If you want to use a Cyrix based CPU in a 386 motherboard, try and find one that supports the onboard level 1 cache in the BIOS (otherwise, you will have to use the Cyrix software to enable it).
Unfortunately, I cannot really comment on what would be regarded as the best 386 motherboard, but I have two (386DX only) motherboards that seem to have worked fine for me.
- The first one is an Elitegroup Computer Systems (ECS) FA386 motherboard with the UMC UM82C481BF & UM82C482AF chipsets.
This motherboard works very nice with both an AMD 386DX 40 MHz CPU and a Cyrix 486DLC 40 MHz CPU in conjuction with a Cyrix 87DLC-40GP FasMath coprocessor.
This motherboard's BIOS supports the CPU's onboard level 1 cache with no problems.
I initially struggled a bit to find a manual for this motherboard, but after an extensive search, managed to find the motherboard settings in some "PC Engineer's Reference Book".
- The second one is a Chicony CH-386-33H/40H motherboard with the UMC UM82C481A & UM82C482AF chipsets (not too sure which of the former chipsets are the latest between the two motherboards).
This motherboard also works very nice with the two CPU's mentioned in my first point and the BIOS also supports the Cyrix 486 DLC's onboard cache.
However, the only problem I initially ran into was when I first installed the Cyrix 486 DLC. The PC wouldn't boot up properly, until I went into the BIOS and loaded the BIOS setup defaults, saved and restarted.
Regarding hybrid 3/486 motherboards:
My very first PC (a 486DLC) came with a hybrid 3/486 motherboard (a Jetway brand), utilising the OPTI 495XLC chipset.
Despite later on swopping the CPU out for an Intel 486DX 33 MHz, I could never get a Vesa Local Bus graphics adaptor to work properly on this motherboard.
Unfortunately, the motherboards' BIOS died a couple of years ago and I've recently been looking out for a replacement BIOS.
A couple of months ago, I came across another hybrid 3/486 motherboard (a Dataexpert EXP3406) also utilising an OPTI 495XLC chipset.
I've recently been running some benchmark tests on this motherboard, using AMD 386DX 40 MHz, Cyrix 486DLC 40 MHz, Intel 486DX 33MHz and Intel 486DX2 66 MH CPU's.
Although I'm still conducing benchmark tests, my Cyrix 486DLC 40 MHz runs marginally faster (by using NSSI 0.60 & Landmark Speedtest 2.0) in my "standard" 386 motherboards, compared to the hybrid 3/486 motherboards. BIOS settings between the two were the same, but I suspect it's the UMC chipsets that are slightly faster.
However, my experience has been that the Vesa Local Bus slots don't work properly on either of my two 3/486 hybrid motherboards - I tried two different Vesa Local Bus graphics cards on the EXP3406 and the motherboard just gives me a graphics card beep error code every time (i.e., it cannot "find" the graphics cards).
ISA graphics card performance (on the EXP3406) has also been disappointing with my ET4000AX card, since with Landmark's Speedtest 2.0 it caps out at around 3810 chr/ms (by comparsion, it runs at 5120 chr/ms on my "standard" 386 motherboards). This has also come through on the Doom benchmark test, with almost 1 frame per second difference between the two.
As already stated, you are going to spend a fortune on a Cx486DRx2/Ti 486SXL2. For much cheaper, you can just as well then get yourself an Intel 486DX2 66 MHz on a 486 based PCI or, if you really like, VLB motherboard. Most Vesa Local Bus motherboards I've come across still requires expansion cards, while most PCI 486 motherboards have integrated controllers onboard.
If you want to go with a 386 build, then go for either an AMD 386DX 40 MHz or a Cyrix 486DLC 40 Mhz on a standard 386 motherboard. From what I've heard, the Vesal Local Bus performance on a 386DX (if you can get it to work) wouldn't make a much of a difference, since you are limited by the speed of the CPU anyway.
However, once you start moving onto a Cyrix 486DLC 40 MHz, then you are already moving into 486DX 33 MHz territory and you then need to ask yourself whether you're not better off with a 486DX 33 MHz on a 486 motherboard.