Late 486 MB - PCI450-A looking for the infromation \ VOGONS

Late 486 MB - PCI450-A looking for the infromation

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First post, by Susanin79

Posted on 2024-09-02, 21:33

Susanin79 Offline

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Greetings,
Recently bought this nice late 486 motherboard with PCI and VLB cards support and looking for the Jumper settings. For this moment system works stable only with the Cyrix DX40 CPU without L2 cache installed. Hopefully major settings were silk-screened at the board. Will try to eliminate the CPU power related jumpers.
For now I did the Jumpers drawing and mark the initial jumpers position on it. Most of the Jumpers except JF1, JF2, JF3 are clearly marked, only these has no pin 1 mark.
Will be appreciated if somebody will recognize this MB or the jumpers combination and let me know.
For this moment the closest MB is: https://theretroweb.com/motherboards/s/protech-pm486pa-vip but the jumpers didn't match.
Will post my experiments update here.
BIOS image attached to this thread.

1TRW BIOS analyze (!b):
2__________________________________________________________
3File:     PCI450-A.BIN
4Vendor:   Phoenix
5Version:  4.03
6String:   
7Sign-on:  
8Metadata: [Build] devel028
9                  05/17/94 16:39:17
10          [ID] PhoenixBIOS Version 4.03  
11               Copyright 1987-1993 Phoenix Technologies Ltd., All Rights Reserved.
12          [SCSI] NCR 3.0
13          [Table] ACER M1429 (System)
14ROMs: [1000:0003] Broadcom/LSI 53c825

Reply 1 of 4, by dominusprog

Posted on 2024-09-02, 22:08

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Can't help with jumpers, but you should remove the battery immediately. Also add a little bit of thermal paste and screw the voltage regulator to the board.

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Reply 2 of 4, by Horun

Posted on 2024-09-03, 03:23

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Hmm it uses a KTS KDN-0147C timer, is pin compatible with certain ICS AV9107C-#. Looking at back of board and the JF1,2,3 jumpers I see some square pads which could signify pin 1 when compared to other side of board like with jx3 with square pad on pin 1 (and a few others) -> I would guess the square pad signifies pin 1. That is not conclusive but a fair guess. It appears your board is somewhat a clone or diff revision of that Protech board. Sorry is all I have on quick look.
Added: you might want to check ohms to ground and +5 on some of the other square pads for jumpers labeled 1 and see if it matches with Jf jumpers, that also could help using a datasheet for the timer....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 4, by Susanin79

Posted on 2024-09-03, 20:32

Susanin79 Offline

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dominusprog wrote on 2024-09-02, 22:08:

Can't help with jumpers, but you should remove the battery immediately. Also add a little bit of thermal paste and screw the voltage regulator to the board.

Already ordered a small heat sink, this voltage regulator and mosfet were replaced earlier as well as some tantalum capacitors. Battery works and didn't leak, so probably it was replaced too. But I will remove it anyway after the experiments.

Reply 4 of 4, by Susanin79

Posted on 2024-09-03, 20:38

Susanin79 Offline

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Horun wrote on 2024-09-03, 03:23:

Hmm it uses a KTS KDN-0147C timer, is pin compatible with certain ICS AV9107C-#. Looking at back of board and the JF1,2,3 jumpers I see some square pads which could signify pin 1 when compared to other side of board like with jx3 with square pad on pin 1 (and a few others) -> I would guess the square pad signifies pin 1. That is not conclusive but a fair guess. It appears your board is somewhat a clone or diff revision of that Protech board. Sorry is all I have on quick look.
Added: you might want to check ohms to ground and +5 on some of the other square pads for jumpers labeled 1 and see if it matches with Jf jumpers, that also could help using a datasheet for the timer....

Thanks so much! It works, the square pads deferentially pointed to the pin1, as soon as I set the JF jumpers correct, I was able to run my 486 DX4 overdrive CPU. L1 cache works well now.
Now time to play with the L2 cache jumpers. Previously they were set to 512KB, but the 32Kx8 dirty tag IC didn't fit it.

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