Some day before i bought mobo for Socket 3 CPU.
I want to put 486 DX4 that have 3.3 core voltage to check it.
But i can't find manual for this mobo to understand which CPU's and voltahes it's support.
I understand that it is a something IBM PC 300 series. But this information gives nothing.
I put photo below so may be some one can help me.
See that black connector in the far left bottom corner with the shunt jumper block in it? It needs a VRM to get 3.3V So without one of those you're restricted to 5V
Machine type would be a 6571 I think , looks very similar to one I just picked up.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
All the settings, beep codes and memory configs are in here, http://ps-2.kev009.com/basil.holloway/boo-to- … 83G_7789_08.pdf but it covers the whole model range so make sure you're looking at the right section.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
BitWrangler wrote on 2021-10-05, 18:05:All the settings, beep codes and memory configs are in here, http://ps-2.kev009.com/basil.holloway/boo-to- … 83G_7789_08.pdf but it covers the whole model range so make sure you're looking at the right section.
At first. I thank you for reply.
This manual gave me some brain food.
Frist mention about this board at page 219 with schematic representation.
There are such strings :
PC 330/350 Series (Type 657X, 658X) - 80486 System Board
+------------------------------------------------------------------------+
¦ Processor ¦ J23 ¦ J24 ¦
+-----------------------+------------------------+-----------------------¦
¦ 486SX (D) ¦ 1-2 ¦ Open ¦
+-----------------------+------------------------+-----------------------¦
¦ 486DX ¦ 2-3 ¦ Open ¦
+-----------------------+------------------------+-----------------------¦
¦ P24T ¦ 2-3 ¦ Closed ¦
+------------------------------------------------------------------------+
And ,
CPU Speed Selection
+------------------------------------------------------------------------+
¦ Speed ¦ J35 ¦ J36 ¦ J37 ¦
+-----------------+------------------+-----------------+-----------------¦
¦ 20 MHz ¦ On ¦ Off ¦ Off ¦
+-----------------+------------------+-----------------+-----------------¦
¦ 25 MHz (D) ¦ Off ¦ On ¦ On ¦
+-----------------+------------------+-----------------+-----------------¦
¦ 33 MHz ¦ Off ¦ On ¦ Off ¦
+-----------------+------------------+-----------------+-----------------¦
¦ 40 MHz ¦ Off ¦ Off ¦ On ¦
+-----------------+------------------+-----------------+-----------------¦
¦ 50 MHz ¦ Off ¦ Off ¦ Off ¦
+------------------------------------------------------------------------+
Clocks multiple selections is noted only for p24t ( 486overdrive) with such strings:
P24 Clock Selection
+------------------------------------------------------------------------+
¦ JP10 ¦ 1-2 ¦ 3-4 ¦
+-----------------------+------------------------+-----------------------¦
¦ Internal Clock ¦ Off ¦ Off ¦
¦ - X3 (D) ¦ ¦ ¦
+-----------------------+------------------------+-----------------------¦
¦ Internal Clock ¦ Off ¦ On ¦
¦ - X2 ¦ ¦ ¦
+-----------------------+------------------------+-----------------------¦
¦ Other ¦ On ¦ Off ¦
¦ Multiplier ¦ ¦ ¦
+------------------------------------------------------------------------+
After some research i made sure that all CPU's in list have 5V core voltage.
Based on this, I have the opinion that the voltage on this motherboard is fixed at 5V.
The only thing that confuses me string in manual about :
12 Processor Regulator Connector( looks like combined jumpers.. i'll post photo of it below.
And second thing that first owner use this board with 486DX2 (unfortunately was sold).
ApostolCV wrote on 2021-10-06, 21:36:After some research i made sure that all CPU's in list have 5V core voltage. Based on this, I have the opinion that the voltage […]
After some research i made sure that all CPU's in list have 5V core voltage.
Based on this, I have the opinion that the voltage on this motherboard is fixed at 5V.
The only thing that confuses me string in manual about :
12 Processor Regulator Connector( looks like combined jumpers.. i'll post photo of it below.
And second thing that first owner use this board with 486DX2 (unfortunately was sold).
Similar to a Pentium VRM socket. When some pins are jumped it supplies the proper NON-VRM voltage (5v in your case, 3.3v on Pentiums).
Those jumpers are removed when a Proper VRM module is installed to supply other CPU voltages.
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
ApostolCV is your lucky day, and a little bit mine too ... I have the same mainboard as you (actually I have the whole computer) but ... the DX4 version !! then with the original IBM voltage regulator installed at the factory. I am attaching some photos, in my opinion it is not at all a difficult circuit to reproduce, if you are interested we can deepen it. What I see, however, that you have (and what I lack) is that jumper block you installed where I have the regulator. I would need to know how they are configured because when I install a 486 at 5v I always feed it at 3.3.
https://drive.google.com/drive/folders/1-KiNs … y3W?usp=sharing
AlessandroB, it's really great to find man with the same mobo.
If i am right it's good for you. From my own observation this jumpers on my mobo act as a bridge. They connect 5V rail from PSU to CPU (logical 😉.
So in your case you just need enough of jumpers.😀
But for me it's a little harder. I need to know the denominations of capacitors and diode.
At worse i'll buy Intel486DX2 for this mobo (for DX4 i have other working motherboard).
But, we don't search easy ways.😁
Go to see in the folder of the photos, I have added some with the values of the components
If you could find a DX4 ODPR (Overdrive Replacement), they run on 5V
Why? it cost more than the full computer, regulator is really easy to build
I guess you'll need something similar to this ....
Right to repair is fundamental. You own it, you're allowed to fix it.
How To Ask Questions The Smart Way
Do not ask Why !
https://www.vogonswiki.com/index.php/Serial_port
Weedeewee thx for answers.
Looks like i can buy Premium overdrive DX40DPR100.
Would this be the best solution?
