at 64GB/s) for GPU specific operations. As to those speeds being unique. That bandwidth was made possible via eDRAM (on-chip memory). Other bespoke designs utilized eDRAM, and the POWER4 (released around the same time) had per-chip 1.5M L2 cache running at over double that bandwidth (100GB/s). It also was able to communicate chip-to-chip (up to 4x4 SMP) at 40GB/s and communicate with it's L3 at 44GB/s (both, off-chip buses). So other hardware was definitely achieving similar to and greater bandwidths, it just wasn't happening on home PCs. |
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Edit: if memory serves, SPE DMA list bandwidth was just north of 200GB/s. Good times.