DEAT wrote on 2024-12-17, 02:09:
ltning wrote on 2024-12-14, 21:44:
Well I did try the "mode Y" version and got 18.441, a tad up from the previous run. Did anything change between the Oct 10 and Nov 5 versions?
That doesn't sound particularly optimal for a 31.25Mhz 286 - is this running with 1WS? I get the following with a Headland HT12 mobo running at 25Mhz with 0WS and a Cirrus Logic GD5429:
The 5429 is probably a fair bit faster than my ATI Mach8; when I switch to a Mach32 I get about 10% higher performance in e.g. 3dbench. But the HT12 *is* a really fast chipset. This machine is C&T NEAT and it claims to run at 0ws, but it might mean "zero *additional* ws", meaning 0ws above whichever minimum it operates with.
DEAT wrote on 2024-12-17, 02:09:
doom8088
doom2my - 18.124
doom213h - 15.990
That's pretty good indeed. It means I should be at >>20 for doom2my assuming linear scaling. I'll keep tweaking..
DEAT wrote on 2024-12-17, 02:09:Since someone in a Discord server told me that it should be fast enough to be classed as a 486, I decided to also test with a 48 […]
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Since someone in a Discord server told me that it should be fast enough to be classed as a 486, I decided to also test with a 486SLC-40 mobo that has a SARC RC2106A5 chipset (PCChips M396F v2.7) clocked at 33Mhz:
doom8088
doom2my - 26.280
doom213h - 20.933
(snipped the wolf3d stuff, sorry, since I have no basis for comparison there)
The 486 will always be a fair bit faster since it has cache (yes I see you tested without..:) and, I suspect, churns some instructions a bit faster than the 2/386? I don't know if the 486SLC had the same tight pipelining as the i486, but unless you disable the internal cache it will be a very unfair comparison..
DEAT wrote on 2024-12-17, 02:09:and then with the L1 cache disabled: […]
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and then with the L1 cache disabled:
doom8088
doom2my - 18.333
doom213h - 15.658
Now this is surprising indeed. It would seem to suggest that the 486SLC is *really* dumbed-down compared to an i486. I guess the unexpectedly low performance here could partially be due to bus speed differences? The HT12 and my NEAT probably runs the ISA bus at somewhat insane speeds, while your 486SLC probably runs it at the prescribed 7.something MHz.
DEAT wrote on 2024-12-17, 02:09:
The 486SLC mobo does use a PLL for controlling the CPU clock between 33/40Mhz, but it looks like it should accept a crystal oscillator based on the PCB layout - would be interesting to get benchmarks at the same clock speed, but that's a job I'll have to try at some point in the near future.
I have a 386DX-16 here and for some reason I can't get it to perform worse than a 20MHz. I have a motherboard that is supposed to be able to generate clocks for 12, 16, 20, 25, 33, 40, 44 and 50MHz, but the first three seem to give the same real-world results. I'm going to have to replace the clock generator at some point, or perhaps install the same Any_Clk* on some other board to test more.
* https://migronelectronics.bigcartel.com/produ … g-underclocking
The Floppy Museum - on a floppy, on a 286: http://floppy.museum
286-24/4MB/ET4kW32/GUS+SBPro2
386DX-40/20MB/CL5434 ISA/GUSExtreme
486BL-100/32MB/ET4kW32p VLB/GUSPnP/AWELegacy
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