pcrow Posted July 3 Share Posted July 3 I like playing around with various versions of DOS. I was thinking of tweaking DOS 1 to address a bug or two. Did source listings ever come out for that? I've made a first pass as disassembling it, but having the original comments would make it vastly easier to make sense of. If not, then I should continue to work on making sense of the listings and make them available for anyone else also interested. The code amounts to the boot sector (128 bytes) at $0700 and 8000 bytes of DOS.SYS loaded immediately after it at $0780. [No wonder they marketed the 810 for the 800 and not the 400, as you couldn't even boot DOS 1 on an 8K 400.] 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted July 3 Share Posted July 3 DUP was published here: https://archive.org/details/ataridiskutilities/page/n1/mode/2up But I don't know about FMS/DOS. 2 Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 4 Author Share Posted July 4 I found a bug from the listings! On page 10 of the PDF at address 1778, there's a BNE instruction to optionally skip over a JSR instruction. The coder decided instead of defining a label for the target, they just used an offset from the current address: *+3. But that's three bytes from the start of the BNE instruction, not 3 bytes after the instruction, so it will branch past the JSR opcode into the target address. By sheer luck, that hits a C2 byte which is not a documented opcode, but happens to be a two-byte NOP. So on a regular 6502, the code will execute as intended. If other changes in the code shift the addresses, it will break badly. I believe it's still a 2-byte NOP on the 65C02. On the 65816, it's the REP instruction, also two bytes, and should also have no bad effects. So it's harmless, but using *+n in a branch target needs to include the two bytes of the branch instruction itself. Meanwhile I'm generating a text file version of the listings, and obviously I'm up to page 10. I'm using the results of my disassembly to save a ton of typing, which is working well, especially considering that it's often hard to read the old scans. 5 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted July 4 Share Posted July 4 Remember DOS 2 and 2.5 sources are out there as well to help with anything. And I wonder if there is a tool to scan PDFs to do OCR, or do we have to print and re-scan? I wonder if we could ask some AI tool to covert it for us. 😄 Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 4 Author Share Posted July 4 1 minute ago, kheller2 said: Remember DOS 2 and 2.5 sources are out there as well to help with anything. Was DOS 2 a complete rewrite, or was it based on the DOS 1 code? I was under the impression they were from different contractors. I suppose looking at the code would answer that. (I have the DOS 2 listings as published by COMPUTE! in my attic; I should pull it out.) 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted July 5 Share Posted July 5 As mentioned here: 1 and 2 are Paul Laughton, and you can get some of that background from the first chapter of Inside Atari DOS. Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 5 Author Share Posted July 5 Awesome! I'm going to be taking a break for a few weeks, but I'll try to get some sensible listings out eventually. Quote Link to comment Share on other sites More sharing options...
sup8pdct Posted July 9 Share Posted July 9 I saw that branch instruction noted above. I have done a dissembly and can see some routines are the same, some altered and some totally new. I am puzzled with what $25BB to $25FF is for. Unfortunately, the listing on archive for that part is missing. Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted July 9 Share Posted July 9 3 hours ago, sup8pdct said: I saw that branch instruction noted above. I have done a dissembly and can see some routines are the same, some altered and some totally new. I am puzzled with what $25BB to $25FF is for. Unfortunately, the listing on archive for that part is missing. Isn’t it at the top of page 42? 80 bytes for file spec and EOPEN routine. Quote Link to comment Share on other sites More sharing options...
sup8pdct Posted July 9 Share Posted July 9 yep. Need to put in my eyes for the 50+ year service and clean...... Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 24 Author Share Posted July 24 I've gone through the listing PDF from above, and converted my disassembly into the same format. The PDF is a bit fuzzy, so I'm sure I misread it at points, so some labels may be wrong (though probably consistent). There is only one macro, "HILO," which takes a 16-bit label and creates H and L labels for the high and low bytes of the address (for loading pointers into A and X for subroutines or into other pointers like in IOCBs). The listings expanded the macros, so most of the time I did, too (though not at the end when I got lazy). I've added comments in [square brackets] where I thought it appropriate. I put in a ^L where there's a page break in the listings file to make it easier to compare. I would like to assemble this and compare with my DOS.SYS file, but I'm not sure what assembler to use. If there's a cross-assembler that's compatible on Linux, that would be awesome. Otherwise I'm guessing I should try the Atari Macro Assembler. I know the Assembler Editor cartridge doesn't do macros, but otherwise that might work as well (and it's what I started with originally). At some point I should put this in my GitHub Atari stuff, but I want to also do the DOS portion. Then I may want to put out some patches, because that was one of the points of all this. I want to verify that it assembles first. One interesting thing I found was that my DOS.SYS file has an extra 146 zeros at the end. I expect there's a bug where the file is Another interesting point is the listings have one difference: Two instructions down from the GETFIL label, it has "LDA #10" but my disassembly has "LDA #$0B" instead. I think this is the maximum number of characters to read for a file spec, so there may have been an off-by-one error when using a drive number, such as: D1:ABCD1234.EXT dos1dup_source.asm 5 Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 26 Author Share Posted July 26 I've cleaned it up to correct inconsistent labels and a few other typos. I haven't found an assembler that matches the syntax, but with some hacks (piping the source through sed for some substitutions), it will assemble without errors. Now I need to look for binary differences to find any other errors, but it should be close. dos1dup_source.asm 5 Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 28 Author Share Posted July 28 I managed to assemble it. I hacked it up with sed (Unix tool for regular expression search/replace and such), and was able to get xa to assemble it. I then did a hexdump of the result along with a hexdump of the same portion of a DOS 1 binary I have (starting at $1300), and there were a ton of differences. Working through them, I found several typos, and with those corrected, it now is a perfect match except for variables that are zero (uninitialized) when assembling, but have whatever was in memory when written back out by DOS. It would be a little interesting to find an original factory DOS 1 disk and see if those variables are zero there, but I suspect even those were created from DOS saving itself in development. I've attached the latest good version. Since this now assembles to the correct binary, the only bugs are likely typos in comments or consistent typos in labels. Several letters look the same in the low-quality scan of the original sources, but I was usually able to figure out from the context what the correct letters were, so I hope the mistakes are minimal. From the formatting, it looks like they were using tabs, so my file uses tabs consistently. Bytes mattered back then, so that would make sense. dos1dup_source.asm 4 1 Quote Link to comment Share on other sites More sharing options...
+kheller2 Posted July 28 Share Posted July 28 Keep up the good work! I'm following along. This is very interesting to me to take such old source code and rebuild proper binaries. I know there are a few different assemblers out there, I used CC65 to assemble the sources for the OS, and that or another to do 1050 ROM and DOS3 DUP. I would be nice to have an Atari mainframe compatible assembler instead of hacking with sed/awk. 3 Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 28 Share Posted July 28 Fairly sure a lot of Atari dev work was done on PDP-11. There's a bit of an emulation scene for them so possibly the environment could be replicated. My experience on those - last 2 years of school we remoted in... which was probably being done by something like a 9.6k modem, maybe less. 1 Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 28 Author Share Posted July 28 2 hours ago, Rybags said: Fairly sure a lot of Atari dev work was done on PDP-11. Yup. That's been widely reported. But with the OS, BASIC, and DOS being contracted out, it's hard to be sure what environment they all used. The sources look like they would assemble with the Atari Assembler Editor cartridge with two changes: Eliminate the macros, and add line numbers. But another problem is that they created variables with "VAR *=*+2" to create a 2-byte variable, VAR, so the assembler just skips two bytes of output. At this point, I should create a GitHub repository with the PDF, my true-to-the-original assembly file, and my hacked-to-assemble version of the file. I've been thinking that what I would like to see is a 6502 assembler that is extremely forgiving on syntax with the goal of supporting any source that other assemblers support. I don't think I'm the one to do that, through. Quote Link to comment Share on other sites More sharing options...
ggn Posted July 28 Share Posted July 28 13 minutes ago, pcrow said: I've been thinking that what I would like to see is a 6502 assembler that is extremely forgiving on syntax with the goal of supporting any source that other assemblers support. I don't think I'm the one to do that, through. Not promising anything here, but could you be kind enough to mention some of the pain points on syntax? (context: I do maintain an assembler that has 6502 mode: https://rmac.is-slick.com) Quote Link to comment Share on other sites More sharing options...
Rybags Posted July 28 Share Posted July 28 (edited) There's source available for Atari Basic, the original OS and Dos 2.0s - so the original assembler used might be deducable. There's also plenty of documentation surrounding development (though also plenty of gaps) which could also help. Edited July 28 by Rybags Quote Link to comment Share on other sites More sharing options...
pcrow Posted July 28 Author Share Posted July 28 14 minutes ago, ggn said: Not promising anything here, but could you be kind enough to mention some of the pain points on syntax? (context: I do maintain an assembler that has 6502 mode: https://rmac.is-slick.com) The number one thing is implicit comments. A quirk was the use of "PER" as a label, which triggered a bug in 'xa' where 65816 opcodes are reserved words even when not in that mode. I reported that, and they may fix it. Some assemblers expect colons after labels, but that didn't impact me. The code expects to do character constants as #'0 or even expressions like #'A-'0+10 in hex conversion. The assembler I was using expected #"A" instead. Macro syntax is obviously going to be different on different assemblers. Fortunately this only used one, though I would have used a ton more for a bunch of things it was doing all the time. The syntax for .IF/.END and .TITLE wasn't supported by the assembler I was using. For reference, here's the line I was using to assemble the source: xa -E -XMASM -P dos1dup.lst -o dos1dup.bin <(cat dos1dup_source.asm | sed -e 's/;.*//' -e 's/\t...*\t.*\t/&;/' -e 's/\t=*\t[^.].*\t/&;/' -e 's/\t[*]=.*\t/&;/' -e 's/HILO/;&/' -e 's/[.]IF/;&/' -e 's/[.]END/;&/' -e 's/[.]TITLE/;&/' -e 's/^&/;&/' -e '104,107s/^/;/' -e "s/#'\(.\)/#"'"\1"/' -e "s/'0/"'"0"/' -e 's/[.]BYTE/.byt/' -e 's/ASL\tA/ASL/' -e s/^PER/PEER/g -e 's/\tPER/\tPEER/g' -e '100,$s/[*]=[*]+1/.BYTE 0/' -e '100,$s/[*]=[*]+2/.WORD 0/' -e '100,$s/[*]=[*]+5/.BYTE 0,0,0,0,0 /' -e '100,$s/[*]=[*]+40/.WORD 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 /' -e '100,$s/[*]=[*]+80/.WORD 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 /' -e '100,$s/[*]=[*]+[$]100/.WORD 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 /') 2 Quote Link to comment Share on other sites More sharing options...
pcrow Posted August 2 Author Share Posted August 2 I've published DOS 1 source files on Git Hub: https://github.com/pcrow/Atari_DOS1 The DUP assembly is from above, and I've already discussed it. The DOS assembly is from my disassembler with most of the important labels set based on the DOS 2 sources. 2 1 Quote Link to comment Share on other sites More sharing options...
sup8pdct Posted August 2 Share Posted August 2 If it helps any, here is a list of equates i figured out for dos1 based on dos 2 listing. 11E5 DFDPFN 11E3 DFDSSN 11E1 DFDCNT 11E0 FILDIR 116E FCBCNT 116C FCBSSN 116A FCBLSN 1168 FCBCSN 1167 FCBBUF 1166 FCBDLN 1165 FCBMLN 1164 FCBFLG 1161 FCBOTC 1160 FCBFNO 113F FNAME 113E FNAME-1 1137 SECTBL 112E DBUFAL 112D TEMP4 112C TEMP3 112B TEMP2 112A TEMP1 1129 SVDBYTE 1128 SFNUM 1127 CDIRS 1126 CDIRD 1125 DHFNUM 1124 DHOLED 1123 DHOLES 1122 CURFCB 1121 ENTSTK 111D ERREOF 1119 GREAT 1116 FGREAT 1111 ERRIO 10FF RETURN 10FB ERRDNO 10F9 ERRNSB 10F7 ERRNSA 10F5 ERRSYS 10F3 ERFNMM 10F1 ERRFN 10EF ERRPDL 10ED ERFLOCK 10EB ERDVDC 10E9 ERDFULL 10E7 ERFNF 10E5 ERRPOT 10D9 DFN 10D8 TDFR 10CD TDF1 10CB TSTDOS 10CA WD4 10C4 WD3 10A4 WD2 10A2 WD1 109A WD0 1090 SETDSO 107B DD1 1079 DELDOS 106A WRTDOS 1069 FSBR 105B FRESBUF 1058 SSBA 104D GSB4 1042 GSB1 1010 DSIO 0FC1 DERR1 0F89 SETUP 0F86 GSERR 0F6D GS4 0F59 GS3 0F52 GS2 0F2D GS1 0F2B GETSECTOR 0F05 FS3 0EFD FS2 0EF1 FS1 0EED FRESECT 0EEA DEAD 0EE3 DSIOER 0EDD BSIOR 0EDC DSYSIO 0ECD VTIO 0EC6 WRVTOC 0EC3 RDVGO 0EBA RDVTOC 0EA1 DIRIO 0EA0 WRTDIR 0E9D RDDIR 0E9B RDDELE 0E91 RDFNMM 0E8E RDIOER 0E82 RDNS2 0E5A RDNS1 0E52 RDNXTS 0E45 MVLSN 0E3C RWCSIO 0E3B WRCSIO 0E19 WRTN6 0DE6 WRTN5 0DC9 WRNERR 0DAF WRTN2 0DA6 WRTLS1 0D9E WRTN1 0D9B WRU1 0D8A WRTNXS 0D86 SDRTN 0D80 SFDSH1 0D69 SFDSH 0D60 SFD4 0D54 SFD3 0D47 SFD2 0D42 SFD1 0D2B CSFDIR 0D1B SFDIR 0D15 FDSC2 0D0F FDSC1 0D04 FDSCHAR 0D01 FNDERR 0CFD FDEND 0CF7 FD6 0CEB FD5 0CDF FD4 0CCF FD3 0CC4 FD2 0CBD FD1 0CB2 FD0 0CAE FNDCNX 0CA4 FD0A 0C98 FNDCODE 0C87 STDIGIT 0C70 CVD1 0C6B CVDIGIT 0C61 CVDY 0C51 CVDX 0C35 LD2 0C2F LD1 0C1B FDENT 0C18 LDDONE 0BFB LDCNT 0BF5 LDENT1 0BEB LDENT 0BE8 GDCRTN 0BCB GDCHAR 0BBF LISTDIR 0BB1 XF4 0BA6 XF3 0B88 XF2 0B67 XF1 0B55 XFORMAT 0B40 NOTE 0B3D PERR1 0B37 XP3 0B2A XP2 0B18 XP1 0B03 POINT 0B00 TLF 0AF5 TSTLOCK 0ADC XLC1 0AD1 XLCOM 0ACC UNLOCK 0AC5 LOCK 0AC2 XDELY 0AAF XDEL4 0AA9 XDEL2A 0AA4 XDEL2 0A76 DELETE 0A5F XRN3 0A55 XRN2 0A50 XRN1B 0A36 XRN1A 0A2B XRN1 0A1D RENAME 0A1A XFV 0A17 DVDCER 0A0A DVDCVT+1 0A09 DVDCVT 09EB SPECIAL 09C3 RRDIR 09BD CLUPDT 09B5 FNSHF2 09B3 FNSHF1 09B1 FNSHFT 09A9 CLDONE 098F CLOSE 098C SFNF 097B STATUS 0978 GET3 0959 GET2 0949 GET1 093C GETBYTE 0929 PUT1 090E PUTBYTE 08EF SETFCB 08EC DHFOX3 0888 DHFOX2 0885 OPNER2 0882 OPNER1 0860 OPN2A 0857 OPN2 0839 OPN1A 0813 OPN1 07FD OPEN 07DD ADI2 07CC ADI1 0788 FMINIT 0780 DFLADR 077C DFMSDH 076F DSIO2 0763 BSIO 074F INCBA 0712 XBCONT 0710 DFLINK 070E DFSFLG 070C SASA 070B SAFBFW 070A DRVBYT 0709 SABYTE 0700 FMSORG 3 Quote Link to comment Share on other sites More sharing options...
pcrow Posted August 3 Author Share Posted August 3 21 hours ago, sup8pdct said: If it helps any, here is a list of equates i figured out for dos1 based on dos 2 listing. That helps a lot! I had done the same thing, but there was one where you had a different address for the label, and looking again, you were correct. And there were a bunch I hadn't gotten. I've updated my files on GitHub to use the new labels. 2 Quote Link to comment Share on other sites More sharing options...
pcrow Posted August 3 Author Share Posted August 3 So one bug found and fixed: The end of DOS is set to $2680. That's in SASA at $070C, which is part of the DOS file. The DUP sources are separate, so it can't just reference an automatically generated symbol. Since it was manual, they didn't adjust it for the final build. The correct value is $262E. If you do a POKE 1804,46, then write new a new DOS file, it will be 1 sector shorter and BASIC will have 82 more bytes free. I did a quick test to verify this. I also verified that the DOS.SYS file still contains the same last RTS instruction that it is supposed to end with, so I didn't cut anything off. I'm more annoyed by the wasted sector from this bug than the wasted memory, but 45 years later it's fixed. 3 1 Quote Link to comment Share on other sites More sharing options...
pcrow Posted August 5 Author Share Posted August 5 I've updated things on the GitHub page for this. I now have the as-close-to-original-as-possible sources, cleaned up sources with more modern syntax that I can actually assemble, a combined single source file, and a modified source file. For now, the modified file takes all the buffers for both DOS and DUP and moves them to the end. This means it doesn't have to save them as part of DOS.SYS, so it's now 56 sectors instead of 64 sectors. I also eliminated a little bit of padding so the overall free memory is up slightly. 2 Quote Link to comment Share on other sites More sharing options...
pcrow Posted August 5 Author Share Posted August 5 And I've found and fixed the DOS 1 bug that annoyed me in the first place and inspired this project: If you create a file with 256 or more sectors, the directory listing only shows the low-byte of the sector count. It took a while to find because I was looking in the wrong place. All the code that manages the file sector counts was right (except for an initialization bug that I also fixed, but appeared to be harmless). I finally looked at the directory sector in a debugger and saw that the count was right there, too. The bug was in reading the directory. They left off a ",X" on the instruction to read the high byte of the sector count, which seems to have caused it to always get a zero (fortunately). That's fixed, and now directory listings are correct. Of course, the DOS 2 listings have these bugs fixed, but now DOS 1 has it, too. 3 1 Quote Link to comment Share on other sites More sharing options...
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