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Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116724 01/13/20 05:40 PM
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Al Kossow Offline
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Here is the original 1983 bus mouse with the external quadrature decoder (same one as used in the Mindset)
http://bitsavers.org/pdf/microsoft/bus_mouse/1983busmouse.jpg

Last edited by Al Kossow; 01/13/20 05:40 PM.
Re: PC/XT/AT (inside) WIP topic [Re: Al Kossow] #116726 01/13/20 06:21 PM
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Lord Nightmare Offline
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Al: Is the '7801' chip on that original, pre-mcu, pre-round-connector bus mouse card a PROM? I see it is socketed, and couldn't immediately identify it, so I wonder...


"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"
Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116727 01/13/20 06:45 PM
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R. Belmont Online Content
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It's hard to tell from the photo due to parallax what the traces from the 7801 go to on the 8255, but that would probably (alongside knowledge of how you access a bus mouse from software) tell us what it is.

Re: PC/XT/AT (inside) WIP topic [Re: Lord Nightmare] #116728 01/13/20 07:03 PM
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Al Kossow Offline
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Originally Posted by Lord Nightmare
Al: Is the '7801' chip on that original, pre-mcu, pre-round-connector bus mouse card a PROM?


nope, that's the quadrature decoder

so that should give you a big hint what is inside the 40 pin asic

Re: PC/XT/AT (inside) WIP topic [Re: R. Belmont] #116729 01/13/20 07:04 PM
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Al Kossow Offline
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Originally Posted by R. Belmont
It's hard to tell from the photo due to parallax what the traces from the 7801 go to on the 8255, but that would probably (alongside knowledge of how you access a bus mouse from software) tell us what it is.


I'll go to the lab and do a high res scan of the top and bottom of the board

--done uploaded to bitsavers

Last edited by Al Kossow; 01/13/20 07:15 PM.
Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116730 01/13/20 07:07 PM
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Edstrom Offline
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So presumably a lot of that circuitry went into the custom ASIC on Rev E, that is helpful, thx!

Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116731 01/13/20 07:19 PM
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Yeah, the ASIC is just a reduced-parts-count version of what we see on the Rev D. probably.

Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116732 01/13/20 09:42 PM
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Edstrom Offline
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Interesting, the rev D screen print says "15, 30, 60, 120" and the following article says quote "And thanks to the InPort chip, the Microsoft Bus Mouse can be programmed for 30-, 50-, 100-, or 200-Hz operation. " so it seems there are differences between the revs. It appears the rate refers to how often changes interrupts the CPU and as the article explains it is possible to poll the board at even higher frequencies or hook into a vsync interrupt to adjust the cursor between frames. Great scan Al, it has all I need.

Last edited by Edstrom; 01/13/20 09:44 PM.
Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116733 01/13/20 09:49 PM
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Lord Nightmare Offline
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Edstrom: can you take a picture of the underside of that microsoft bus mouse card? I want to make sure the MCU is what I think it is.


"When life gives you zombies... *CHA-CHIK!* ...you make zombie-ade!"
Re: PC/XT/AT (inside) WIP topic [Re: Kale] #116734 01/13/20 10:02 PM
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Of course I did smile
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