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MAT 286 - oscillators question

archeocomp

Experienced Member
Joined
Apr 29, 2012
Messages
416
Location
EU/SK
Hi, I have this 286/1MB RAM, HT12, QUADTEL BIOS mobo (real picture).

mat286sm.jpg

Is seems to work. I've only tested it till it complains about CMOS failure. I removed the battery and cleaned the board with IPA to stop further damages.

Stason links:
https://stason.org/TULARC/pc/motherboards/U/UNIDENTIFIED-286-MAT-286-MICRO-AT-BA15D.html

https://stason.org/TULARC/pc/motherboards/U/UNIDENTIFIED-286-MAT-286.html

It has a 20MHz CPU and a 32MHz oscillator at Y2 position. I also have bought a 10MHZ 80287 form aliexpress that I want to use.

https://www.aliexpress.com/item/4001129508800.html

There are two unpopulated positions for Y3 and Y4 oscillators. I believe it runs now at 16MHZ CPU, no NPU. Stason's description of the jumper settings is incomplete and I believe wrong. What oscillators and jumper settings do I need to populate to max out the board to 20MHz CPU and 10MHz NPU performance?
 
Here I am two years later with more info on my MAT286 revision D motherboad. I desoldered the 32MHz oscillator to see what label is beneath. It says AT clock. So in a state as it is in the picture it works like this. AT bus runs at 8MHz (32/4), CPU runs at 16MHz (32/2), that is performance cca 11x original PC, NPU is unpopulated.

As you can see CPU was 20MHz Harris 286. I populated all three oscilator positions with sockets. I returned back 32MHz oscillator at AT clock position. I populated 40MHz oscillator at Main clock position, removed jumper next to AT oscillator. Now the CPU runs at 20MHz (40/2) and zero wait states. It reports speed 14x original PC.
Furthermore I populated NPU with 287-10 version and NPU oscillator with 40Mhz and NPU now runs at 10MHz (32/4), Checkit reports no frequency, but performance in the region 60x original PC.

And btw now with 40MHz Main oscillator the NPU oscillator may be left unpopulated, and clock for NPU can be taken from Main oscillator be moving jumper (jumper next to Main oscillator) to the other posistion.

There is still room for further speed improvements :) I ordered 50MHz oscillators and 25MHz Intersil 286 from China. Relatively cheap Harris 286 25MHz from eBay did not work at all.
 
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