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Microsoft green-eyed mouse (serial version) connector gender?

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robert_smallshire

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Nov 11, 2025
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I'm aware that the earliest (1983) Microsoft green-eyed mouse came in (at least) two versions:

A Bus Mouse version which used a male DE-9 connector (albeit with pins 1 and 7 omitted) on the mouse cable. This version required a special PC/XT ISA card to provide the interface and was described by Microsoft as "for the IBM PC that either doesn't have a serial communications interface board installed or whose serial communications port is already used for something else". The signals from the mouse were raw quadrature from the encoders.

microsoft-mouse-v1-paul-g-allen.png
The second version was a Serial Mouse which used a female DB-25 connector on the mouse cable for use with a standard (at the time) RS-232 port with a male connector on the PC. The Microsoft documentation says, "Serial version packages include the mouse pointing unit, a connecting cable, and a 25-pin female connector."microsoft-mouse-v1-db-25-serial.jpg
Sadly, there is so much confusion about early mouse connectors, and so many sellers inadvertently mislabelling that it's relatively difficult to find reliable information. Much of the confusion is caused by misidentification of the DE-9 bus mouse connector as a 9-pin serial connector. Of course, eventually DE-9 mouse connectors did eventually became common, but for serial mice, and with female gender on the mouse cable. Microsoft eventually retired DE-9 male bus mouse connector in favour of the Mini-DIN-9 InPort connector and interface board in 1986.

Having finally got this picture clear in my head, my understanding of the story has been confounded by finding pictures of green-eyed mouses with DB-25 *male* connectors.
Screenshot 2025-11-27 at 20.06.59.png
CEv77lPWMAAru_B.jpeg

This is a real surprise, not consistent with the documentation, and not consistent with PC serial ports having male gender. At first I thought the connectors may have been changed, but all the examples I've found have Microsoft-branded DB-25 male connectors, although some only have the necessary pins, not the full complement of 25.

What's the story here? Are these aftermarket modifications, or different product versions or product revisions?
 
Presumably it was sourcing. One batch they were shipping connectors with just five pins. On another batch they bought connectors with all 25 pins included even if they were not needed.
 
Perhaps, but switching from the documented female DB-25 to male DB-25 with however many pins is a big change given that serial ports on the computer had male connectors. I'd be surprised if a change in gender was just a sourcing decision.
 
Some early clones used female serial connectors. My Columbia Data Products and Eagle PC computers use female DB-25 connectors for the serial port on the back of the machines. I have to use a gender changer to connect them to normal serial mice.

Those two Microsoft mice look like they would work perfectly on these computers, no adapter needed.

I was under the impression it was more common to use female serial connectors on the back of computers (a bit harder to damage) until the IBM PC came along, and had to differentiate from their parallel port. (My Eagle PC uses a Centronix connector for parallel, and the Columbia Data Products uses some other larger connector)
 
I seem to remember that some of the MS green eyed mouse designs plugged into an intermediate box instead of directly to the computer. I can't find an image to verify though.
 
krebizfan said:
I seem to remember that some of the MS green eyed mouse designs plugged into an intermediate box instead of directly to the computer. I can't find an image to verify though.
Click to expand...
Are you confusing them with the early Mouse Systems optical mice? They were serial, but they had a separate power supply and an intermediate box they plugged into before connecting to the computer.
 
From an RS-232 standard perspective (yes, I know that doesn't count for much) the computer is the DTE (Data Terminal Equipment) and should have a male connector, and the mouse is the DCE (Data Communication Equipment) and so should have a female connector. This is supported by the fact that data from the mouse to computer is sent over the RxD line, consistent with DTE transmitting on TxD and receiving on the RxD line. So if there is a "proper" gender arrangement it is male on the computer and female on the mouse, as per the Microsoft documentation.

Another possibility is that the plastic connector shells we see in the pictures with the male mouse connectors are original, but that the actual D-sub connectors themselves have been swapped out for male versions in order to be compatible with some early non-standard serial interface.
 
If this helps, here's a picture of both "green eyed" Microsoft mice. The 25 pin serial DB-25 version on the left and the DE9 bus version on the right with the matching Microsoft ISA bus mouse card it connects to on top.


Microsoft Green Eyed Mice sm.JPG
 
@snuci If these are your green-eyed mice: Can you you be so kind as to answer a few of questions? 1) Does the serial mouse have a female or male connector? 2) Assuming the DE-9 connector on the bus mouse has only 7 pins, does the female connector on the ISA card have 9 holes or 7 holes for mechanical keying? None of the photos I've found of the connector-side of the card are good enough to make this clear. 3) May I use your picture with attribution in a forthcoming blog post about the green-eyed mouse variants?
 
The serial mouse has a male connector. The female connector on the bus card has 9 pins populated and all are connected to the card. Here is a picture with the back side of the card. All pins are connected except one on the back and the one missing is connected on the front side.

Feel free to use these pictures. Hope this helps.

Microsoft green eyed mouse bus card - rear sm.jpg
 
robert_smallshire said:
The Microsoft documentation says, "Serial version packages include the mouse pointing unit, a connecting cable, and a 25-pin female connector."
Click to expand...
I wonder if "a 25-pin female connector" refers to an included adapter?

Two other points:
The mini-DIN is afaik 8-pin. I don't even think 9-pin mini-DIN is an actual standardized connector. (There are a bunch of non-standard mini-DIN like connectors, where some is slightly larger than standard mini-DIN connectors. These seems to be somewhat common for breakout adapters for graphics cards with various TV/component/whatnot inputs/outputs, and are also found on various other things like for example the 80's/90's Volvo car stereos that have Volvos proprietary version of the Alpine CD changer connector (IIRC called M-bus)).

The reason for having a male connector on the 9-pin bus mouse, and a female connector on the computer, is to avoid short circuiting the power rail if you insert the connector with power turned on. Compare with mice and joysticks using the Atari joystick pinout. All joysticks lack a metal shield for the DE-9 female connector, as that shield would short circuit +5 to ground if you insert the connector with power turned on and ever so slightly miss align the connector.

A tangent: In hindsight this product has a strong Microsoft aura in that they didn't really care about what "other not really related but also not totally unrelated" products did. In particular it would had been great if they had used the Atari DE-9 joystick pinout and just had opted for using left/right for the horizontal signals, and up/down as the vertical signals. If they had done so, then we would likely had ended up with the same pinout for mice on the Amiga and the Atari ST. (They are very similar, but the quadrature signals use different pins...).
SomeGuy said:
Some early clones used female serial connectors. My Columbia Data Products and Eagle PC computers use female DB-25 connectors for the serial port on the back of the machines. I have to use a gender changer to connect them to normal serial mice.

Those two Microsoft mice look like they would work perfectly on these computers, no adapter needed.

I was under the impression it was more common to use female serial connectors on the back of computers (a bit harder to damage) until the IBM PC came along, and had to differentiate from their parallel port. (My Eagle PC uses a Centronix connector for parallel, and the Columbia Data Products uses some other larger connector)
Click to expand...
This is a good point.
The gender of DB25 connectors seems to have been kind of hit and miss before the PC standard became dominant enough. As a comparison, as late as in 1985 the Amiga 1000 had opposite genders for the serial and parallel port as compared to a PC. Later on with the A2000 and A500 they switched to the same gender as PCs and a mostly compatible pinout. (There are some non-PC signals, like power rails via resistors and whatnot, on pins that are rarely used anyways).
 
@MiaM I don’t want to get too far on to the topic of the bus mouse as this thread is about the gender of the serial mouse connectors. Save to say that the Microsoft bus mouse did indeed use a Mini-DIN-9 connector which superseded their use of the DE-9 connector. This was branded InPort, also required a custom ISA card, and is described on the Wikipedia page. https://en.wikipedia.org/wiki/Bus_mouse
 
@MiaM On the bus mouse power rail short circuiting theory, yours is an interesting hypothesis, but in fact there is no power rail on the Microsoft bus mouse DE-9 (7) connector. The mouse uses mechanical closed-contact encoders rather than optoelectronic encoders like later mice, so is entirely passive. The signal lines are pulled high by resistors on the interface board and pulled low by switch activations in the mouse, so it’s all active-low logic.
 
@snuci Any chance of a clear picture of the back of the bus mouse card with the female DE-9 connector? There are currently no clear pictures of this anywhere on the web, so far as I can tell, so it would be a useful contribution!
 
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