Peter's z80.eu site blog
How to figure out structure / disk parameter of an unknown CP/M floppy disk ? 
Tuesday, May 20, 2014, 06:30 PM
Posted by Administrator

Meanwhile - more than only one time - I got mails with questions about unknown CP/M floppy formats. Often computer are mentioned, which are used in industry only, or names from SBC / self made systems were telled.

So how to figure out structure or disk parameter of a floppy disk of an unknown system ?

If you have access to that unknown system, take a look at the build-in floppy drive - at least you will get the model/type of the drive itself, and then you know how many tracks are used, e.g. if a TEAC FD55FV is used, usually 80 tracks is the number of tracks.
Also, you know then it's a double density drive, and MFM coding was used.

If you don't have access to the original system, just the floppy media, it's much more difficult. You can use devices like Kryoflux or SuperCard Pro, this is the most easy way.
If you own a PC with installed MS-DOS (not Windows!) and at least a floppy drive with the same physical media dimensions (e.g. 5.25 inch), you can use ANADISK.
ANADISK can help to get the needed disk definitions (e.g. Skew, DPB values etc.) for 22DISK, which can be referred as a companion software of ANADISK. To alter the definition file of 22DISK, you have to decompile them first (with STRIPIDX).

Entries look like this one:

BEGIN A1 Generic CP/M - SSSD 8"
DENSITY FM ,HIGH CYLINDERS 77 SIDES 1 SECTORS 26,128
SIDE1 0 1,7,13,19,25,5,11,17,23,3,9,15,21,2,8,14,20,26,6,12,18,24,4,10,16,22
BSH 3 BLM 7 EXM 0 DSM 242 DRM 63 AL0 0C0H AL1 0 OFS 2
END

(Note: 77 tracks were only used by 8" floppy disk drives)

A complete description of these parameter can be found in 22DISK documentation (usually included in the programs ZIP file).

You can take a look into a very helpful newsgroup message also:
https://groups.google.com/d/msg/comp.os.cpm/GxQ2ad3aHdI/nt8em8edXYQJ

You have to have an understanding about the disk structure of CP/M disks in general.
Take a look inside the CP/M Alteration Guide, Chapter 6.11 (see related link also).

After figuring out the parameters (these parameters typically are very often more or less similar or equal to already existing entries !), you can re-compile the disk definition file back to a binary file (with GENINDEX).
If all parameter were correct, you can use CTOD or DTOC for transfering single files, or you can use the main program to copy a whole floppy disk.


Alternatively you can try IMDA, which is part of Dave Dunfield's ImageDisk program package, which can be found at http://www.classiccmp.org/dunfield/img/index.htm

For more infos about transfer CP/M files, take a look also at my "Transfer page".
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A new ISA 8-Bit SCSI Controller... a Trantor T130B - but new problems too 
Tuesday, May 6, 2014, 08:20 PM
Posted by Administrator
Looking still around for a better SCSI Controller which fits in my original IBM PC/XT, I found a Trantor T130B, which should be more suitable for a generic usage, because it comes with an external SCSI connector, and more important, there is an ASPI driver for DOS existing.

Unfortunately there were two versions sold, some with, and some without a BIOS ROM.
I got one without a BIOS ROM, but I own an EPROM burner, so no problem yet.
But I then I discovered there is another empty socket U6 on the card, a 20 pin DIL one.
I figured out that there is also a PAL on the "boot-capable" version, but my version didn't have one. Fortunately some other smart PC owners already figured it out, what content the PAL chip has to have. See http://www.vintage-computer.com/vcforum ... AL-Part-13 for a thirdteen pages entry which describes what was done for figuring it out.
So I am confident it will be a booting harddisk soon, I only have to get the "burned" PAL.
Because PALs aren't reprogrammable, i choosed to take a GAL 16V8 instead of a PAL16L8.

Stay tuned for an update ... hopefully all things will go well.

Related link for a short description of that card.

Added later: I got a boot ROM message from the controller, but the controller itself does not recognize at boot time any hard drive. Seems I didn't programmed the GAL correct, or, also possible, the PAL file from the vintage-computer.com forum does not fit.
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Sega Dreamcast + VGA output ... possible for ALL games, but with a trick 
Saturday, April 19, 2014, 03:15 PM
Posted by Administrator
Recently I bought a Sega Dreamcast console, playing with it is *VERY* nice.

Especially Daytona USA 2001 is my favorite racing game, which remember me of the good old times ;-)
But the video output with the antenna / RF cable is NOT satisfying. So I also bought a DC VGA converter, which produces a very crisp picture on a VGA screen (you would love it, too).
Unfortunately some games (e.g. Soul Calibur) do not like to be shown on a VGA screen:

This is an artificial limit, because the games do run technically, regardless what video output is choosen. So I played a bit with that switch on the VGA converter box, and guess what I've figured out...

As you can see, even Soul Calibur runs with VGA.

How ? Power off the Dreamcast console and switch off the loud speakers.
The VGA converter box switch should be at position "TV".

Now power on the Dreamcast, and LISTEN the noise of the CD drive.
You will notice nothing on screen, screen is (still) black.
First 1-2 seconds, drive is starting to spin, making a noise without the stepper head of the CD drive itself. After another 2-3 seconds, the drive making it's first stepper noise, loading something from the GD-/CD-ROM itself.

After this first game loading noise is gone, switch the VGA converter box back to "PC".
You will notice a screen/the game is shown on your VGA screen again :-)

So switch it to TV, wait until the video output check is made (a few seconds), then just switch it back to PC. Mission completed.
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ZIP100 and IBM PC/XT ... works fine ! 
Thursday, April 10, 2014, 08:50 PM
Posted by Administrator
During my search for an easy transfer possibility from my modern i7 PC to my old IBM PC/XT, I was realizing that I forgot one thing... my old parallel port Iomega ZIP100 drive.

But I was early disappointed from Iomega's driver support. The GUEST software for DOS needs at least an AT machine (286 and above). Don't know why, may be because of the memory usage of Iomega's software.
But there was hope. Klaus Peichl, a german software author, wrote PALMZIP.SYS, which runs even with the oldest IBM PC. Unfortunately I already read something about compatibility issues also, so I was a bit sceptical. This was not necessary, because even my newer ZIP100 drive (DDXZ100P2) runs smooth with that PALMZIP.SYS version 1.22.


Boot with that driver works like a charm:


And that's the reward for all effort:

It makes sense to use at least MS-DOS 4.0 or above to get the drive space in one piece.

I am using a ZIP 250 USB drive for my modern PC, drivers are included in Windows 7 (no need to look for dedicated drivers).

See related link for the source of PALMZIP.SYS ... it's truely worth it's price.

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An odyssey with an 8bit Seagate SCSI controller ... 
Tuesday, March 25, 2014, 09:40 PM
Posted by Administrator
Not funny, but instructive.
I've tried to add a bigger SCSI drive to my PC/XT system, which uses a Seagate ST-02 controller. At the moment, it runs well with a small Conner 3040 HDD (= 40MB), but I liked to have a bit more HDD capacity.
So I obtained a Seagate ST51080N, which has in fact 1080MB capacity, but still a 50 pin interface. Unfortunately I was able to read some messages about Seagate ST-02, which describes a limit for bigger HDDs - but not clearly described what limit, but it seems to be related with the older ROM version of the controller.

So I decided to upgrade the BIOS from 3.0 to 3.32, found at http://ftp.mpoli.fi/hardware/ROM/SEAGATE/ ... but someone made a mistake describing that ROM.
It was NOT Seagate SCSI BIOS V3.32, but SyDOS SCSI BIOS V3.35 (but still based on Seagate's SCSI ST-01/ST-02 BIOS). It had some additions for Sygate's EZ135, which sounds nice, but was not helpful for getting bigger drives working properly.

I ended with using the Conner 3040 again, which works with the old BIOS version as well as with the new BIOS version.

Conclusion: Don't trust on file descriptions, nor on user messages about compatibility of old hardware. Seagate's ST-01/ST-02 is only able to operate with drives less than 1024MB. Nothing else.
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