Here is an comparison page with some interesting numbers that doesn't seem to be complete poppycock:
https://segaretro.org/Sega_Saturn/Hardware_comparison
This article has some inaccuracies/misleading statements.
"In addition, the
VDP2 has its own internal geometry processing unit for its 3D planes, allowing both SH-2 and the SCU DSP to calculate geometry for the VDP1 polygons."
VDP2 displays a whopping 2 quads without shading, not exactly a tangible T&L load. And I think you actually do have to do a lot of setup to apply perspective correction.
"In terms of polygon rendering
fillrate, the PS1's
GPU and the Saturn's
VDP1 have similar performance. The GPU has a performance advantage for large polygons and
flat shading, while the VDP1 has a performance advantage for small polygons and
Gouraud shading. The GPU uses multiplicative Gouraud shading,
[8] which halves its fillrate,
[9] whereas the VDP1 uses additive Gouraud shading,
[8] which has less of an impact on fillrate."
PS1's GPU is nominally 2 cycles per pixel without shading or texturing and 1 cycle per pixel with, while VDP1 is simply 1 cycle per pixel (and PS1 GPU is clocked higher).
"The Saturn's
VDP2 has a higher rendering fillrate than the PS1's GPU."
Let's calculate it. VDP2 can draw 6 layers at up to 352x240, 60Hz (there's a higher resolution mode but it cuts down on the number of layers, also this is assuming NTSC). Or about 30.4 MPixel/s.
PS1 GPU can draw 2 pixels/cycle with non-transformed sprites or flat shaded pixels, or up to ~67MPixel/s. With texturing (sprites) it'll almost always be lower because of contention with the VRAM/SGRAM for cache fills, unless you have a very bland workload that runs purely from the texture cache. Still, it's probably pretty realistic to exceed 30.4 MPixel/s. But this is just a raw fillrate comparison and says nothing about the features behind that fillrate.
On that note, the VDP2 fillrate values they give for that table make no sense.
"while the VDP2's textured infinite planes are rendered with true
perspective correction"
So long as the plane is not tilted on the Z axis, and the game calculates the different perspective ratios for each scanline. It's the same as SNES's mode 7 in this regard; the perspective is fixed per-scanline.
"The VDP1's quad polygons are rendered with
forward texture mapping (a form of perspective correction)"
Not a form of perspective correction at all.
"medium polygon accuracy (resulting in seamless polygons)"
PS1 and Saturn have exactly the same "polygon accuracy"; vertexes are submitted as integer screen coordinates.
As far as any of the comments about using the DSP for any kind of 3D goes, I don't know of any example of a developer that did so definitively. I'd be happy to see some source that shows this, via actual analysis of game behavior and not comments in an article which can often be inaccurate (I see no way that anyone could have used it for "transparencies" for instance...)
"In terms of transparency, the PS1's GPU is more effective than the VDP1, whereas the VDP2 is more effective than the PS1's GPU."
That's not entirely true, eg PS1 GPU has subtractive blending and VDP2 doesn't.
"The VDP1's additive Gouraud shading displayed significantly more shades, resulting in smoother shading"
This is just totally wrong.
"as the Saturn's VRAM has low latency, with an access time comaprable to the PS1's texture cache."
No way is this true, it didn't use some kind of magic SDRAM that defied all limits of the technology to make it as fast as a small on-chip SRAM, in fact it used an off the shelf SDRAM part. I'm sure VDP1 fetches multiple 16-bit texture words in advance to hide latency (one reason why they used forward rendering...) and I'm sure that there were circumstances where VDP1 stalled waiting for textures. Maybe on those small polygons that they claimed Saturn is better at without reference.
"In comparison, the PS1's VRAM has a latency almost twice as high as, with almost half the access speed of, the Saturn's VRAM."
Almost half the "access speed"? They mean bandwidth? Odd how that works when Saturn uses 16-bit SDRAMs at a lower clock than PS1's 32-bit VRAM/SGRAM.
"The Saturn's VDP1 and VDP2 are capable of single-cycle VRAM access,"
Ah, here's where their confusion comes from. They're grossly misinterpreting the VDP2 documentation. "Cycle" in the linked terminology has nothing to do with CPU (or SDRAM) clock cycle, it refers to a loop of memory accesses performed by the VDP2. These accesses are also heavily pipelined (overlapping with each other to hide latency), which the documentation also describes although in super confusing terms and diagrams.
"The SGRAM's lower latency was only used for faster transparency blending and improved Gouraud shading."
Nit-picking, but the improved gouraud shading has nothing to do with the SGRAM, it was an update to the GPU itself.
On that point, I had no idea the original GPU only shaded with 5-bits, all my tests were with newer PS1s. I'll have to amend my previous shading explanation to include this...
"This still results in fewer shades than the Saturn's VDP1, which produces 15-bit Gouraud shading."
Okay this is just too much. They're using per-channel bit counts for PS1 vs entire color (three-channel) bit counts for Saturn. Saturn has 5-bit Gouraud shading, like the original PS1.
I'm not going to get into that comparison table just yet, it's just full of things that make no sense to me. Part of the problem seems to stem from the faulty claim that VDP2 runs at twice the clock speed as VDP1 and the SH2s...