Uncreative Labs

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

My experience upgrading a 286 to a 486SLC was rather painless, and the additional cache memory worked right out of the box. However, recently I have been having some serious headaches involving upgrading a 386 to a DLC. Even though I am running a motherboard that is specifically designed to work with the DLC, enabling the cache has created nothing but problems. It causes some crap with the A20 line and prevents me from loading HIMEM.SYS. Intsead it presents me with the error "unable to control A20 line". Because of this I cannot enter protected mode which totally defeats the purpose of upgrading. I've tried just about everthing imaginable to fix this A20 mess, but nothing seems to work. According to the newsgroups this seems to be a pretty common issue with the DLC. Anybody in here had this problem and fixed it?

Joined: 20 Nov 2004 Posts: 589 Location: Shandong, China

I was able to fix my problem by enabling a CPU register that sets the first 64k of each memory segment non-cacheable before enabling the L1 cache. It worked like a champ, except for a minor draw issue with the Mach64 VLB in windows. I swapped in a Mach64 ISA, and I was surprised to see that it was actually slightly faster than the VLB version?!?! The draw issue went away too.

System performance is pretty decent now too. I don't have the exact numbers a the moment, but I recall memory scores were in the 17MB/sec range, video scores at 800x600@64k were 2.9MP/sec (with the 386DX it was 2.2), disk throughput is around 4.8MB/sec, CPU speed was just a hair short of a 486DX/33, and FPU performance was about 75% of a DX/33. I'm currently using an overclocked intel 387dx-33. I plan to swap to Cyrix87-40 when I find one of a late revision.

These 486SXLs really fly if you can get them working....but doing that is a pain in the ass.