Hello! Just want to say, this forum has been really helpful. I've been restoring and upgrading a compaq portable 286 and 386 and this forum is a lifesaver! 😀

I do have a question though that I could not find a clear answer to.

What is the best way to upgrade the CPU in the Compaq Portable 386? It runs with a 40 mhz crystal, so originally, I thought a Cyrix Cx486DLC-40GP would be best but I could not find one, but instead I found a Cyrix Cx486DLC-33GP and then tried to activate the L1 Cache but then I got an error saying that I needed a flush board since the system board could not activate the cache. Without the Cache activated I don't think the Cyrix upgrade is much use.

Then I found out that the Cyrix Cx486DRx has Cache Coherency (which I think means that the Cache doesn't rely on being activated by the system board). The problem with the Cyrix Cx486DRx however, is that it comes in 25 -> 50 and 33 -> 66 versions, but neither of those match up with my 40mhz board. Will the Cyrix Cx486DRx work? If so, which one would be more effective?

Also, which math co-processor would be best? For the Cyrix Cx486DRx (or if I should stick with the Cx486DLC-40GP?)

Thanks for your help guys!