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Octek Rhino 15+ (and other card's) undocumented bus settings

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First post, by gerrokarp35

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Hello dear members of this forum

I am currently messing with an Octek Rhino 15+ motherboard, with a K6-2 333MHz CPU, and learning its quirks in the meantime.
One thing that's driving me insane (apart for Windows 95, it's sooo much finicky than 98SE), it's my inability in triggering the undocumented 83MHz bus setting for this card.

Here is theretroweb link: https://theretroweb.com/motherboards/s/octek-rhino-15-2 where the 83MHz mode is listed;
Also by visual inspection, I found that there is a PLL chip W48C67-01H, very similar to the one mounted on the FIC PA-2010 and ASUS TX97-E motherboards that support that speed setting, and they even have the correct jumper settings online!
But with my motherboard, I literally tried all permutations of jumpers for bus speed (even leaving some unpopulated) and nothing works.

Is there anyone that has used this motherboard here? Or any ideas on what more experiments I can do. They would be much appreciated.

Reply 1 of 3, by BitWrangler

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Hmmm multiple things to go over. On your default multiplier of 5 on that CPU, it is probably going to be a no POST when you set it to 83, if it doesn't work on a 3.5 or 4x multiplier, it doesn't work. If you can run at 75x5 you are doing really well.

Secondly, if the CPU is set to a lower multi and you are getting no-POSTs for 83, then a PCI card probably really doesn't like it, you have to cherry pick them.

Thirdly, if you keep trying and trying and your POST screen still says 333, well, maybe it's at 333, maybe it isn't maybe 333 is just what the BIOS guesses at when the multi set to 5, or maybe it's the highest CPU that BIOS supports, don't assume it didn't change until you run some utils/benchmarks that can detect CPU speed.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 2 of 3, by gerrokarp35

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Hi, thanks for the reply. This is my CPU:
https://www.cpu-world.com/CPUs/K6-2/AMD-K6-2% … 6-2-333AFR.html

I can POST at every combination of jumper setting I tried with a multiplier kept low at 3.5 or 3x. Never saw more than 75MHz bus. But I can run it at 75*5=375MHz no problem, seems stable. The issue are very slow access times and transfer rate for SDRAM memory (I keep it at 64MB max cached size for 430TX chipset), and in general low performance. But maybe there are other issues at play, I simply would like to see the magic 83MHz combination 😀

Reply 3 of 3, by rasz_pl

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define slow transfer rate, can you post your cachechk as is now?

gerrokarp35 wrote on 2024-10-05, 16:03:

Also by visual inspection, I found that there is a PLL chip W48C67-01H, very similar to the one mounted on the FIC PA-2010 and ASUS TX97-E

similar but not same, its same as on FIC PA-2011 and Re: Clock generators on Socket 7 and older motherboards doesnt look as 85 is there

https://github.com/raszpl/FIC-486-GAC-2-Cache-Module for AT&T Globalyst
https://github.com/raszpl/386RC-16 memory board
https://github.com/raszpl/440BX Reference Design adapted to Kicad
https://github.com/raszpl/Zenith_ZBIOS MFM-300 Monitor

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