Hello Vogoners today I present you the build that got me started with this hobby in first place.
So I had a couple of VLB cards lying around in storage since the 90s which were likely removed in upgrade process back in the day. In 2020 I decided to find out what they are good for and set out to build a MS-DOS 486 rig.

Components:

• AMD Am5x86-P75 AMD-X5-133ADW (1996)
• Top Motor clip-on socket 3 cooler (1996)
• QDI V4P895GRN/SMT (1995)
• 256KB UMC UM61256FK-15 cache (1995)
• DTK PTI-265W VLB multi i/o controller (1994)
• 12MB 72-pin FPM (1995)
• Trident 7352 Rev. G2 TGUI9440AGi 1MB VLB (1995)
• Sound Blaster 16 Pro CT2290 (1995)
• Serdaco DreamBlaster S2 (2019)
• 3Com EtherLink III 3C509B-C (1995)
• U.S. Robotics internal Sportster 14.4K (1994)
• Teac CD-540E (2000)
• Sony MF920 3.5” (2003)
• Teac FD-55GFR 5.25” (1993)
• Iomega Zip100 ATAPI (2000)
• Apacer AP-FM25644B IDE DOM 256MB (2004)
• Keyboard lock key (origins unknown)
• Beige tower case with turbo display (1995)
• UTT 235WT AT PSU (1996)

Purpose:
I use it for older adventure games, stuff that needs EMS, etc. For later, more graphically intensive and dynamic titles such as Duke3D I use my newer Pentium II build. Also, based on the old photo I sourced a closest resembling AT tower case so with the actual components installed the whole thing bears some nostalgic value to me.

Performance:
The CPU runs downclocked to 100MHz most of the time.
Notably this system overall is not a speedy one compared to some other 486 chipsets such as SiS 85C471.

BIOS v.1.2 Am5x86-P75 at 100MHz and at turbo speed

Neither configuration reaches the reference benchmark numbers.

Storage:
A 40-pin IDE DOM from some 2004 thin client PC suits my needs just perfectly as fast and silent. Thanks to it I freed up both 3.5” bays for the removable media drives. 256MB of disk space is plenty for DOS and the games of the time. It needs a 5V power supply using a JST micro connector. I can transfer data between any of the following: 3.5” 1.44M disks, 5.25” 360K or 1.2M disks, CDs (-R and -RW as well), ZIP100 disks (GUEST.EXE driver), 10Mb Ethernet (Packet driver), and a modem as a last resort. Mostly I just use the floppies.

TODOs:
By now I consider it mostly finished but I shall replace the PSU capacitors and a noisy PSU fan at some point. A PS/2 to serial from Serdaco is also an interesting thing to add. For now a serial mouse is used.

Tips and interesting stuff:

1. Memory testing sound. During the POST this motherboard produces a certain sound through a PC speaker which can be described as ticking or rattling. It doesn’t serve a purpose and can be annoying. Interestingly there is a hidden BIOS option to disable it.
2. This multi i/o card uses “other” serial header pinout, the Intel/DTK rather than the popular AT/Everex . Thus any aftermarket breakout header cable likely won't fit. If like me you need a DB25 serial connector with that pinout your best bet is assembling one yourself.
3. It appears so that Trident 7352 Rev. G2 can come with both 9440 and 9440AGi chipsets. The card I use is pretty fast and can decently run Duke3D in full screen.
4. Socket 3 cooler. While some people just glue the heatsink to the CPU I did not like this approach. So there is a tiny clip-on cooler making a sandwich out of a CPU with a small aluminum heatsink sitting on top of it with a layer of thermal paste. The cooler has plastic tabs which go in the small gap between the CPU and the socket.
5. Suspend instead of turbo. I have tried 2 BIOS versions and while the newer v.1.4 allows running Am5x86-P75 faster it loses the turbo switch function and replaces it with suspend even if you check the relevant hidden BIOS option. Because turbo is important, I stayed with an older BIOS version v.1.2 at the cost of some performance. Similar issue was referenced here with no answer.
6. This 3Com Ethernet card has a RJ-45 socket and using a packet driver you can surf the WWW with a browser called Arachne. Its other connectivity options are BNC and DA-15 AUI. The latter looks very similar to joystick gameport connector so one needs to be careful when plugging stuff. To initialize the packet driver put the following in autoexec:
   Copy code to clipboard

   1LH 3C5X9PD.COM 0x60
   

7. The iomega ZIP100 ATAPI works well in pure DOS using "Guest" driver. I have experienced lockups with its operation until I changed the IDE ribbon cable for a fancier 80-wire one.
8. The AMI WINBIOS is way ahead of its time in my opinion. I also want to highlight this important option called “32bit xfer”. If you are using a VLB i/o card rather than an ISA one you should enable it.
   It has mouse support and fancy menus

   

9. In order to access a number of hidden BIOS options such as write-back cache operation I suggest you try AMISETUP 2.99 by Robert Muchsel.

Photos:

Front view

Back view

The BabyAT builds cable management can get notoriously messy

Thanks for reading any questions are welcome and have a nice day!