Repairing a Very Slow FIC 486-VC-HD Motherboard

Today I repair and test a budget model FIC 486-VC-HD motherboard. This board refused to boot due to a dead RTC module, but also had terrible memory latency. Join me today as I get this board repaired and dig into a surprising caching problem that impacts many 486 boards from the early 90s. DS12887A+ RTC modules from DigiKey: https://www.digikey.ca/en/products/de... 24-pin DIP sockets: https://www.digikey.ca/en/products/de... Necroware’s nwX287 modules: https://github.com/necroware/nwX287 ** If you enjoy my content, please consider subscribing. Blog: https://vswitchzero.com/ Bluesky: https://bsky.app/profile/vswitchzero.com Mastodon: https://bitbang.social/@vswitchzero Retro Hardware Discord Server:   / discord   Please note: I have retired my Patreon page. Please see the following blog post for more info: https://vswitchzero.com/supporting-th... ** 00:00 Introduction 00:34 It’s Broken 01:47 RTC Replacement Options 02:23 Replacing the RTC Module 04:48 Terrible Memory Performance 06:01 Disabling the L2 Cache 06:23 L2 Cache Configuration 07:14 The Dirty Bit 09:37 Adding AlterRAM 10:07 An Expensive Mistake 11:24 Conclusion