tep392

He can edit his first post now.

Someone wanted this very badly. Sold for $371.68!!!

I can confirm that Mark was still working on the BIOS at the time of Curt's death. I also learned during a phone conversation with Curt that Mark's return to the XM was a barter deal. Curt agreed to do some design work for Mark in exchange for him finishing the BIOS. I don't recall the details, but it seems in this one instance that Mark actually kept his word.

No worries. I missed the live event, but will try to check it out later.

Why do you perpetuate your made up "wafer drive" name for the "Atarimax Ultimate SD Multi-cart"? If I google the "wafer drive" it just leads me to your Ebay listing. Oh, I get it now.

Newell offered an optional switch for disabling Omnimon (daughter board version) because there was the possibility of software checking for it's presence and not running. I don't know how much of this actually went on back in the day, so it may or may not be an issue for the average 800 user today. I think a dipswitch to disable the ROM at C000 and any reset vector modification scheme would probably be good to include, just in case. If it's something that is needed more frequently, then maybe a switch located at the top edge of the card to make it possible to switch off without removing the card. I hot glued the switch to the top of my OS board for my daughter card Omnimon so I can easily access it by lifting the cover. I have no interest in drilling holes and mounting switches on my relatively pristine machine.

I assumed the Ramrod did it the same way. Ramrod is supposed to work with Atari ROM, so it must be able to change the reset vector is some manner. Or maybe it doesn't. The daughter board version sit's in the F000 slot, so it can decided if C000 or F000 chips are selected. It has an 8 input NAND gate plus some other gates that are part of the address decoding logic. The daughter board also allows a switch to be added to disable the reset vector trick or disable omnimon completely. I'll try putting the Atari ROMS in my ramrod and see it the Omnimon still works in the same manner. Edit: I put the Atari ROMS in and now option/reset and select/reset no longer work. So the Ramrod doesn't work the same as the daughter board. A patch to the reset vectors at $FFFA-FFFD is required. The OSN ROMS already have this. I then found these installation instructions which explain it. OMNIMON ! INSTALLATION INSTRUCTIONS NOTE : If you purchased OMNIMON! installed in the OS ignore this piggy-back board, sheet. Instead, refer to the installation instructions provided with the board. The OMNIMON! program comes in a 2732 compatible ROM. This can be ln sPecial hardware such as RAMROD MMOS by NEWELL INDUSTRIES which accepts a 2732 in the $C000 block of memory. Follow the instructions provided with this hardware for installation of the chip. To make sure the installation is correct up to this point, power up he computer. If everything appears to be normal, try entering OMNIMON 1 from BASIC with a • X=USR(49152 ) If it fails this test then double check tne installation of the chip. If this works properly then proceed with the next paragraph. For proper operation of OMNIMON! the following locations should be changed m the OS (assuming your OS is in EPROMS): $FFFA-$FFFD - $CE, $CF , $F5 , $CF This allows the SELECT and OPTION keys to work in conjunction with SYSTEM RESET for entering OMNIMON! • If If the OS chips were provided with the RAMROD then these changes have already been made. If you do not make this mod then it is possible to enter OMNIMON! from BASIC with 1 X=USR( 49152) However, this is less convenient than the SELECT/RESET or OPTION/RESET technigue, which interrupts any program which may be running. If the system fails to power up after you have made these mods then one mods were not done correctly. When done correctly the system should power up normally and you should be able to enter OMNIMON* with SELECT/RESET or OPTION/RESET. Installation of OMNIMON! is‘now complete.

It’s done with the address decoding on the ramrod. If you have replicated it, then it should work fine. Reads from FFF8-FFFF will enable the chip at C000 instead of the OS Chip at F000. It’s rather simple and clever.

You can find them in this topic.

They could have made ROMDOS auto initiate at startup, so they must have made the conscious decision not to. As a user, I would rather have the option of what DOS I boot up with, so I think that makes sense.

I figured it out. If I use Omnimon to read $FFFA, I get CE CF F5 CF F3 E6. So the daughter card is using address decoding to intercept the 6502 boot vectors, giving the Omnimon control when the machine is powered up or reset.

I've confirmed that it alters the VBREAK vector. This is why BRK instructions will jump into omnimon. I'm pretty sure the board has to be enabling the 4K rom when the OS is copying the vectors from ROM to $0200. I should be able to verify by comparing the vector table in the OS ROM to the Omnimon ROM.

I haven't looked into why it works, but somehow the Newell daughter card is able to intercept the interrupt when select/reset or option/reset is pressed. The daughter card plugs into the C014599B OS socket and re-uses the Atari ROM. There is no other ROM except the 4k Omnimon or Omniview chip. Edit: The only thing I can think is that the board intercepts the interrupt by switching in the Omnimon/view rom when the interrupt vector is read. Edit2: I just popped into omnimon from the Memopad and checked the vectors at 200-217. The VBREAK vector at 206,207 is $C0C4. It had to be set by some address decoding trickery during the OS boot process.

Edit: From the manual Turning on 80 columns: if you are not using one of the programs that activates 60 columns automatically, you can do so from the keyboard by holding down the START and SELECT switches and then very briefly pressing the OPTION switch. Then press the BREAK key to clear out the line buffer, it is important that you hold down the OPTION switch as briefly as possible (more of a tap actually). This is because these three switches are monitored during the vertical blank Interrupt (VBI). If the VBI detects the closure of all three switchs, it doe^ a JSR $C001 to initialize OtINlVIEW. Holding the switches down longer than one VBI causes the VBI to be reentered, pushing more stuff on the stack and eventually causing the stack to overflow. A great way to lock up your computer! Other ways to turn on 80 columns are •X=USR(49152)' from BASIC or 'JSR $C00r from assembly language.

RTM

Omniview is switched between 40/80 modes with certain keystroke combinations. No boot disk required. It's best to read the Omniview manual for details because hit has other features besides 80 columns. https://archive.org/details/Atari_OMNIVIEW_manual/mode/2up

This versions L and R Omnimon feature looks interesting.

It is a function of the DOS to retain the contents of the battery backed RAM before it attempts to initialize the Ramdisk. For example when SDX boots, it will check if the Axlon RAM is formated as a ramdisk and will retain it's contents if it is. If not, it will initialize the ramdisk if you have it setup to do so. I've seen other DOS ramdisk drivers do this also but don't recall off the top of my head which ones. Booting from a ramdisk is another matter. I think there would need to be some support in the OS for this. The R and L versions of Omnimon have ramdisk support and do actually have a function to boot from the ramdisk. I have not tried that out yet, but I hope to spend some more time soon investigating the capabilities of the L+U Omnimon I have in my Ramrod board.

I added battery backup to my 512K sram based Axlon compatible board so I wouldn't lose files if my machine locks while working on a program. I assemble code from the ramdrive since it is so much quicker. I pulled the board out while testing another Axlon board, and when I put the thing back in a few days later, the files were still there. The geek in me loved that.

I should add that the switch needs to be in the center position which disables the interrupts for SELECT and OPTION/RESET. Otherwise the computer locks when booting.

It works.

Maybe you could get it to run out of RAM if you manually called the DOS init routines instead of doing a cold start. Some custom boot code could be written to read the binary into ram and initialize it. Regarding the Omnimon board, I have one so could try out romdos on it. I don't see why it wouldn't work.

The lack of Ramdisk support is a big down side to this early version of MyDOS. My preferred DOS is SDX which when used on the 800 makes an extra 3K available in Atari BASIC compared to DOS2.0 with Axlon Ramdisk driver.

I didn’t try it without the ROM but figured that is what the DOS and DUP files were for. Do you know what Autorun does?

But who doesn't love the sound of a bad sector check on an 810 drive? First thing I did with AMAC was back it up and disable the bad sector check, so I wouldn't have to listen to it every time I switched between editor and assembler.