Jetway J433-A Socket 3 mainboard with AM5x86 \ VOGONS

Jetway J433-A Socket 3 mainboard with AM5x86

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First post, by majestyk

Posted on 2024-06-05, 07:36

majestyk Offline

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VIA chipsets are not very common for the Socket 3 platform and thy are not said to be the performance champions.
So I gave the Jetway J433-A try after finishing some (several) repairs.

The attachment J433_total1.JPG is no longer available

And here´s the jumpering for AM5x86 @ 4 x 40 MHz

The attachment J433_jmpr1.JPG is no longer available

For internal x4 multiplier you need to add the pull-down resistor at the CPU´s CLK-MUL pin

The attachment J433_wb1.JPG is no longer available

The memory performance is not actually breathtaking though...

The attachment J433_perf.JPG is no longer available

...but it´s still a solid and versatile "VIP" mainboard.

The original VRM transistor was a Darlington type (TIP117) that got roasted to death due to a non-exixtent heatsink and no thermal contact to the PCB.
I replaced it by a "regular" BJT transistor and found no problems so far.

Last edited by majestyk on 2024-06-18, 15:50. Edited 1 time in total.

Reply 1 of 3, by pyrogx

Posted on 2024-06-05, 10:53

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How's the PCI performance (and the compatibility)? I ran into a lot of issue with 486 PCI boards in the past, especially with graphics cards.

Reply 2 of 3, by quicknick

Posted on 2024-06-05, 23:25

quicknick Offline

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Nice. I have this board and I'll give it another chance using your jumper settings. I actually put a label on it, "don't mess with this until you have the manual/jumper table, it's just a waste of time". Board works, but I found the speed to be appalling, something akin to a fast 286 (with PCI/VLB bonus!) for which I have no use. For extra slowness, as if one needs it, I remember the clock generator having a 8 MHz setting...

What value is the WT/WB resistor? From the photo it seems to be a 0-ohm, but that would be too hard of a pull-down.

Reply 3 of 3, by majestyk

Posted on 2024-06-06, 05:45

majestyk Offline

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I have tested under DOS only. All my PCI video cards (ATI, Nvidia, S3, Cirrus Logic) are working fine, the clock generator has to be set to "async" in most cases when 40 MHz FSB is selected.

The WB resistor is 100R here (code 1000).

The only BIOS available on retroweb does not support Am5x86 CPUS and is a bit dated. Because there are not many mainboards with this chipset around, most of them FIC, I used the latest FIC "486 VIP-IO 2" BIOS and just disabled the onboard I/O stuff. I made myself a modded version with the unused menue entries hidden and disabled.
This FIC BIOS unfortunately lacks the detailed settings for RAM and Cache timings, so you are limited to "slow, normal, fast...". These settings are not hidden, but non exixtent in this BIOS as it seems.

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