Hello all! I have been reading quite a bit on these forums recently as I am building my first retro gaming PC, but this is my first post. I have built a few modern PC's, but haven't build a 486 since the 1990's. I am getting parts/pieces from eBay and local sources. I have run into a problem and I am hoping to pick the bright minds here on VOGONS and see if I can get some help. My system consists of the following parts:

a Chicony CH-471a Rev 3.0 VLB motherboard
Intel 486 DX2-66 (SX955) processor
Diamond Speedstar Pro VLB graphics card
Sound Blaster Pro 2.0 sound card
2x36 (8MB) FPM Parity 70NS 72-pin SIMM x2 memory modules
ISSI IS61C1024-15N 128k x 8 High Speed CMOS Static RAM x4 for 512 KB of L2 cache
ISSI IS61C256AH-15N 32k x 8 Static RAM x1 for TAG SRAM for L2 cache
Imation 3.5" internal floppy drive
Chinon 5.25" internal floppy drive
Western Digital Caviar 420 MB 3.5" IDE hard drive
HP Panasonic CR-583-B 8x IDE CD-ROM drive
Tyan S1345 VL400GW-VI VLB IDE/Multi-IO controller card
UMC UM9008F NE2000 compatible 10Mpbs 16-bit ISA LAN network card
Bestec BPS-2994-4U AT 350W power supply
Microsoft serial PS/2 compatible mouse
IBM Model M keyboard

The problem that I am having is that approximately 98% of the time it will freeze on boot-up. When I turn the computer on, the initial screen will appear and it will display the processor type and then go through the memory test. It will flip through all of the memory then the "press DEL for setup" and "press ESC to skip memory test" messages will disappear. It will then freeze at this time, requiring a reset or turning off/on. In troubleshooting the problem, I have removed all of the cards except the graphics card and I/O card. I have also changed and replaced the memory and cache multiple times. I have gone through the BIOS and changed almost all of the settings in there to get it working. Since completing the build (about a week) it has booted all the way through about 5 times. The next screen (after the memory testing) is the screen that shows the processor type, speed, memory, cache and ports installed. After that, it will try to load a disk/hard drive. During one of the 5 times I have gotten it to go this far, I was able to install MS-DOS 6.22 to the hard drive. During one of the other times I was able to boot to DOS, I was able to install a game (King's Quest IV). The game loaded and I played it for about 5 minutes before it froze and required a restart. I have gone through the motherboard manual and made sure all of the jumpers are correct. I even realized that the CPU is one of the later Intel CPU's that has write-back cache instead of write-through cache. My motherboard has special jumper settings for this processor (P24D). Changing to these jumper settings didn't make a difference either.

One interesting thing is that when I disable the CPU cache in the bios, it will get past the usual spot it freezes at (after the memory test) and will get to the next screen. It will then freeze after it lists all of the ports and requires a restart. When I turn the CPU cache back on, it will again freeze after the memory testing. Again, I have tried dozens of different bios settings over the past week without any consistent success. One other interesting this is that when I do get it go boot all the way to DOS, when I press the reset button, it will continue to boot to DOS, however, when I turn the power off and turn it back on, it will again freeze at the usual spot.

My thoughts are: I am stupid for trying to use 2 VLB boards at the same time. I didn't realize this when I was building the system, but after doing some further research, it looks like getting 2 VLB cards to work at the same time is very difficult. I have ordered an ISA I/O controller and will try this as soon as it gets here. This would be an easy problem to fix. In the meantime, I did take the VLB I/O controller card out and tried to boot but it froze at the same spot, with the same change when disabling the CPU cache, so I'm not sure if replacing the I/O controller will do the trick, but I am hopeful.

I have also ordered a new CPU, thinking it may be a CPU problem, especially given the change when disabling the CPU cache.

I currently don't have a CPU heatsink/cooler installed, but the problem happens during the first start-up after sitting all night, so I don't think heat would be an issue. I did buy a heatsink/fan to install and see if it makes a difference.

Is it a graphics card issue? I have another VLB card that I have tried and it has the same problem. Would it help to get an ISA graphics card and try it?

Is it a motherboard issue? Would it be worthwhile to buy a new motherboard and try it?

The motherboard did not have a battery when it was listed on eBay, so the guy I bought it from soldered a CR2032 connector to the battery connections. I have installed a fresh CR2032 battery. Could this be an issue?

Anyways, I know this is a very lengthy post and many people won't make it this far, I'm sorry. I just wanted to give as much information as possible. I am frustrated and eager to get playing some vintage computer games. I have a Roland MT-32 and SC-55 waiting to get some use! 😀

Thank you all in advance for any advice you can provide!