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RichCini
November 26th, 2008, 09:58 AM
All:

Iím working on adding support in the Altair32 Emulator for directly reading WAV file samples of audio cassettes. Initially, Iím working with the 88-ACR but it should be a snap to modify that code to support the KCS. The sample tape provided was for the MITS Disk Boot Loader. I knew that this was provided in PROM, but I didn't know it was on cassette, also. I have the source code and ROM image, but no manual of any sort.

Anyway, me and a buddy of mine are starting to parse the WAV samples and it would help greatly if we could get a copy of the manual for the tape version of the DBL. The owner of the tape doesnít have it. What Iím really looking for is the toggle loader or whatever was used to bring the DBL in from cassette.

If anyone has it and would be willing to scan it for me, Iíd appreciate it. Thanks!

Erik
November 26th, 2008, 07:10 PM
I'd love to see that as well. . . :)

RichCini
November 26th, 2008, 08:08 PM
I don't even really need the manual, but I need the code for the first-stage loader. The tape has data on it we can't readily identify yet. We think it might be the load address and possibly some other data, but without seeing the loader, we can't be sure.

Erik
November 30th, 2008, 09:14 PM
I have the binary image for the DBL paper tape. . . would that help?

RichCini
December 1st, 2008, 08:02 AM
I have the binary image for the DBL paper tape. . . would that help?

Erik --

Yes, that will certainly help clear up some things. I have the ROM binary which of course doesn't have any loader info. I spoke to someone yesterday who worked at MITS in 1975-1977 who mentioned that the DBL was loaded with the same kind of loader as with the other tape (either paper or audio) formats which is the same as in the development system manual. I was hoping that the DBL manual -- which seems to be as scarce as hen's teeth -- would confirm that only a small toggle loader was required and that the tape didn't contain a secondary loader as with BASIC.

So, with a combination of your tape image and my binary image, I should be able to determine if there is indeed a secondary loader.

Erik
December 1st, 2008, 08:43 AM
Erik --

I was hoping that the DBL manual -- which seems to be as scarce as hen's teeth -- would confirm that only a small toggle loader was required and that the tape didn't contain a secondary loader as with BASIC.

So, with a combination of your tape image and my binary image, I should be able to determine if there is indeed a secondary loader.

The zip file should be in your inbox now.

If you ever locate the manual please let me know. . . :)

billdeg
December 3rd, 2008, 07:32 PM
Exactly what manual are you looking for?
Bill

RichCini
December 4th, 2008, 05:06 AM
Bill --

Your question sparked me to look in unusual places for the manual for this code. I (and many others) assumed that the manual for the Disk Boot Loader existed as a separate manual, but it appears that it doesn't. There are two manuals relating to the Altair Disk system. The first is the 88-DCD manual, which is only for the hardware. I looked at the manual closely and indeed, there's nothing in it about software.

But there is a separate AltairDOS manual which, frankly, I never actually read because I don't use AltairDOS. This manual, which I have on my Altair32 site, contains the elusive toggle bootstrap code in Appendix F.

Thanks again, Bill, for asking the right question :-)

billdeg
December 4th, 2008, 06:33 AM
I believe I have the manual, but I don't have any disks. Glad you found what you were looking for. I have the manuals, a MITS drive, and associated controllers with cables.

Yes I would like the disks if anyone has the boot disk lying around. :-)

Bill

RichCini
December 4th, 2008, 11:40 AM
I believe I have the manual, but I don't have any disks. Glad you found what you were looking for. I have the manuals, a MITS drive, and associated controllers with cables.

Yes I would like the disks if anyone has the boot disk lying around. :-)

Bill

Bill --

Although I think I found the answer I needed in the AltairDOS manual, if there was indeed a separate manual I could compare the loaders. So, no rush, but if you find a separate manual, please let me know.

I have an image of an AltairDOS disk as part of the Altair32 but so far, no way to move it to a real disk, primarily because I don't have an Altair disk system. If you want to take a shot at developing a utility, you can use the image I have.

billdeg
December 5th, 2008, 07:33 AM
I probably have what you have the Altair DOS User's Manual from June 1977. The first few pages go through how to bootstrap the system under various situations, etc.

What I plan to do, once I get a boot disk, is to use a turnkey system monitor to load the DOS bootstrap.

Bill

deramp5113
March 30th, 2013, 01:49 PM
I apologize for the very, very delayed response to this old thread, but I just happened to be in the middle of trying to make the tape based DBL Rev 4 work, so here's some additional information:

The DBLrev4 tape contains a checksum loader (just like BASIC tapes), which in turn, loads the disk boot loader. The checksum loader is designed to load at 0x3f00 which is the same as for Extended BASIC, so enter the same front panel bootloader for the DBL tape as you would for loading Extended BASIC from tape. Sense switch settings are the common Version 4 loader settings for the terminal device and load device.

The DBL code is loaded by the checksum loader into memory at 0x5c00. The tape DBL code ignores the loader present in sectors 0-n on the disk and instead, loads all of BASIC itself starting at sector 8. This causes two problems that the ROM DBL does not have:

1) Disk BASIC versions 4.x will load, but Disk BASIC versions 5.x (and the 300-x versions) won't load because they end up overlaying the loader (they extend to 0x5e00).

2) The DBL tape loader won't boot CP/M and other disks which don't duplicate the disk layout of Altair BASIC and Altair DOS. For example, Altair CP/M boots just fine with the DBL ROM (because the ROM loads the disk's own loader from sectors 0-n), but the tape based DBL won't boot an Altair CP/M disk because it ignores the disk's own loader.

I have created a tape DBL that duplicates the behavior of the ROM DBL. The front panel loader is the same as for the DBLrev4 tape, the checksum loader is also the same, however, the DBL code that is loaded from tape reads and runs the disk's own loader code stored in sectors 0-n just like the ROM DBL does.

Mike