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DEC 6502 Cross-assembly

RichCini

RichCini

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All --

In a thread elsewhere in [DEC] (here: http://www.vcfed.org/forum/showthre...DP-11-or-8-be-used-when-it-was-still-relevant) dealing with historical uses for these machines, DougSnyder mentioned that Atari had used the PDP-11/20 to cross-assemble games. If you follow this trail, it indirectly leads to some stories here: http://www.jmargolin.com/vmail/vmail.htm

The thread didn't dive into it, but I thought it might be an interesting topic. So, I did a little digging and found two interesting things. First, there was a 6502 cross assembler in the DECUS archive (ASM65, DECUS# 110520), but it doesn't seem to be archived anywhere. Then, I came across this book, "A Cross-assembler for the 6502 Microprocessor, with the PDP-11 as Host Computer and the SYM-1 as the Target Microcomputer" by Khin Nyan Chu. I can't find an ISBN, nor does it seem to be archived anywhere.

I have an 11/23 in the basement and how cool would it be to re-compile an Atari 2600 game and run it on Stella...I think it would be a cool project.

Rich
 
That’s interesting. Does this code exist anywhere? I was intrigued how Gates & Allen used UUO on the PDP-10 for cross-compiling 8080 instructions, but I was never able to locate samples of how that would have been implemented. Different method, I know, but looking to learn something new :-)
 
RichCini said:
Going back to the cross-assembler, apparently there is a 6502 cross assembler on one of the DECUS tapes (#110520) called ASM65. I haven't been able to come up with it by Googling and the archive CD doesn't seem to have it. Any pointers?
Click to expand...

If I ever get proficient in PDP-11 (might just happen) I'll certainly write (port) my own. Of course, I'll probably write a cross-assembler for PDP-11 on 65xx first. And unless I suddenly find myself retired, (much less likely) don't expect anything to happen quickly.
 
Sadly much of the DECUS archive was thrown away. There are some items on Bitsavers, but this one appears lost. Cross Assemblers were pretty common place. for example, whilst it didn't have a 6502 the Mitchen Terminal System (MTS) which ran on an IBM mainframe contains cross assemblers for Intel 8080 and Motorola 6800 and 6809...
 
Dave — that loss is partially what prompted this thread. I did look at several different versions of the DECUS archive on line (bitsavers is my usual first stop) and none had this program. I just didn’t know why it wouldn’t have been there. Sad to see that holes exist in the archive, though.

Rich
 
Rich,

Well originally the DECUS library was a collection of physical media. From what I remember you paid DECUS for a copy of what you wanted which meant that no one other than DECUS had a complete library. The charges for a copy were not insignificant, so you only got a copy of what you needed, meaning not many copies exist. At some point DECUS discarded the whole caboodle and much was lost. I have no idea why they binned it, but that is why there isn't a complete on-line. Its very frustrating as a lot of interesting stuff appears lost.

I know some of the missing stuff was mounted on one of the group servers, so it might be there...

Dave
 
g4ugm said:
Rich,

I know some of the missing stuff was mounted on one of the group servers, so it might be there...

Dave
Click to expand...

There was a downloading frenzy about a month ago when they put that disk back on line at eisner.decus.org.

I pulled down a copy. It's about 3.9gb with many DECUS SIG tape images.

When I did that I read all of the remaining DECUS SIG 1/2" tapes that I still have, mostly duplicates of what
they had along with a few from DECUS Canada. I haven't had time to put those up yet.
 
Thanks! That looks like a very interesting site indeed, so I'm going to dig into it a bit more this weekend. I have the DEQNA working on my machine so I do finally have Internet access. I haven't done much with it yet beyond verifying I can access my internal FTP site though. The system is an 11/23 with 256kw of RAM (Q18). Maybe I can try text-based email with that or maybe browsing using Telnet. Open to ideas...
 
g4ugm said:
Well originally the DECUS library was a collection of physical media. From what I remember you paid DECUS for a copy of what you wanted which meant that no one other than DECUS had a complete library. The charges for a copy were not insignificant, so you only got a copy of what you needed, meaning not many copies exist. At some point DECUS discarded the whole caboodle and much was lost. I have no idea why they binned it, but that is why there isn't a complete on-line. Its very frustrating as a lot of interesting stuff appears lost.
Click to expand...
You could also get the software from the contributor directly if they were willing. The DECUS library had this mantra that "the only charges are for the media and the labor to create the copies", yet you could spend a lot of money ($100 for a 9-track tape? Really?) so people only bought things they knew they could use. The cost discouraged buying things on the chance that they might be useful. I caused quite a fuss about the library charges which led to some price reductions. I don't know if they were counting kilobytes as feet of paper tape and using the same pricing metric into the magtape era or what the deal was.

I believe the SIG Tapes were at least partially in response to DECUS Library pricing - people contributed software, volunteers organized and cataloged it, and passed it down a "reverse pyramid" where people would make copies and send them to more people who would then do the same, and so on.

When NADGUG (the North American Data General User's Group) folded, they sent all the members unsolicited magtapes with everything the library ever held.
 
One the general topic of cross assemblers hosted on DEC machines, there was a suite of cross assemblers targeting various microprocessors that was available from a company called "Boston Systems Office" back in the early 1980's.
The company that I worked for at the time used their 6809 cross assembler on a PDP-11 running V7 UNIX - I believe that they also had versions that ran under VMS.
 
We used the BSO Z80 cross-assembler on a PDP-11 running RSX-11/M+.

SDL also had an 8086 cross-assembler that we used as well. Found a bug in it last year... Had to produce a work-around after all this time...

Dave
 
There was a raft of cross-assemblers written in FORTRAN to be (relatively) platform-independent (I wrote a couple myself). You might count those as well.
 
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