The Shuttle HOT-409 is a 486 VL motherboard, nothing extraordinary in fact. It has two combined VL + 16-bit ISA slots, four 16-bit ISA slots and one 8-bit ISA slot. It uses the OPTi 495SX chipset, takes up to 32 MB of 30-pin SIMMs, supports up to two hard drives on an IDE controller (up to 504 MB each; controller is not included on the board) and can be equipped with anything from a 486SX-25 to a 486DX/2-66 (and with a voltage regulator socket, a DX/4-100). A little ton-like rechargeable battery (NiMH or NiCD) serves as the CMOS battery; an external one can also be attached. That's it. Frills? Not really. Oh, wait: You can alter lots of interesting options in the BIOS setup (by "interesting", I mean things affecting performance); there aren't many chipset settings that cannot be changed there. You can even overclock the ISA bus if you like, since the clock can be selected from 1/3 to 1/6 of the external CPU clock (i.e. 33 MHz with a DX/2-66 CPU). The board is not a speed king, but the performance is quite reasonable once you've done some fine tuning.
Need a board manual? Look here.
When tuning memory and cache waitstates/timings in Advanced Chipset Setup, be sure to disable the "AUTO Config function". Otherwise these settings will not be used.
At 33 MHz you should be able to run at zero memory waitstates (provided you have reasonably good memory modules), equally little cache write waitstates and 2-1-1-1 cache read timing even when both memory banks are in use. At 40 MHz, I encountered considerable instability (although none of the memory testers used found errors); probably the most conservative settings would have fixed that (I returned to 33 MHz after I had trashed Win95's registry and was busy reinstalling it for a while). Perhaps the DX/2-66 didn't like being overclocked to 80 MHz, who knows. (Cooling was more than adequate.)
The jumper settings for 40 MHz system clock (not described in the manual):
Shuttle support says the fastest processor you can put into this board is a 486DX/4-100 with a voltage regulator socket.
Want to get the most out of the 495SX chipset? This little program (for DOS) alters a chipset setting (index 21h, control register 2, bit 6 set to 0, if you'd like to do the same in CTCHIP) to get even more (cache) performance out of the thing. Thanks to Christian Zietz for writing this!
Changes in the new BIOS:
Download the new BIOS. (This file is provided as-is with no warranty implied - don't fry your board, EPROM or anything else.)
You can contact me via my contact page.