Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!philabs!seismo!hao!hplabs!sri-unix!Mkb@CMU-CS-C.ARPA From: Mkb@CMU-CS-C.ARPA Newsgroups: net.micro Subject: Building a 68000 system Message-ID: <14615@sri-arpa.UUCP> Date: Thu, 15-Dec-83 05:24:00 EST Article-I.D.: sri-arpa.14615 Posted: Thu Dec 15 05:24:00 1983 Date-Received: Mon, 19-Dec-83 00:19:56 EST Lines: 44 From: Mike Blackwell Thanks to everybody who responded to my query on building a budget 68000 system! My faith in the net is restored... For those who asked, I'll summarize what I've found out: The Compupro 68000 board has sockets for two 2764's, but does not come with any ROM monitor (unless you buy their CPM, in which case you get some bootstrap ROM's). My first order of business will be to modify one of my 68000 monitors for this board (I've written a couple of monitors for our in house 68000 single board computers). The monitor contains the standard monitor features... examining and modifying memory, running with break points, etc, plus allows the downloading of MACSBUG format files over one of the serial ports. If I come up with something good, I'll make it available to net land. On the subject of Compupro's ROM sockets, whoever designed the board was exceedingly clever, and made it so that you can only read from the onboard ROM with PC relative memory reads. This makes it fairly difficult to read data constants from ROM. The trick seems to be to first run a hack routine that uses PC relative reads to copy all of your data down into RAM, where you can access it normally. Bleah. I think the reason for this misfeature is that they tried to save a few bytes of address space by mapping the onboard ROM into the same space as the IO page. Thus data reads and writes go to the IO page, and PC relative reads go to the ROM. What fun! The general consensus is that 64K bytes of memory is not enough to do anything serious. 256K seems to be the suggested minimum for a decent 68000 system. The general consensus also is that I will probably get sick of downloading files real quick, and I will break down and buy disk drives and an operating system sooner than I planned... We'll have to see on that one. It all depends on how my budget works out. For those of you who are interested, I do all of my 68000 development work on a Vax running Unix with Stanford's C cross-compiler and assembler. I've found that it works quite well (except for floating point). Anyway, in a month or so I should have everything together and hopefully running. Then I can fill you in on all the gory details! cheers, -m-