VOGONS

80287 speed and CPU

Topic actions

First post, by theelf

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

Hi, greetings

I have a Harris 286 25mhz, zuda td60c

https://theretroweb.com/motherboards/s/zida-td60c

I found very cheap 80287 10mhz fpu on ebay, but i dont know if will work, or is tied to cpu speed

i remember i had a 10mhz fpu on a 16mhz 286 but the difference is much more here

In on of pictures in theretroweb i can see a 10mhz fpu but better ask and confirm

thanks

Reply 1 of 3, by Matth79

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

The key is JP2, EXCK and the oscillator beside it, up to the edge of the board selects separate clock, otherwise it is tied (JP2 down), looks like its a 2x clock like the CPU, oh, and in the picture, that would be clocking it at 12MHz, not 10

Reply 2 of 3, by theelf

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie
Matth79 wrote on 2025-06-22, 20:00:

The key is JP2, EXCK and the oscillator beside it, up to the edge of the board selects separate clock, otherwise it is tied (JP2 down), looks like its a 2x clock like the CPU, oh, and in the picture, that would be clocking it at 12MHz, not 10

Hi thanks for reply, this is my board, the one without external clock

the crystal in the 2x is 14.3

The attachment td60c-front-621d03777579e611109476.jpg is no longer available

Reply 3 of 3, by Matth79

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

Install osc or socket in that position (you could probably get 12MHz out of it, so you'd want a choice of 20 and 24 osc or the variable Atheatos Any_clk) and move the jumper up, as it stands, its locked to CPU, and check around that barrel battery, that could be a corrosion time bomb unless that's a new replacement.

PS. also looks like you are missing the BIOS

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window