5 ms·
> 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
by deaddodo 2y ago
> 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.
- twoodfin 2y agoGrowing up with the tech press in this era, “commodity RDRAM” is a funny phrase to read! As I recall, the partnership between Intel and Rambus was pilloried as an attempt to re-proprieterize the PC RAM interface in a similar vein to IBM’s microchannel bus.
- deaddodo 2y ago"Commodity" meaning "something that could be bought at the store".
- rowanG077 2y agoWhy is it funny. You could just go to a computer store and buy RDRAM.
- twoodfin 2y agoIt wasn’t a commodity! It was a single-owner proprietary technology. You needed a license from Rambus to manufacture it. And at least at the time it commanded a premium price over true commodity DRAM. People on Slashdot got really worked up when Intel signed a deal with Rambus to make RDRAM the only supported technology on Intel x86—from which they relatively quickly backtracked. Anandtech (sniff) of course has great contemporary background: https://www.anandtech.com/show/545 https://www.anandtech.com/show/545
- chaboud 2y agoI think that’s fair. It was, in effect, a cache and DMA target. A similar scheme was present in the Cell, where the SPE’s had 256KB of embedded SRAM that really needed to be addressed via DMA to not drag performance to the ground. For low-level optimization junkies, it was an absolute playground of traps and gotchas. Edit: if memory serves, SPE DMA list bandwidth was just north of 200GB/s. Good times.