I just checked it; R56 is 1500 Ohms.

Thank you for your quick help. Using a 1500 ohms resistor with JP23 bridged gives a somewhat low output voltage around 3.15 V. Maybe the used components have disadvantageous tolerances. Replacing it with a 2200 ohm part gives a sufficient 3.35 V output.

Sorry to up the thread but after reading interestingly I think I made a bad mod on the very same mainboard. As I bought it I immediately changed the battery (I discover now it was rechargable) and installed a new three cell 3.6v Ni-Mh 80Mah BM704-33. I have not boot the mainboard yet missing some components, but will I destroy the battery as power going to it will charge it? I don't think this battery is rechargable...

I also bought a "three cell 3.6v NiMh" for this board, A bigger 600mAh pack. The original barrel battery marked 'GP60BNKX3' was a NiCad.
I found this in an ebay add:

A motherboard uses only a very, very low and steady trickle charge current which is just high enough to maintain the battery in a fully charged state, but not high enough to overcharge. Trickle chargers are very simple designs and do not detect anything. NiCd and NiMH batteries are interchangeable for use with trickle chargers such as used in motherboards.

Actually the 486 worked fine for months on 3 AA Alkaline batteries connected to JP1.
http://www.batterymart.com/c-battery-facts-faqs.html:

In most cases, replacement of the CMOS battery is an easy task. It is simply a matter of locating the battery on the computer's motherboard, removing it and plugging in a new one. As a rule, internal batteries should be replaced by the same type of battery which was originally used in the machine or according to the manufacturers specifications. The major exception to this rule are older PCs which were manufactured with a NiCad battery soldered onto the motherboard. These computers usually have a three or four pin male plug, with two of the pins connected via a jumper (this is generally found in the same area of the motherboard as the original battery). This plug gives you the option of leaving the soldered battery in place and replacing it with a plug-in lithium or alkaline battery. Removing the jumper tells the computer to ignore the soldered battery and to look to the pins for its power source. If the motherboard has this provision, you can install a standard PC plug-in battery instead of removing the soldered battery and re-soldering a new one (the standard PC plug-in battery is Electro Battery part number BAT 2005 (lithium) or BAT B40 (alkaline). These batteries are interchangeable).

Well I read this too late... I pointed now the positive side of the ni-mh battery on the first pin of JP1 as seen in this thread leaving the jumper on 2-3. So the positive hole on the original position battery is now empty. Is it right, isn't it?

What I understand from the quoted text: The original barrel battery connector is trickle charged, suitable for NiCd or NiMH, whilst the use of JP1 will not charge a connected battery. So one can connect any battery to JP1; it will work, but the battery will run empty.

IIRC it does not matter if you use the negative terminal from the barrel battery or 'JP1 pin 4', as they are the same line.

(Am unable to verify, this system is in storage.)

Past week I rearranged the storage attic. I took a better look at the yellowed keyboard belonging to this 486, and surprisingly it is actually a quality item: A Cherry G80-1000 HDU /05:

deskthority: "G80-1000 HDU (US layout, black switches, N-key rollover, beige |\ key)"

The black switches are probably of the 'Vintage' type. De keycaps are 'doubleshot'. Must try this myself, as I only used rubber dome keyboards up to this point.

Also had a look at the monitor. It is a Hansol 710A; nothing special I suppose.

This board make me crazy. It has no regulator so 5v only cpu on it. I tried my Overdrive DX4-100 16WT and set up everything as P24C on 33Mhz bus in it and booting up it hang after ram count also reporting the cpu as DX4-S 120Mhz !
33Mhz x 3, how can it feel a 120Mhz cpu that never existed. Tried different cpu but don't seems to be stable at boot sometime it run sometimes it hang. Motheboard is perfect, no traces broken or anthing.

I will soon get one of these boards so I will see what kind of CPUs I can get running.

I have an AMD 5x86-133p75 I could try as its an Evergreen 5V model. 😀

386SX wrote:

Tried different cpu but don't seems to be stable at boot sometime it run sometimes it hang.

Are you saying that you haven't found a single CPU to run reliable so far? In that case I would try a simple intel 486DX-33 first.

My board worked fine with an Am486DX4-100SV8B. Even before updating the BIOS.

Well, it seems that probably is related to my VLB controller ide/floppy card. I am not sure cause I don't have any spare working card to replace and other two I had can't even see anything on the ide cable.
But I begin to suspect it that card.

Here is my board, it seems I have the VRM so I guess I can run 3.3V CPUs without hassle! 😀

My board seems to work fine but the battery diddnt look very nice so I removed it.

BastlerMike wrote:

Bios-wise I am now using an AMI Winbios designed for the PC Chips M912. A big advantage is that you can use EDO memory.

I was thinking of this EDO memory remark of yours. It sounds interesting. Are you still around to elaborate a little: Where is this BIOS? Does it require one to select EDO/FPM in the BIOS. Does it take all kinds of 5 Volt EDO modules? Does it bench faster then a system with FPM memory?

Many bios files available here: http://www.elhvb.com/mobokive/Archive/index.html
No user configurable options needed, it simply works. No speed difference observable.

Got it, thanks!

Curious if the 1995 Award BIOS (UM498F!.ZIP) I mentioned is also EDO memory compatible. But since there is no speed benefit, there is little reason to obtain some of that EDO memory to try.

In a way I find the currently installed 16MB FPM set the most fitting for a 486 VLB system. Though 32MB would be nice for Windows 95. Then again I rarely run windows on this system.

There were a few changes to this system last week:

Replaced the GD5428 graphics card with a ... GD5428 graphics card. This one occupies less space inside the case and has SMD components. Also I noticed it has no visual glitches in mode-X, unlike the previous one. It came without the optional video memory, neither did it have the latest BIOS, so I took those from the previous card. What is still a little annoying is that the Windows "1024x768 60Hz hi-color" mode does not sync with my old TFT monitor, but 256 color mode does.

When mounted on the VLB I/O card, The IDE to SD-Card adapter was obstructing ISA slots. So I made a IDE 90-degree angle bracket.

Got an ISA Ethernet card from 1997. In case I ever feel the need to connect this 486 to a network. It did not install properly in Windows 95 in the first try though. It started behaving better in DOS after disabling its ISA-PnP-mode with a 3COM tool. Still have to retry the Windows 95 installation in this Non-PnP-mode.

Finally, I removed the CMI8330 sound card and tried the Acer Magic S23 (CS4232) again. This time it worked flawless! Maybe the newer BIOS made the difference? I am very satisfied with the combination Acer Magic S23 + Terratec/Dream 4MB Midi daughterboard. My Slot 1 VIA C3 system has the same combo. Maybe a GUS PnP (Interwave) would add some additional 16-bit compatibility, but I don't have a spare one for this system.

How's the compatibility with the Magic S23?

Sound Blaster Pro and Windows Sound System. The usual shared setup where WSS has the same IRQ/DMA and Mixer as the SBPro. SBPro compatibility is solid, so is WSS. FM and MPU-401 work well too. Windows 9x drivers are nice and simple, with proper DosBox sound support.

• Some things to consider:
• It is a PnP card, and I found it hard to get it on IRQ 7 unless I use the Resource.exe tool, to adjust the PnP info header of the card.
• Tyrian expects WSS to be on the the classic DMA 0 and IRQ 5 IIRC, no way to configure. This game gives WSS a bad rep.
• Allegro-Library based DOS games with SBPro at 22kHz do not work properly with it. They need their exe patched so that the value for 45454 (Hz) becomes 43478 (Hz), then they work fine.
• Unlike the Sound Blaster the WSS should be unmuted when starting a game, then muted at exit. Nice idea to get 100% silence. But games often don't mute at exit. MPXplay does not unmute the WSS at startup, unless you pass the -scv 100 parameter. In SBPro mode this is of no concern.
• When closing some games, they leave the card in a state where the WSS-mode sampling rate or DMA buffer is messed up. This can be fixed using my homebrew CSreset tool.
• Acer Magic S23 was also sold as Philips PCA70PS.

Sorry to update the thread but I got the same mainboard and I can't find an award flasher version that works. All the one tells me that "it's not the new award bios version, please update bios version first (???)" or "the file part doesn't match the system ....". Are there any specific version for this mobo?

For this 486 I hotflashed the EEPROM with a newer Pentium II motherboard. But preferably use a Programmer Device.