So, in a bid to create the fastest "386" (short of an IBM 386SLC, for now), I have just acquired a TI 486 SXL-40 off eBay for under $30. This is the one with 8 Kb cache. I also have a DLC-40, and a couple co processors (a Cyrix, sometimes ID'd as a C&T, and an IIT).

I decided to put them through the wringer on my 386 generic OPTi ISA board (from which I had to unsolder the 386 DX-40 CPU before I could get it to POST with any other CPU installed, including another 386 DX-40 CPU...). I do not know anything about this board except that, like my manual-unobtanium EISA board in another thread, there doesn't seem to be much out there about it. BIOS signature is 40-0100-001123-00101111-060692-opwbsk-f.

The tests were done on the same board using the same boot sequence. No alterations were made in BIOS - L1 and L2 cache enabled. Software was run from an internal IDE flash drive. The system has 16 Mb RAM installed, 256k L2, 1Mb TSENG-4000 ISA video card. I wanted to throw on a 386 DX-40 but it was getting late. I can always add that info later if there's enough interest, but I presume the values will be very low.

I did not run any video benchmarks, as I was interested in the raw performance of these combinations of CPU/FPUs

Hardware:
CPU
- Cx486DLC-40GP
- TI 486 SXL-40
FPU
- CX-83D87-40-GP (seen as C&T 38700)
- IIT 4C87DLC-40

Motherboard - Generic OPTI AT ISA 386 40-0100-001123-00101111-060692-opwbsk-f

*with any processor / co processor installed, speedsys sees it as a DLC @ 13 MHz. Only when each CPU is inserted separately does it display the correct speed. I have pictures of this event using all combinations. Performance seems to suffer when any FPU is present with any CPU using the speedsys benchmark. This is why CPU solo tests were also done at the bottom of the page. The results are strange.

**NSSI saw the IIT co processor at 38 MHz.

Software versions
- Speedsys 4.75
- NSSI 0.60.45
- Syschk 2.41
- PC-CONFIG V7.31
- Sysinfo 8.0

___________________________RESULTS__________________

TI + Cyrix co pro

Speedsys - 10.14
NSSI - 19044 Dhrys/s (just above an Intel 486 DX 33)
5564 KWhets/s
SysChk - Throughput 104.65 MHz (20392 Char/sec)
PC-Config - (IBM-PC speed compare) 4500%
Dhry/KWhet - 16800, 2192
Sysinfo - 65.5 (computing index, around an Intel 486 DX 33)

TI + IIT co pro

Speedsys - 8.9
NSSI - 18949 Dhrys/s (between an i486DX-33 and Am486DX-40)
5311 KWhets/s
SysChk - Throughput 104.65 MHz (20392 Char/sec)
PC-Config - (IBM-PC speed compare) 4500%
Dhry/KWhet - 16800, 2012
Sysinfo - 65.6 (computing index, around an Intel 486 DX 33)

Cyrix DLC + Cyrix co pro

Speedsys - 10.14
NSSI - 16901 Dhrys/s (just below an Intel 486 DX 33)
5557 KWhets/s
SysChk - Throughput 99.05 MHz (19227 Char/sec)
PC-Config - (IBM-PC speed compare) 4600%
Dhry/KWhet - 14400, 2170
Sysinfo - 65.5 (computing index, around an Intel 486 DX 33)

Cyrix DLC + IIT co pro

Speedsys - 8.9
NSSI - 16901 Dhrys/s (just below an Intel 486 DX 33)
5296 KWhets/s
SysChk - Throughput 99.05 MHz (19387 Char/sec)
PC-Config - (IBM-PC speed compare) 4600%
Dhry/KWhet - 14400, 1990
Sysinfo - 65.5 (computing index, around an Intel 486 DX 33)

TI only

NSSI - 19044 Dhrys/s (beween an i486DX-33 and Am486DX-40)
Speedsys 20.7

Cyrix only

NSSI - 16901 Dhrys/s (pretty much on par with an i486 DX-33)
Speedsys 20.7

It seems the best combo is the TI SLC and the Cyrix FPU. I seem to recall reading as a kid in the 90s that Cyrix did in fact make very good FPUs.

Does anyone else know if there was a better 40MHz 80387 based FPU? I wonder if the 38 MHz IIT chip would be just as good or better than a Cyrix if two more MHz were added (if that's even being reported properly). It would be interesting to see how an i387 fares, but the fastest one I have, or in existence, is a 33MHz version. There's almost no point to checking it out.