https://github.com/matze79/PS2-Adapter

PS/2 to Microsoft Serialmouse Adapter Converter / Updated First Post / Firmware Update added

Hehe, you could have saved yourself a lot of time.

matze79 wrote on 2026-06-01, 14:40:

https://github.com/matze79/PS2-Adapter

PS/2 to Microsoft Serialmouse Adapter Converter / Updated First Post / Firmware Update added

Hehe, you could have saved yourself a lot of time.

I was aware of this project, but I wanted an internal adapter that doesn't have parts sticking out from the back of the case. 😀

maxtherabbit wrote on 2026-06-01, 14:06:

I thought there was some logitech mode which always ran at 4800 or 9600 baud anyway which most of the drivers already supported

I have never heard of it, what's that? It does sound like something that's probably not widely supported.

Also, if it requires host PC sending data to mouse, you would need a RS-232 transceiver that has more RX lines. MAX232 has just two, and they are needed for RTS and DTR lines.

Most Logitech Serial Mice Support this, Logitech Driver for Windows also.
3 Button Protocol at 1200, 2400, 4800 and 9600 Baud

The Logitech C7 also supports Autobaud Mode.
If one sends a specific ASCII character at the specific Baud, it will recognize it and switch Speed.
The C7 had superior Tracking compared to MS-Mouse

matze79 wrote on 2026-06-01, 15:10:

Most Logitech Serial Mice Support this, Logitech Driver for Windows also. 3 Button Protocol at 1200, 2400, 4800 and 9600 Baud […]
Show full quote

Most Logitech Serial Mice Support this, Logitech Driver for Windows also.
3 Button Protocol at 1200, 2400, 4800 and 9600 Baud

The Logitech C7 also supports Autobaud Mode.
If one sends a specific ASCII character at the specific Baud, it will recognize it and switch Speed.
The C7 had superior Tracking compared to MS-Mouse

Hmm, do you have more info about this? For example, does it support wheel mice? Although if you have to install specific drivers for it, you might just as well use modified drivers.

Mike_ wrote on 2026-06-01, 15:20:

matze79 wrote on 2026-06-01, 15:10:

Most Logitech Serial Mice Support this, Logitech Driver for Windows also. 3 Button Protocol at 1200, 2400, 4800 and 9600 Baud […]
Show full quote

Most Logitech Serial Mice Support this, Logitech Driver for Windows also.
3 Button Protocol at 1200, 2400, 4800 and 9600 Baud

The Logitech C7 also supports Autobaud Mode.
If one sends a specific ASCII character at the specific Baud, it will recognize it and switch Speed.
The C7 had superior Tracking compared to MS-Mouse

Hmm, do you have more info about this? For example, does it support wheel mice? Although if you have to install specific drivers for it, you might just as well use modified drivers.

it does support wheel mice, and it "just works" with cute mouse and stock windows 3.11 (thought the wheel is useless in windows 3.11)

I have not personally tested it against win9x but reports are that it just works there as well

the rio444 board implements this as default and the enhanced update rate over a normal serial mouse is immediately noticeable

maxtherabbit wrote on 2026-06-01, 23:25:

it does support wheel mice, and it "just works" with cute mouse and stock windows 3.11 (thought the wheel is useless in windows 3.11)

I have not personally tested it against win9x but reports are that it just works there as well

the rio444 board implements this as default and the enhanced update rate over a normal serial mouse is immediately noticeable

This doesn't make any sense. rio444's ISA board doesn't use *any* baud rate as it doesn't send data to a serial port to begin with. Instead it pretends to *be* a serial port and as such it can send an interrupt through ISA bus immediately when the data is available. The mouse driver, having no way of knowing that the data didn't actually chug along a 1200 baud serial line, happily goes to fetch the packet from registers. As such it doesn't matter what drivers you are using.

As far as I know, ctmouse doesn't support some "Logitech 9600 baud mode" and Windows 95 default drivers certainly don't. I was actually using an old Logitech three button serial mouse when I was setting up my 486 in winter, and the slow mouse update rate caused by 1200 baud rate was easily visible on screen. I didn't find much info about this with quick googling either, if it really was that common it shouldn't be so obscure knownledge.

Mike_ wrote on 2026-05-30, 11:02:

If I understood correctly, it now works correctly with his KVM switch.

Can confirm - The KVM quirks are now accounted for and it works flawlessly. The KVM fixes the PS/2 rate to 100Hz, probably they did that in the design to fix some issue between different devices. The reset issue is also fixed, the mouse movement is now continuous.

I used the 9600baud CuteMouse 2.0A4 for DOS and windows 98 mouse files to allow for 100 updates/sec. Without the updated drivers they would not detect a mouse. At the original 1200 baud rate the movement would be delayed and choppy through the KVM.

The issues were only apparently when using the KVM, when directly connected both USB mice and native PS/2 mice worked fine.

Mike_ wrote on 2026-06-02, 05:10:

maxtherabbit wrote on 2026-06-01, 23:25:

it does support wheel mice, and it "just works" with cute mouse and stock windows 3.11 (thought the wheel is useless in windows 3.11)

I have not personally tested it against win9x but reports are that it just works there as well

the rio444 board implements this as default and the enhanced update rate over a normal serial mouse is immediately noticeable

This doesn't make any sense. rio444's ISA board doesn't use *any* baud rate as it doesn't send data to a serial port to begin with. Instead it pretends to *be* a serial port and as such it can send an interrupt through ISA bus immediately when the data is available. The mouse driver, having no way of knowing that the data didn't actually chug along a 1200 baud serial line, happily goes to fetch the packet from registers. As such it doesn't matter what drivers you are using.

As far as I know, ctmouse doesn't support some "Logitech 9600 baud mode" and Windows 95 default drivers certainly don't. I was actually using an old Logitech three button serial mouse when I was setting up my 486 in winter, and the slow mouse update rate caused by 1200 baud rate was easily visible on screen. I didn't find much info about this with quick googling either, if it really was that common it shouldn't be so obscure knownledge.

That's a good point, it didn't occur to me that nothing is stopping the card from generating IRQs faster than the driver programs the emulated serial port.

That said, it does specifically use "logitech mode" and cute mouse reports it as such

maxtherabbit wrote on 2026-06-02, 19:55:

That's a good point, it didn't occur to me that nothing is stopping the card from generating IRQs faster than the driver programs the emulated serial port.

That said, it does specifically use "logitech mode" and cute mouse reports it as such

Yes, "normal" Logitech mode at 1200baud, or 3-button mode is widely supported, but that's not the same as the "Logitech 9600 baud mode" we are talking about. It's basically an extension that adds support for third button.

3 Button Logitech extension
Logitech extended the 2 button mouse protocol to support 3 button mice by adding a 4th byte when the middle button is pressed (and the first packet after it is released). If a 4th byte is encountered (i.e., an extra byte with D6 set to 0) then D5 of that byte (0x20) indicates the status of the middle mouse button.

https://roborooter.com/post/serial-mice/

It appears that there are some old Logitech mice that support 9600 baud rate, such as Logitech C7. Also, apparently there are some other later Logitech serial mice, such as series 9, which support 2400 baud rate. There's very little information out there about it, which makes it sound like it's not widely supported. Also, apparently that Logitech C7 also received data from host to determine baud rate, which would mean that you need at least three RX lines for RS-232 transceiver. Ie. MAX232 would not be sufficient, and you would have to use a bigger chip. That sounds like a lot hassle to implement something that's not supported in default drivers.

https://matejhorvat.si/sl/slorac/delta/partner/logimoc7.pdf