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AMD 486 SV8B vs NV8T — Is there a performance difference

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First post, by byte_76

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My motherboard manual lists the AMD DX4-100 SV8B as “Enhance” and the DX4-100 NV8T as “No Enhance”

SV8B = Write-Back
NV8T = Write-Through

I have both of these processors and benching them in this same motherboard using Phil’s Dosbench suite, they score the same results.

To be sure, I’ve used CHKCPU which correctly identifies Write-Back (SV8B) and Write-Through (NV8T) configuration for each processor respectively.

So just out of interest, have you found any difference in performance between these two processors in your own tests?

The board has L2 cache configured in WB mode with 32MB of ram.

Last edited by byte_76 on 2025-04-23, 13:40. Edited 4 times in total.

Reply 1 of 1, by mkarcher

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The memory benchmark in speedsys (e.g. from Phil's Suite) doesn't profit from write-back cache in the "writing" bench, because the way that benchmark works, the writes in the "write" benchmark nearly all miss the cache. You should get some improvement of the "moving" score for sizes below 16KB, though. They say you typically get some performance benefit on average by using the SV8B over the NV8T, if the SV8B is configured to operate in WB mode. If the SV8B is configured to operate in WT mode, the performance is identical to the NV8T. IIRC most of the CPU identification utilities explicitly list the cache mode (WB or WT) and the multiplier (x2, x3 or x4) for SV8B processors.

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