[offer] Microsoft Basic compiler v5.35/5.36 for DEC Rainbow 100 [RX-50] (SCP) [edited]

callmejack

This is version 5.35 of Microsoft Basic compiler for Dec Rainbow 100 (under MS-DOS). One of the disks is in RX-50 format and the second disk is a standard IBM compatible 180KB floppy disk which is readable by any IBM PC and compatible and which contains version 5.36.

https://mega.nz/file/mCBGFLSY#2J7yYk3GkIUMEK-DaIIZO0MkF-nhl6qm_t_ChTrESG8

esons

Cool, to find this here! I recently got a DEC Rainbow 100, but I dont have any disks. How do you create the disks, to use on a DEC Rainbow 100? You can transfer the image by serial somehow and write an image on the machine itself? Or you need an old floppy drive on an old PC? Thanks!

SomeGuy

Non-copy protected stuff can be written using ImageDisk on a PC with a 1.2mb floppy drive attached via a real floppy disk controller.

Otherwise, one needs a flux-level copying device such as a Kryoflux, SuperCard Pro, or Greaseweazle along with a 1.2mb floppy drive.

Note that KF RAW and SCP dumps need to be "reconstituted" to remove noise, otherwise it is like making a photocopy of a photocopy.

SomeGuy

Hmm. So one of the disks is a program disk and the other is an update. But note that the label on each says "1 of 2". I think there should be an additional disk with some more utilities.

callmejack

@SomeGuy You're correct, I should have written v5.35 / 5.36, I will update my post.

I had a hard time understanding this package. First there is the "1 of 2" on the label suggesting there are missing floppies and then the floppy "system for MS-DOS" on which the previous owner had written "RX-50 format" but in reality is a standard MS-Dos format instead of the RX-50 format.

Anyway, on the documentation there is an addendum at the beginning that describes the content of the 2nd missing floppy :


The missing file is Link.exe, which apparently is the same as the one provided on the MS-DOS 2.05 for DEC Rainbow.

I have built the missing 2nd floppy with the link.exe program, in RX-50 format and also a RX-50 format version of the 5.36 update. The content of the floppies are also included in seperate directories:

https://mega.nz/file/OSgBBIBY#CC-8xnYxABC5E74naB9L7dpNCafVreBh7uW85L_bA8k

SomeGuy

DEC Rainbows can, apparently, read IBM PC 160k/180k single sided disks. So it is not too surprising that Microsoft might distribute a Rainbow title using an IBM PC single sided format.

callmejack

Interesting, I didn’t know that.

elgibbons

@SomeGuy - could you explain what you mean by "reconstituted" KF dumps and possibly the method? Even though KF was not expressly intended to write back data to disk, I wonder if the process may be performed in such a way where a raw KF dump written back to disk may not be distinguished from the original.

SomeGuy

So what a kryoflux, SCP, or similar device does is just record the raw digital output of the floppy drive's "data out". The drive's "data out" outputs a digital signal that represents when the magnetic polarity under the drive head reverses. This change is called a "flux transition".

An ideal MFM encoded signal will consist of three specific frequencies. That is, the digital signal will rise or fall according to a clock.

That is how a signal written to a floppy disk from a real floppy controller would look.

You will NEVER get that back with that level of exactness from a real floppy disk. On a real floppy disk, the transition will happen a little earlier or later. If it is close enough, a real floppy controller reading it back, or software decoding a stream will still figure out what it means.

A kryoflux stream file records the signal exactly as the drive outputs it, including that small variance or "noise".

If you write a kryoflux stream file back, you write that noise and add new noise from the imperfect magnetic surface.

Now, if your original disk was in good shape and the signal on the disk was strong, you might be able to write it as-is to a new disk and it might just be readable. But if there was any damage or if the drive that wrote it was a bit off or something, even though it might decode ok, your new copy might have readability problems.

So when you are writing disks with a Kryoflux, or similar device, you want to first reduce the disk image to a "lowest common denominator". For a standard IBM PC image, that might be an unstructured ".IMG" sector image. For an oddball non-DOS FM/MFM disk, either ImageDisk or Teledisk is usually best. For copy protection, at least on IBM PC titles, usually a decoded MFM stream is needed (contains sector headers, footers, gap data, and so on).

You then take that image and programmatically create a Kryoflux stream file or .SCP file. The easiest program that I know of is the HxC software tool. Just drag and drop your IMG/IMD file and then export to a Kryoflux dump. The resulting dump will not contain any "noise". When you write that to a floppy, it will be comparable to what a real floppy controller would write, and will create the best possible signal on the floppy disk.

I refer to this nice clean programmatically created stream file as "reconstituted".


Ideal, programmatically generated MFM signal. Three exact frequencies.



What you will actually read back from a disk.

callmejack

@SomeGuy do you systematically reconstitute the kryoflux and SCP dumps before posting them on winworldpc and would you recommend that contributors do it?

SomeGuy

No, I include SCP and KF dumps "as-is". The reason for this is just in case I make a mistake analyzing the copy protection, or if there it a decoding error in IMG/IMD files, one can go back to the source file and re-analyze it.

Also, IMG/IMD files may omit stuff that is actually present but not part of a proper disk image, such as hidden disk mastering information or partially degassed data on unused tracks (such as the second side on these disks). Having the original SCP/KF image lets people analyze that.

I think there have been only a couple of exceptions to this, where I have had to undo user modifications to a copy protected disk image in order to provide a fully usable image. But in those cases I included both original source and reconstituted images.

Now, if one is trying to write a disk for use on a real computer, and the only tool they have is a Kryoflux or SCP, I advise using the IMD/IMG files if available, opening it in HxC and exporting to a clean KF/SCP stream. Copy protected disks may need much closer analysis. I know that is confusing, but these are not simple tools.