486 Upgrade

My mate, Matt Manks has donated a Kingston 5×86 TurboChip upgrade board for my 486.

It was a bit of a pain to remove the AMD 486DX-40, but with some careful work, I was able to remove it.

I had to pop the entire motherboard out to be able to change the base clock frequency from 40MHz to 33MHz, but once it was done, and the new chip was carefully inserted I fired it up and got…

…and that was it. I waited and waited, but nobody was home.

First thing I tried was swapping the Multi I/O card for an ISA one (As IDE had been a bit flaky on VLB with a 40MHz FSB). No change.

Matt suggested disabling the on-chip cache, just in case, and, on that advice, I tried disabling all the caches and it booted straight into DOS!

W00t!

A bit more fiddling, and it turned out it was the on board cache that was the problem. Disabling that gave me a system that booted fine. I’ve since tried fiddling with the BIOS settings around cache, to no avail. For now I’m just running it without a second level cache.

Benchmarks!

DOOM Before

timed 3863 gametics in 7232 realtics (10.2FPS)

DOOM After

timed 3863 gametics in 3979 realtics (18.28FPS)

Landmark 2 before

Landmark 2 after

Speedsys 4.78 before

Speedsys 4.78 after (Note the drop-off in the memory test caused by the lack of L2 cache)

3d Bench 1.0 Before

3d Bench 1.0 after

All in all, it’s about 2-3 times faster, depending on the test. If I can get the cache working, we should be able to eke some more performance out of it.

Again, a huge thanks to Matt for the upgrade!


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