VOGONS


First post, by jakethompson1

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Hello,

I'm repairing an ISA-386SIQ with battery damage. As pshipkov noted the cache performance is disappointing. The board has no Alter (dirty) RAM and the BIOS programs the chipset as write-back so it is in "always dirty" mode and BIOS settings are quite sparse.

The datasheet shows that the 85C460 supports write-through cache as well. Switching to it reduces the readings in cachechk from 95 to 62. You can also use this quick utility to do this.

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Reply 2 of 5, by jakethompson1

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pshipkov wrote on 2023-05-21, 23:24:

Did you do other preliminary tests ?
Anything out of ordinary ?

I'm actually booted into (old) Linux on it right now as I wanted to play with SSH with modern cryptography (all the djb stuff ed25519/curve25519/chacha20/poly1305) on such an old CPU. It actually works pretty well; the initial SSH connection does take about 50 seconds using public key authentication though.

Reply 4 of 5, by jakethompson1

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pshipkov wrote on 2023-05-22, 01:18:

Ok, good to hear.
But now i am curious - what's with the modern cryptography on a 386, from all other possible activities ? : P

I was just wondering whether it would work to backport a current ssh rather than have to un-harden the ssh client (or server) from a modern machine, how slow it would be, and I was curious about which part of the SSH implementation is the bottleneck. It was the chacha20 inner loop as well as the sha256 compression function. And I'm not and was not much of a gamer so I don't have the extensive game library that some have here 😀

Reply 5 of 5, by pshipkov

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Not into games ?
A dangerous statement.

Kidding aside - i relate to what you said.
Recognized early that making is more rewarding than consuming, so the playing part was short.

retro bits and bytes