DOS ain't dead

Hi,
this is pure HW question but may be interesting for other DOS users. I assume that you, like me prefer native PS/2 connection for KB+mouse because of buggy BIOS USB legacy support. Now I'm going to upgrade to LGA1155 platform where I want to have DOS installation too. The problem is that most of MBs have only single PS/2 connector that is mentioned to use KB OR Mouse but not both. Some users reported that thery tried Y-split adapter working on older MB but it doesn't work on newer (tested on Gigabyte MB).
My question is that it can be splitted by differently wired adapter or if it requires some HW mod to MB?
I looked that SuperIO chip on MB have 2 separate PS/2 lines for KB and mouse. So I guess there's some "intelligent" switch circuit that route one or other line from superIO to PS/2 port. It have to probe what is plugged in and then switch right way - how does it? I think it would be possible to blow off this circuit and tap directly to super IO but I'm afraid if BIOS wouldn't interfere some way (it's autodetection routine). Did somebody solved this problem?
Unfortunatelly LGA1155 MBs vanished from PC-shops so I have limited choice what other users will sell. Also I need must-have feature: COM+LPT port and >=PCI slots. So it may not be easy to buy MB with such lucky combination and 2 native PS/2...

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DOS gives me freedom to unlimited HW access.

You can split a PS/2 connection.

> You can
> split
> a PS/2 connection.

Sure, but some users on various forums reported, that this splitters didn't work for them on some Gigabyte MBs. But today one colleague Frank assured me that in his case Y-splitter worked on MB GA-B85M-D3H rev.2.0. So I'm confused if Gigabyte is manufacturing two different combined PS/2 that one is crippled and other works. But how to recognize them?

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DOS gives me freedom to unlimited HW access.

To use a Y-splitter, the motherboard hardware/BIOS must be designed correctly, and it sounds like on at least some of the modern Gigabyte boards (and maybe those from other manufacturers as well) this isn't the case. There's probably nothing you can do to fix it. Your most viable option is probably to use a USB mouse and a PS2 keyboard.

BTW, it's a similar situation for the PS2-to-USB adapters that are supposed to let you plug a USB mouse/keyboard into a PS2 port. Those are simply wiring adapters and assume the mouse hardware is capable of understanding both PS2 and USB protocols (which are VERY different from each other). Such "dual-mode" mice (and sometimes keyboards) were relatively common back in the early days of USB when PS2 was just starting to be phased out, but not any more. And you can't tell which are which just by looking at them -- you need to find the design specs.

> To use a Y-splitter, the motherboard hardware/BIOS must be designed
> correctly, and it sounds like on at least some of the modern Gigabyte
> boards (and maybe those from other manufacturers as well) this isn't the
> case. There's probably nothing you can do to fix it. Your most viable
> option is probably to use a USB mouse and a PS2 keyboard.

In case of Frank's MB he reported me that the pinout of combined PS/2 simply use the unused pins to populate mouse PS/2 signals. So his Y-splitter simply wires this pins correctly to female connector for mouse and no problem. In such case there's no need BIOS do anything. But I don't know if there exist some different combined PS/2 pinout. I can imagine it would physically use only 4 pins like normal PS/2 and switch data signals. I would need some MB to probe with DMM or a schematics...

> BTW, it's a similar situation for the PS2-to-USB adapters that are supposed
> to let you plug a USB mouse/keyboard into a PS2 port. Those are simply
> wiring adapters and assume the mouse hardware is capable of understanding
> both PS2 and USB protocols (which are VERY different from each other).
> Such "dual-mode" mice (and sometimes keyboards) were relatively common back
> in the early days of USB when PS2 was just starting to be phased out, but
> not any more. And you can't tell which are which just by looking at them
> -- you need to find the design specs.

Yes, I already use MS intelli explorer USB via this adapter. I never disassembled it so I'm a little bit surprised now. But I remember that I read somewhere, that the adapter works only with MS mices, so this makes sense...

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DOS gives me freedom to unlimited HW access.

> Yes, I already use MS intelli explorer USB via this adapter. I never
> disassembled it so I'm a little bit surprised now. But I remember that I
> read somewhere, that the adapter works only with MS mices, so this makes
> sense...

I'd be surprised if that were true that it only works with MS mice. I believe that I used splitter for a couple years before USB took over, and the first USB mouse I bought was also my first MS mouse.

> I'd be surprised if that were true that it only works with MS mice. I
> believe that I used splitter for a couple years before USB took over, and
> the first USB mouse I bought was also my first MS mouse.

In this case I didn' mean the splitter but USB to PS/2 adapter. Like Bret told that not every mouse supports dual protocol...

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DOS gives me freedom to unlimited HW access.

> > I'd be surprised if that were true that it only works with MS mice. I
> > believe that I used splitter for a couple years before USB took over,
> and
> > the first USB mouse I bought was also my first MS mouse.
>
> In this case I didn' mean the splitter but USB to PS/2 adapter. Like Bret
> told that not every mouse supports dual protocol...

I have the same problem, so I asked my friend, electronics engineer, to
explain all details to me.

If the mouse has its USB to PS/2 adaptor in the package, it can support
both protocols, because it has onboard adaptor IC built in. He told me that
there are several ICs of that type. Onboard IC does all the job, so there
is no need for any software to do the conversion.
If the mouse does not have USB to PS/2 adaptor, you can disasemble the mouse
to inspect the board and see if it has the converter IC or you can
attach the adaptor and try it.

Sorry, I do not have the list of converter ICs.

Maybe this will help.

I have only MS IntelliMouse Explorer and Optical where MS seems to be generous to provide USB-PS/2 adapter to most of his mice.

OK, and could he also tell something to combined PS/2 at 6x chipset GB MBs? :)

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DOS gives me freedom to unlimited HW access.

> I have only MS IntelliMouse Explorer and Optical where MS seems to be
> generous to provide USB-PS/2 adapter to most of his mice.
>
> OK, and could he also tell something to combined PS/2 at 6x chipset GB MBs?
> :)

He can, but I can also.
I have an older GB mainboard. All such boards have the same problem:
When GigaByte started to implement FireWire, all USB versions, and SATA,
they needed more memory for BIOS. Instead of buying bigger memory chip
they decided to save some money. So they deleted all what they considered
obsolete, and I have BIOS problem, not hardware one.
The results of such stupid saving are for my GB motherboard:
There are two serial ports, but BIOS supports only one, and there is no
serial mouse support, only external modem works.
I have standard IDE controller with only two ports, but only master is
supported (BIOS does not see slave IDE).
Diskette controller is also standard, but only A is working. Another
diskette can be connected, but it is not supported. I can only use standard
media with 80 tracks and 15 or 18 sectors, BIOS does not see other
diskette formats, so HD-COPY for DOS is useless.

Most newer MBs are even worse. The producers remove all hardware they
consider obsolete, not only BIOS code.

Hm, this seems really crippled. What model and chipset exactly is it?
My current Gigabyte MB GA-P31-DS3L (LGA775, intel P31) have quite good BIOS support. I don't have any floppy od IDE limitation, even uide driver works here. I have yet an old-style textmode Award BIOS. But newer LGA1155 MBs mostly using UEFI. Some years ago I have shortly borrowed one MB GA-B75M-D3V with UEFI and I didn't find fatal error with DOS. It also supported EDD 3.0. Here are some logs. Unfortunatelly I didn't tried the PS/2 for both KB+mouse as I belived it must work with Y-cable. If I remember well, there was issues with Win98 that booted only in safemode and dos-based setup crashed so unable to make a new install.

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DOS gives me freedom to unlimited HW access.

> Hm, this seems really crippled. What model and chipset exactly is it?
> My current Gigabyte MB GA-P31-DS3L (LGA775, intel P31) have quite good BIOS
> support. I don't have any floppy od IDE limitation, even uide driver works
> here. I have yet an old-style textmode Award BIOS. But newer LGA1155 MBs
> mostly using UEFI. Some years ago I have shortly borrowed one MB
> GA-B75M-D3V with UEFI and I didn't find fatal error with DOS. It also
> supported EDD 3.0. Here are some
> logs. Unfortunatelly I
> didn't tried the PS/2 for both KB+mouse as I belived it must work with
> Y-cable. If I remember well, there was issues with Win98 that booted only
> in safemode and dos-based setup crashed so unable to make a new install.

I have GB MA770T-UD3 with Award 6.0 Rev1 BIOS. Some people got flash update
for that crippled BIOS, but it is not available anymore.
Its AMD chipset supports AMD Phenom with 4 cores. BTW, I use SATA for disks
and it works perfectly. DVD is on IDE channel and UIDE from 05.03.2015 works
also. If I get combo diskette unit I could use two diskettes.
Both PS/2 ports work also.

I tested one MB with updated BIOS. Serial mouse works and two IDE ports are
supported. There is still only one diskette supported, but all formats
work, even 5 inch formatted as 1.44 MB.

Back to topic. I got one Gigabyte GA-P67-DS3-B3 MB and checked PS/2 connector with DMM. Unfortunately it seems like pins 2 and 6 on left side are not connected. Neither resistance nor diode test could indicate some silicon or circuit there. So there must be some switching logic to route proper PS/2 line from superIO to the same pins 1 and 5. Next I measured that there is resistance about 83ohm from superIO KCLK and KDATA to PS/2 pins 1 and 5. They are not connected with MCLK and MDATA. I cannot find where MCLK and MDATA are routed. I'll try to lift this pins up from the pads and wire them to another PS/2 port but currently I don't have any DDR3 module to run the MB.
Crippled gigaidiots...

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DOS gives me freedom to unlimited HW access.

I got DDR3 module to run the MB and tried how the PS/2 port works. I used USB bootdisk with freeDOS and ctmouse. When I boot with KB plugged it worked as expected. So I put ctmouse and DN to autoexec, plug mouse to PS/2 and reboot. Mouse worked too. What's interesting, when I swap mouse by KB during dos session the KB was properly initialized and worked without reboot. When I swap back to mouse it didn't work, probably would need ctmouse run again... So it seems there some swithing logic that is activated whenever something is plugged in even on runtime not only boot up.
Now I plan to connect mouse to superIO directly and see what will happen...

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DOS gives me freedom to unlimited HW access.

Well, I made it - the HW mod. I tapped superIO mouse line to second PS/2 connector that I glued on MB and did proper wiring + damping and pull up resistors. Fortunatelly BIOS is capable to handle this change and now I can use my KB and mouse simultaneously :) Even more interesting is that It doesn't matter where I plug KB and mouse, BIOS always detect it correctly and swiych the function. Also during running system I can swap it.

http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod1.jpg
http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod2.jpg
http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod3.jpg

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DOS gives me freedom to unlimited HW access.

> Well, I made it - the HW mod. I tapped superIO mouse line to second PS/2
> connector that I glued on MB and did proper wiring + damping and pull up
> resistors. Fortunatelly BIOS is capable to handle this change and now I can
> use my KB and mouse simultaneously :) Even more interesting is that It
> doesn't matter where I plug KB and mouse, BIOS always detect it correctly
> and swiych the function. Also during running system I can swap it.
>
> http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod1.jpg
> http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod2.jpg
> http://rayer.g6.cz/1tmp/GA-P67-DS3-B3/mod3.jpg

I love your ESD workbench and liner. Surprised it took a hardware mod to get the functionality you were looking for.

> I love your ESD workbench and liner. Surprised it took a hardware mod
> to get the functionality you were looking for.

Hehe, another more complex thing to try would be use of TPM header to connect a DIY PCB with some LPC superIO that supports floppy controller. Even it would be possible to connect Fintek LPC to ISA bridge (like some industrial MB with ISA does onboard). Just an idea, if I'll have some time to play with it... There are already some TPM gadgets like this POST card: https://www.pugetsystems.com/images/pic_disp.php?id=20569&width=800&height=800

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DOS gives me freedom to unlimited HW access.