That’s a bus mouse. We’d have to have a look at the rest of the device to tell you more.

Oh ok! Never heard of that. Here is the rest of the mouse. No PC included sadly...

It's a Microsoft InPort mouse.

Is the sticker still on its belly? If so, are texts on it readable?

Nope, no sticker. It looks like the end user can open the mouse by design though...

Are these mice special or interesting or something?

Almoststew1990 wrote on 2021-08-01, 21:41:

Nope, no sticker. It looks like the end user can open the mouse by design though...

That was pretty normal in the olden days because the rollers needed a clean once in a while. All ACORN Risc systems use that type of mouse connector up until the A7000s.

Almoststew1990 wrote on 2021-08-01, 21:41:

Are these mice special or interesting or something?

They are rather uncommon nowadays, at least.
Some old PCs from the 8086 or 80286/80386 days have a bus mouse interface on the motherboard.
So by using a bus mouse, the on-board serial port can be used for other tasks.

Bus mouse interfaces do need an interrupt, though, if memory serves.
So a bus mouse may slow down a PC a bit in comparison to an RS232 mouse.
Or something like that. I'm sorry, my knowledge about bus mice is a bit limited, I'm afraid.

Anyone know whether bus mice were cheaper than serial mice?
That's the main reason I can see for them...

These mice were the standard for Japanese PC-98 computers. My 286 PC has a Microsoft InPort card in it, and I don't have the official Microsoft mouse for it, but the Japanese mouse I got with my PC-98 works fine on it.

jakethompson1 wrote on 2021-08-01, 22:22:

Anyone know whether bus mice were cheaper than serial mice?
That's the main reason I can see for them...

Serial mice had terrible CPU overhead. Bus mouse introduced a dedicated controller to lessen the need for the CPU interrupts for every sample.

Another thing about bus mouse, no IC in it. Just direct connections to sensors and switches.

I didn't thought about less CPU overhead. Is there?

Cheers,

Jo22 wrote on 2021-08-01, 22:04:

They are rather uncommon nowadays, at least. Some old PCs from the 8086 or 80286/80386 days have a bus mouse interface on the […]
Show full quote

Almoststew1990 wrote on 2021-08-01, 21:41:

Are these mice special or interesting or something?

They are rather uncommon nowadays, at least.
Some old PCs from the 8086 or 80286/80386 days have a bus mouse interface on the motherboard.
So by using a bus mouse, the on-board serial port can be used for other tasks.

Bus mouse interfaces do need an interrupt, though, if memory serves.
So a bus mouse may slow down a PC a bit in comparison to an RS232 mouse.
Or something like that. I'm sorry, my knowledge about bus mice is a bit limited, I'm afraid.

Ah? Serial mice take up irqs as well.

pentiumspeed wrote on 2021-08-01, 23:09:

Another thing about bus mouse, no IC in it. Just direct connections to sensors and switches.

I didn't thought about less CPU overhead. Is there?

Cheers,

There is no notable difference between using a bus or serial port mouse as far as the end user is concerned.

Caluser2000 wrote on 2021-08-02, 00:17:

Jo22 wrote on 2021-08-01, 22:04:

They are rather uncommon nowadays, at least. Some old PCs from the 8086 or 80286/80386 days have a bus mouse interface on the […]
Show full quote

Almoststew1990 wrote on 2021-08-01, 21:41:

Are these mice special or interesting or something?

They are rather uncommon nowadays, at least.
Some old PCs from the 8086 or 80286/80386 days have a bus mouse interface on the motherboard.
So by using a bus mouse, the on-board serial port can be used for other tasks.

Bus mouse interfaces do need an interrupt, though, if memory serves.
So a bus mouse may slow down a PC a bit in comparison to an RS232 mouse.
Or something like that. I'm sorry, my knowledge about bus mice is a bit limited, I'm afraid.

Ah? Serial mice take up irqs as well.

I guess that's true, though the bus mouse interfaces always (?) used the 8250 chip and the serial port did not?

https://en.wikipedia.org/wiki/Bus_mouse#Further_reading

That 8250 chip is considered slow and buggy nowadays.
It was replaced by the 16450 and 16550A, which are used in ATs.
The latter has a big buffer (FiFo) , too and does use the IRQ line way less often.
(There's a Windows 3.1 setting in system.ini for 16550)

The MS Mouse 9 driver also causes less overhead?
And bus mice can't use it, since they use Mouse Systems protocol? 😕

Edit: I'm speaking under correction here. Have to check. Unfortunately, there's a lots of stress in real life right now. 🙁

Edit: That system.ini setting may have been "FiFo=1" or "FiFo=true", not sure.
Anyway, the 16550A seems pin compatible with the 16450.
If you have a 286/386, consider adding a socket to your ISA multi-i/o card or ISA seriall/parallel card.
The 16550A might be useful for null modem connections etc.

Here's some mouse stuff that I remember from my past. Maybe they contain some useful information or links that are useful.
They are not free from errors, maybe, so please double check.
Also, the other users did write neat stuff, too. It's just..
I'm having trouble with concentration right now, I'm sorry. Maybe I take a break for a while. 🙁

Re: My childhood Peacock 8MHz XT

Re: 8BIT ISA SERIAL I/O TO PS2 MOUSE

Tiny mouse driver ?

Re: RS232

PS: I wonder, maybe the MS InPort cards can be upgraded with a 16550A?
Maybe a daughterboard can be made in case it's not pin compatible with 8250?
That would be cool. Because, during power up, they all pretend to be a 8250 chip.

Windows for Workgroups 3.11 comes with a new serial port driver than can do higher baud rates (9600 +) just fine.
That CyberCom driver may work with 286 PCs, though.

Jo22 wrote on 2021-08-02, 14:33:

PS: I wonder, maybe the MS InPort cards can be upgraded with a 16550A?

The UARTs 8250 and 16550A are for serial communication. The InPort mouse doesn't use serial communication at all, and I have no evidence that the original InPort card contains an UART at all.

You can find the pinout of the InPort mouse at https://deskthority.net/wiki/Bus_mouse#Microsoft_InPort . It shows that the cable from the mouse to the computer contains the raw sensor and button signals, not a serial data stream (as serial mice would). The counter that counts the pulses of the rotary encoders in the mouse is in the one chip on the microsoft InPort card, and the counter values can be directly read over the ISA bus, with no serial data stream in between.

The interrupt rate of a serial MS mouse is higher than the interrupt rate of a bus mouse: A serial mouse sends around 150 bytes / second, and every byte triggers an interrupt. Three bytes make a packet, so you get up to 50 updates / second. If the bochs emulation of the bus mouse is true to the original hardware and emulates a MS InPort-compatible card, only 30 interrupts / second are generated, and an update is available on every interrupt. The process of reading data from the bus port chip seems to need more I/O cycles than reading the serial data from an MS mouse.

So my verdict is: If the IRQ processsing overhead is the main limiting factor, the bus mouse is the clear winner (only 1/5th of the IRQ rate compared to serial mice). On the other hand, if ISA 8-bit cycles are the main limiting factor, the serial mouse might win out. The latter might be the case on fast x86 systems (high end 486, Pentium) without a memory manager like EMM386. On the other hand, I think the whole discussion is academic, because the real CPU load (at least in graphics modes) isn't caused by the communication protocol, but from re-drawing the mouse cursor. Redrawing the mouse cursor takes the same effort no matter how the position has been received. If serial MS mice make use of the technically possible 50 updates per second, and the driver redraws the cursor with every position update, the CPU load will be higher than with a bus mouse that only posts 30 updates per second to the mouse driver. If the mouse cursor is drawn in the main loop of the application at the screen refresh rate of the application instead of the update rate of the mouse, the mouse port type likely makes no difference at all.

16550 is replaceable with no changes for eariler UART IC.

Cheers,