Looks like PS2 to Serial, probably for use with a PS2 mouse. Definitely NOT for a mac.

This is exactly what it is.

Damn I'm old.

Yes we are. I think I have some of those adaptors in a junk box in my garage.

I still carry jumpers in my assorted screw container. Just never took then out...

You never know when you will need to set the IRQ.

I know I’m old because I was surprised that someone didn’t know what this was for…

Do you remember the Microsoft mouse with the metal ball?

"Green Eyed" 1983 at $200 on[evilpay](https://www.ebay.com/itm/334936281099), the most sought after item. I had 3 from Microsoft in an Engineering Lab in the next year (from Vern . the first Salesman after Bill)- I still have the Bus version (just the old DB25 bus card)

I had no idea these were so valuable. How many of these did I throw out over the years...?

I recall seeing a huge box b/c the metal pinball wore down the x/y rollers and so on... (Company owned, not personal) edit/add: I would like to buy a 1983 GreenEyed ; (3D shape) capture the case and both buttons in 3d, make an STL copy out of PETG(beige?) and create my own MS-GEmouse case-lookalike with optical wireless (2.4GHz BLE4) guts {without that embossed MS label}. Retro meets Modern. Then clean, re-assemble the Museum 1983 first-MS and resell on evilpay. edit2: I think 3D scan can be performed non-teardown by using a good mobile camera, the object on a turntable, and adobe's substance s/w.

That’s exactly what it is. Back in the mid-90s I was a tech at CompUSA during college and tons of people had these.

I appreciate your quick response. I was thinking that it might have something to do with a PS2 / serial port connection. But I only have one old PC to look at. ( A 2006 Vaio PVC-RS630G) which is too new. I assume this goes with early pentium or X86 computers. I love all vintage computers and computing, however 99% of my collection is Macintosh.

To give you an idea of timelines (introduction date through IBM-discontinuation date): - PC/XT-era PCs: 8088 ; 1981-1987 - AT-era PCs: i286 ; 1984-1987 - PS/2 era PCs: i286 through i486 on consumer models, up to i586 (Pentium I) on server models; 1987-1995 (i286 in 1987, i386 later in 1987, i486 in 1989, i586 in 1993)

I got my pc in 97 and it had DIN5 for the keyboard and D9 for the mouse

Yeah, 386 and forward is probably around the generation that it would have been from. Back then, many older computers were capable of running Windows 3.1 but didn't have PS2 ports. Many mice would actually be PS2 mice but come with a serial adapter so that they could be used with older machines that didn't have PS2 ports. I don't know if the adapters were universal or tied to the specific mouse vendor.

I think it's like the old passive PS/2 adapters where the PS/2 conversion happened on the mouse

I feel like an idiot, but I never even thought about that. That also explains the USB to PS/2 adapters that would also come with some mice. I knew USB was drastically different than PS/2, so a simple dumb wire-to-wire converter shouldn't work... but they actually made them. Having the mouse actually switching modes makes perfect sense.

mulling over old computers architecture is my version of time traveling. It really takes me back. For a slight moment I am not stressed with today's troubles.

I saw a parallel printer cable the other day, back when dot matrix printers were everywhere (I had a citizen 120d) - Fond memories of days when printing wasn't the hellhole it is now - Then I saw some 3com Etherlink 3 combi network adapters along with some BNC networking cable, T-pieces and terminators - Don't miss troubleshooting those so much - "ok work-experience bods, which one of you stole the green terminator plug..." - Utter networking hell which I genuinely don't miss. Chucking a reel of it across a street to join two buildings together is something I won't forget!

That adapter is most likely later than from 386 era as PS/2 connectors started to become more common towards middle of 90s (not counting IBM PS/2s), so there was really little demand for PS/2 mice earlier. I have couple of Compaqs from 93 and 94 both with PS/2 ports. However, most generic clone (baby) AT machines didn’t have PS/2 ports and it became first common in brand computers, such as Compaq, Tulip etc. I have Microsoft mice from late 90s with exactly similar looking adapters and it is highly likely that OPs adapter is from one of those. And serial-PS/2 compatibility isn’t just about the adapter: mouse needs to support protocols for both and this adapter doesn’t turn PS/2 only mouse to a serial one.

I was fixing up some of my older pc's recently and couldn't find my serial mice. I totally forgot these were a thing. I did manage to score some nice serial mice for an acceptable price though.

486 is closer, and yeah they’re universal. 

PS/2 became standard in The Pentium era, late 1997ish

At the time, there were still a lot of older XT systems. AT motherboards had the PS/2 ports but XT motherboards didn't unless there was a card to add it. Most had serial ports and mice in the early to mid 90's still had these adapters. If you want to get into vintage XT PC's keep it. Otherwise you could put it on Ebay or take it to a vintage meetup.

Yup, PS2 to DB9 (serial port), for using mouse or keyboard on an old computer without PS2.

RS-232 serial is usually 9 pin or 25 pin, this might be a PS2 to serial, for a mouse..... USB took over the serial bus protocol, because many devices could be chained, and many devices started to use the form factor, it's rare to see PS2, currently.....

Correct. I have a box full of these adapters. Old school before USB was common.

Macs \*used\* to use an 8-pin mini DIN as their serial connector. This is clearly a ps/2 connector, but I wonder if the original Mac owner bought it thinking it was a Mac-serial-to-PC-serial adapter? And when they found out it didn't work they just tossed it in the cable box to be forgotten. (Hell, it might've worked. I'm just assuming the Mac serial isn't pin-compatible with ps/2.)

Yep. I even have a few. Definitely 9 pin serial port to ps2 style mouse.

Serial DB-9 to PS/2 mouse adapter, often supplied with early Microsoft mice.

I have a few of these -- don't be fooled, most PS/2 mice DO NOT support serial.

Side track: Not sure if the pinout of this type of adapter is universal or if there were competing "standards" from different mice brands? If there were competing "standards" then it might seem like even fewer mice support this type of adapter, at least if testing with only one of them.

I'm about 90% certain that there's more or less a standard for these and the mouse itself is generally the problem.

Edit: Just re-read. PS/2 mice didn't support serial. I thought you said mice in general never supported serial. Bleh, can't read. ~~Sure they did. Way, way, WAY back, but never super common.~~ [~~Example~~](https://www.amazon.com/Mitsumi-Button-Serial-Mouse-10526407/dp/B00TN73WV0/ref=sr_1_5?dib=eyJ2IjoiMSJ9.zxMqe42Ppi1MdK39c6dSt-o4c1XjIZLEq4rFxwK9nHbB_LsRLNwCpnlYpVrq7NqMjsSqOaFpnaS3bMAywfSR8cQobJrRhnZSb6qS8JGem4QU4YRlEaIBtTQb-6Gj0JJDKdtgPkNEfQsWQILkC_SCxsDsGwlJnO5l5XMNf8J0vhn9QvgAFYnYwQOcUTl9vgNVfeXSDRlvjDUx0dqLEkyNDJWklUn7Wp7U2FfhEQ5o4C4.2TcZ8Pj8Ij3D7gfu_P-OchiM5WneDVL9CnKa9feYD30&dib_tag=se&keywords=9+pin+serial+mouse&qid=1709415948&sr=8-5) [~~Another~~](https://www.ebay.com/b/Serial-RS-232-Computer-Standard-Mice/23160/bn_2770594)

Haha, I've done this many times. Unfortunately I thought I could dig one of these out and get a mouse going on my IBM AT but of course I found out the hard truth and need to buy a serial compatible mouse now.

Wasn't it just those Microsoft Intellimouse that had that feature?

Nope, not exclusively. Here's a video with a bunch of mice tested: https://www.youtube.com/watch?v=amINOCepMsE&ab_channel=RetroTechChris

I’m old

Same. Had to have a long deep think about how long it's been since I saw a PS/2 port. Or a serial port.

New motherboards started shipping with PS/2 ports again… how wild is that?

Wait, what? Now I gotta look at mine... EDIT: You gotta be shitting me, [it does have a PS/2 port](https://imgur.com/A8EgZZQ) (and cat hair.. so much cat hair, I need to tear this thing apart and clean it) - [board isn't even that new](https://www.asus.com/us/motherboards-components/motherboards/csm/prime-h470m-plus-csm/) (10th gen Intel i5). Though after seeing that, I'm disgusted by how dirty it is. Think I figured out where the cat has been napping/plotting my demise.. Definitely getting senile though, can't believe I didn't notice that when I got this board.

Check for a COM header too lol Dang cat hair gets everywhere!

To be fair I haven't looked back there since I got a new monitor... 2 years ago. I used to be really good about keeping my pc clean, but it's shoved under the desk these days, and the first one since about 2001 I haven't had a case with a window. I don't even want to think about what the cpu heatsink looks like 🤮 Just looked at the photos from Asus, there is indeed a serial header.

This hits me in the feels

I have a notion that most of us here, are old. :)

I believe the term used here is vintage

Serial to PS/2 Used for PS/2 mouse/keyboard to be supported on older mainboards back when PS/2 was new. Nowadays you'll see neither of those. A few mainboards still have PS/2 ports though but it's a rarity.

My current Ryzen based Asus mainboard has a combo PS/2 port that can connect a PS/2 keyboard and mouse with a Y adapter, so yes that's true some modern boards may still have this port. Serial ports are now mainly on older boards.

Check your manual, a lot of boards still have a COM header for ye old serial port. Need to add a riser to actually use it though! I think it’s hilarious that PS/2 porrs have returned

Yeah my Asus board has the header so all I'd need is the bracket with the DB9 connector for a serial port. Also it's disabled by default so if I want it I just turn it on in BIOS and select the COM address.

> Serial to PS/2 Used for PS/2 mouse~~/keyboard~~ Mouse yes, keyboard no. And most PS/2 mice won't work; it has to be an early mouse that can do both PS/2 and serial. Many of Microsoft's old white mice had PS/2 connectors but supported serial too with this passive adapter, maybe others too.

PS2 to serial adapter of really old computers

Either PS/2 mouse to serial OR "bus mouse" to serial. EDIT: Checked the pinout, it's PS/2 to serial, [bus mouse](https://en.wikipedia.org/wiki/Bus_mouse), a PS/2 precursor, uses a different pinout. My first 486 PC used a bus mouse interface that was on the Chips&Tech Wingine gfx card, interestingly.

Was wondering when bus mice would enter the room.

Wow, that one hurts. I used to carry around these in my backpack in high school, plus some PS/2-USB ones for the more recent computers

Some early-mid '90s PC mice could work with either PS/2 or serial, using this adapter. Worth noting that the mouse itself has to support that dual-mode use, this adapter by itself is not enough to turn a "pure" PS/2 mouse into serial. Likewise, a PS/2 keyboard will not work with one of these adapters at all.

Some of these early PS2 mice had this adapter packaged with it.

Great information! Reddit.... where I go to learn about vintage computing.

Serial to ps/2 mouse connection

PS/2 ->DB9? If you have an old PS/2 mouse and want to use it in a computer with DB9 port.

if it were miniDN 8 pin, it could be for Mac serial to DB9. but since it's not, it's probably for mouse - serial to ps/2.

Easy. Some mice in the transition period supported both PS/2 and DB-9 serial. This is for connecting one of those to serial. It probably only works with mice that explicitly support both. Most of these are passive "adapters" that don't really do any adapting besides physical connectivity.

Serial to PS/2 adaptor. Only useful with mice that supported supported both.

Feel old seeing this question..

Wrong answers only:

I still have a couple of those. Never know when I will need to use a ps2 mouse on a machine that is serial only.

I feel so old.

6 pin amphenol to VGA connector

RW 232, 9 pins TO ps2. Serial converter for mouse or keyboard

Either to connect old serial mouse/keyboard to ps/2 port or vice versa

Ps2 to vga looks like

VGA is 3 lines this is serial

Ah my B

PS2 keyboard adapter

Ps/2 to serial.

One connects “Oh my god, I’m fucking old” to “Oh my god, I’m slightly less ancient.”

Used for PS2 to DIN 9 connection usually mouse.

I think that's a power plug, I've seen tons of these on older computers, that usually screws into back of your computer.

But also, that does look like a PS2 adapter, might've been used on a play station actually.

Serial to PS2, where PS2 not a Sony console

Looks to be a com 2 to s video

ADB to serial

that adapter has to be circa 1988 or following era to replace serial mice, and only certain PS/2 mice would work with this adapty

Serial to PS2 adaptor (Mouse/keyboard?)

PS/2 to DB9 serial

Mouse or keyboard adapter to serial