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eed30b Bob Green 2026-03-12 09:34:11
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# Board Features
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The sbc-3 board contains the following:
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- Two banks of static ram. Each bank can take either 4x512KB AS6C4008 or (if you like soldering SMDs) 4x2MB ?????. The BIOS will autodetect the amount of memory present. Max memory possible in the two banks is therefore 16MB.
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- XR68C681 Duart. Two independent serial ports. _See the note below about the PS/2 keyboard and mouse._
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- CompactFlash interface
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- MC68230 PI/T. Provides two banks of 8-bit I/O and a timer counter, with an external 10MHz clock.
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- DS1307 Real time clock with battery backup.
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- PS/2 keyboard and mouse interfaces. If you use these, they will tie up the second port on the duart.
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3db9dd Bob Green 2026-03-12 11:22:50
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## Duart
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### Beware.
eed30b Bob Green 2026-03-12 09:34:11
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I bought a Motorola MC68681 duart and discovered that it should have been an XR68681 duart. The Motorola part is an older design and can't run at the speeds that the newer chip can. I was able to get it to run, but at 38400 instead of 230400. When you're loading large programs via the serial interface, that makes a *huge* difference, so don't be like me, get the correct chip first time.
3db9dd Bob Green 2026-03-12 11:22:50
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## PI/T
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### Links
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- [Good Example](https://people.engr.tamu.edu/rgutier/web_courses/ceg453_s00/l2.pdf) of how to program the device and handle the interrupts in C.