| Small 68020 [message #10809] |
Tue, 02 July 2024 09:29 |
norwestrzh
Messages: 196
Registered: November 2015
|
Senior Member |
|
|
Here is a small footprint 68020. It is similar to the 68000 that I described on Retrobrew earlier. It has 2 MB SRAM, 64k EEPROM, 68681 DUART (2 serial ports, one is the console @ 38,400), and a compact flash interface via an 82C55. I have tried a number of CPUs (16 MHz, 25 MHz, and 33 MHz) and can't get it to run at more than 25 MHz. A *real* Motorola 16 MHz "gold top" runs fine at 25 MHz, so that's what I'm using. Probably something that I don't understand about 68020 bus timing (I think it is quite different from the 68000 timing). I didn't want to tangle with dynamic bus sizing, so it is locked to an 8-bit data bus. It runs CP/M 68K with sixteen "disk drives" on the compact flash. In spite of the 8-bit data bus, performance is still very good.
Roger
-
Attachment: my68020.jpg
(Size: 753.49KB, Downloaded 116 times)
|
|
|
|
RetroBrew Computers Forum
Members
Search
Help
Login
Home
