I haven't scratched around much, but just by looking at the chipset numbers and what they supported, my guess would be that they had different target markets (business versus consumer, feature wise, etc.).
This is similar to your 430HX & 430VX Pentium 1 chipsets and your 440EX & 440BX Pentium II chipsets (which were also released at the same time, respectively).
From what I could gather the Saturn II chipset was meant to "fix" problems with the earlier Saturn (420TX) chipset.

The Asus PVI-AP4 used the 420EX (Aries) chipset and then you had the Asus PCI/I-486SV2 that used the 420ZX (Saturn II chipset) - this should help you to track down some reading material and opinions on the performance of the motherboards and their related chipsets.
Doesn't seem like the former was a very popular motherboard: ASUS PVI-486AP4 486 board any good?

Seems like they used the Aries chipset for "combo" VLB/PCI motherboards (probably because the chipset could support up to 50 MHz FSB), whereas the Saturn II chipset was mostly used only for PCI implementations (due to only supporting a maximum FSB of 33 MHz).

Aries is the cheaper, more integrated one, Saturn II is the more advanced one. Like jesolo said, the difference is similar to 430HX vs 430VX. I don't have a Saturn II board to compare it with my Intel Ninja Aries based board, but it's still quite fast even without L2 cache. The Aries chipset also has an integrated local-bus-like IDE controller.

One user mentioned that the Aries chipset may not be capable of L1 in write-back mode.
https://groups.google.com/forum/#!topic/alt.c … sus/nvRt8GneAjY

The AP4 does not support the Am5x86 or Cx5x86. There are a lot of complaints about that board.
https://groups.google.com/forum/#!topic/comp. … ips/KzDvANVp2VE

The Asus PCI 486SP3G, which contains a Saturn-II chipset, was noted do not get as good of performance as UMC 8881-based boards. Another user, Artex, mentioned "Intel Saturn II chipset really blows goats."
Artex's Build of the Week: AMD DX4/100 SV8B WB (Write Back Enhanced)

There was one comment that L1 write-back mode on the PCI 486SP3G is problematic for Am5x86 and Cx5x86 chips, although not so with the AMD DX4 w/8KB write-back cache.
Build 486's And They Will Come! Suggestions please!

I cannot find any information on the Asus PCI/I-486SV2. Are you mistaking this model with the VL/I-486SV2, PC/I-486SP3G, or PVI-486SP3G? The latter suffers from slower PCI performance due to VLB bridging.

feipoa wrote:

I cannot find any information on the Asus PCI/I-486SV2. Are you mistaking this model with the VL/I-486SV2, PC/I-486SP3G, or PVI-486SP3G? The latter suffers from slower PCI performance due to VLB bridging.

I found these links on this motherboard (Asus PCI/I-486SV2):
http://rog.asus.com/articles/events/90s-pc-bu … s-motherboards/
Looking to build high-end 486 - any suggestions?

This one, unlike the PVI-486SP3G, did not have VLB slots.

I remember when I tested the AP4 and SP3G boards, there were no problems with the Am5x86. On both boards L1 WB mode worked with the latest bios versions. The CPU was reported as 486DX2 132 MHz but I experienced no compatibility issues. The SP3 features the original Saturn chipset (420TX) , which does not support L1 WB mode. But this is a different board. Saturn boards were expensive back in the day so they are somewhat rare these days. Performance wise I never saw a chipset with better memory throughput. PCi performance was also excellent. On the Aries memory performance is very medioocre, maybe the worst of all 486 PCI chipsets.

PCI/I-486SV2 does not exist. Also there is no PVI-486SP3G. Please do not mix alle the board names together.

VL/I-486SV2 --- SiS 461
PCI/I-486SP3 --- i420TX
PCI/I-486SP3G --- i420ZX
PVI-486AP4 --- i420EX
PVI-486SP3 --- SiS 496

jesolo wrote:

I found these links on this motherboard (Asus PCI/I-486SV2): http://rog.asus.com/articles/events/90s-pc-bu … s-motherboards/ Loo […]
Show full quote

feipoa wrote:

I cannot find any information on the Asus PCI/I-486SV2. Are you mistaking this model with the VL/I-486SV2, PC/I-486SP3G, or PVI-486SP3G? The latter suffers from slower PCI performance due to VLB bridging.

I found these links on this motherboard (Asus PCI/I-486SV2):
http://rog.asus.com/articles/events/90s-pc-bu … s-motherboards/
Looking to build high-end 486 - any suggestions?

This one, unlike the PVI-486SP3G, did not have VLB slots.

Did you look at the photograph of the motherboard under that first link? Although the text title says PCI/I-486SV2, the motherboard has PCI/I-486SP3G written on it.

Yes, I did notice that. But, I wasn't sure which one was correct (they could very well have attached a photo of the wrong motherboard), but thanks for clearing that up.

BastlerMike wrote:

I remember when I tested the AP4 and SP3G boards, there were no problems with the Am5x86. On both boards L1 WB mode worked with the latest bios versions. The CPU was reported as 486DX2 132 MHz but I experienced no compatibility issues. The SP3 features the original Saturn chipset (420TX) , which does not support L1 WB mode. But this is a different board. Saturn boards were expensive back in the day so they are somewhat rare these days. Performance wise I never saw a chipset with better memory throughput. PCi performance was also excellent. On the Aries memory performance is very medioocre, maybe the worst of all 486 PCI chipsets.

Sounds like PCI/I-486SP3G --- i420ZX is the one to shoot for. It is supposed to support memory interleaving, however recent posts by Artex revealed that memory throughput on the Saturn-II is worse than, both, UMC8881- and SiS496-based boards.

So it's not just me. The Asus naming conventions were really damn confusing.

Three different 486 motherboards with "486SP3" in the title. Asus was certainly suffering from lack of nomenclature creativity.