80287 FPU - Asynchronous Clock Board \ VOGONS

80287 FPU - Asynchronous Clock Board

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First post, by matze79

Posted on 2022-10-14, 10:40

matze79 Offline

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Joined: 2014-12-12, 14:25
Location: Germany, Frankonia

New Project:

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80287 Clock Board.

it allows to clock 287 FPU at different Clockrate.
For Example to run 6Mhz 286 with 20Mhz FPU.

Not yet tested 😀
i will order it after moving on 5.11

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 1 of 3, by Jo22

Posted on 2022-10-14, 13:08

Jo22 Offline

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Cool! 😎👍

Um, if I'm allowed to make an advice..
Maybe the crystal oscillator can be buffered, for an even cleaner TTL signal.

Because, I had issues myself with a modded Mega Drive..
My 68010 isn't exactly stable with the separate clock. Another user fixed this issue with an HD74LS14, I think.
That's why it came to mind.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 2 of 3, by matze79

Posted on 2022-10-14, 18:05

matze79 Offline

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Rank: l33t
Posts: 2974
Joined: 2014-12-12, 14:25
Location: Germany, Frankonia

Its buffered trough the 4bit Counter, i think this should suffice.
But it seems like i can omit the counter.. and instead use a oscillator directly.
Then maybe a single buffer gate would be enough.

Madao checked his Adapter.
And it does not care about the 287 datasheet and 33% Duty Cycle and its working.

Data:

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https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

Reply 3 of 3, by matze79

Posted on 2022-11-21, 08:54

matze79 Offline

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Rank: l33t
Posts: 2974
Joined: 2014-12-12, 14:25
Location: Germany, Frankonia

Proud Test Canidates arrived!

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More Pictures from Madao:

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so 50:50 Duty Cycle will suit all 287 well.

https://www.retrokits.de - blog, retro projects, hdd clicker, diy soundcards etc
https://www.retroianer.de - german retro computer board

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