View Full Version : Fergusin BigBoard II system diskettes?

January 18th, 2017, 02:58 AM

I have one in the basement. Bought the board in the early 80's and used it with two Tandon TM100 SSSD drives. Unfortunately has the system disks been lost. Anyone that can help? System has the original ROM.

January 18th, 2017, 07:23 PM

I sent Al Kossow IMD images of the 8" disks that came with mine when I purchased it used many years ago.

Unfortunately, the boot disks that I have are double density (ddboot.s1/ddboot.s2)

There is a single-density disk, however it is marked "do NOT try to boot from this diskette" (sdnoboot.s1/sdnoboot.s2)

There is an image of a disk bb5-8di, which has some information regarding running 5.25" and 8" drives together.


There are also several Big Board user disks there, as well as under the higher level Ferguson/User_Group directory.

If you need the manual, it is also on bitsavers:


You may need to build a boot disk, however I think that there are sufficient files to do so from the files on bitsavers.

January 19th, 2017, 04:15 AM
Thanks, Yes, I have all the manuals, hand-drawn schematics and all that. I will try to attach a 3.5" floppy as that would make life so much easier.

What software should I use to write a file like "DDBOOT.S1" to a floppy.

PS. Excuse me for the blatant typo in the subject line. It is "Ferguson" naturally :)

January 19th, 2017, 04:22 AM
Disregard my previous question. Opened up the ddboot.s1 file and lo and behold:
IMD 1.18: 30/01/2015 20:09:53
double density
"Big Board II" cp/m 2.2 #cp2-677-0093

Som IMD it is :)

January 19th, 2017, 09:56 AM
OK. So, I have gottem this far:
I have a Samsung SFD-321B floppy. Took the standard PC floppy cable, straight bit and cut wires 10 and 12. Wire 10 going from the BB connects to wire 12 on the floppy (as it is permanently wired as unit 1). Floppy works.

Using ImageDisk 1.18, I can now format a Non-HD 3.5" floppy and read sectors on it. I can use it to write down a KayPro image (kayIIger) and read it using the monitor command R0,1,1 for example. But when I try writing any of the BBII images, ImageDisk barfs and errors out.

The KayPro image seems to be 250k 10 sectors of 512 bytes. DDBoot.s1 for example appears to be 500k 26 sectors of 128 bytes.

What am I doing wrong?

January 19th, 2017, 11:28 AM
OK. We have some progress. The xerox-820 diskettes seem to work. Ie this one:

Boots up CP/M just fine. So why can I not write the BBII images??35547

January 21st, 2017, 08:29 AM
OK. We have some progress. The xerox-820 diskettes seem to work. Ie this one:

Boots up CP/M just fine. So why can I not write the BBII images??35547

Someone suggested that they might be 8" ones. Anyway, format and bytes/sector seems to matter. This works:

January 21st, 2017, 11:41 AM
Hi, you may already know this, but the 3-1/2" Samsung drive you have can be modified into an 8" drive very easily by changing three solder pads on the drive circuit board. The RDY->DS is clearly marked, DS1->DS0 is marked and the change speed option is marked as OPA1 or just OP. If the OP solder connection is bridged the drive operates at 360 rpm instead of 300 rpm. Image Disk can then make perfect 8" copies onto 3-1/2" disks. I did not modify the cable connecting the drive at all but used "NF6X" FD50TO34 adapter board purchased from OSH Park.
> Charles

January 21st, 2017, 02:49 PM
OK. We have some progress. The xerox-820 diskettes seem to work. Ie this one:

Boots up CP/M just fine. So why can I not write the BBII images??


The disk that you listed above is of a slightly different format than the DDBOOT.S1 (side 1) image.

Looking at the information with IMDV, it appears that the Xerox disk is 300khz, FM, 18 sectors of 128 bytes.

The DDBOOT.S1 image is 500khz FM, 26 sectors of 128 bytes. This is actually very close to a 3.5" HD (high density) disk. If you are using a double density 3.5" disk, then try a high density one.

You might want to look at the images in the Don Maslin archive:


Examining my monitor listing, it seems that the default on my board is to load a single density sector. The first sector then reads 12 additional single density sectors, performs some hardware setup, and finally the last thing that it does before it jumps to the CBIOS is to set drive zero's density control byte to double density.

January 22nd, 2017, 12:27 AM
Thanks all!
So, since I aleady have a cable that takes care of addressing, I should be able to bridge OP. I assume that I have to do this on both the drive in the PC, that does the writing and the one in the BB that does the reading?

Yes, I can format DDBOOT onto a HD diskette, but the BBII will not read it :(35639

So, I guess I could just use one of the images that work and copy files to it, but how. I tries 22DISK, but it did not work. Coould not read the floppy even on the same machine that I ran IMD on. Are there any utils I could use to copy files to either a CP/M floppy or to an IMD file?

January 22nd, 2017, 01:07 AM
I tried jumping OPA1, wrote the disk, put unit in BBII will not read disk. This is what the manual says:

5.3.1 Density Select
This siganl is used to distinguish between 1.6MB and 2MB Mode.
The interface pin No.2 can be used as Density Select Input signal by
attaching 0 Ω resistor onto "OPA" short plug when the High density media
is inserted. The "HIGH" level designates 2MB Mode and the "LOW" level
designates 1.6MB Mode. FDD can tell whether the inserted media is high
or Low density by checking the signal coming from mechanical switch which
detects the density selecting hole on the media.
5.3.2 Drive Select 0 and 1
Two trace plugs on the PCB, DS0 and DS1 are provided to select which
Drive Select line will activate the interface signals for a unique drive in the
daisy chain connection up to two drive units. Drive Select, when activated
logical "LOW", enables all the I/O lines except Motor On line.
This signal also controls the lightening of In-Use LED.
Type Contents
2 Mode
(2.0 / 1.0MB)
(Non-connection of "OPA")
Automatic Switching
2.0MB : If High density media is inserted.
1.0MB : If Low density media is inserted.
3 Mode
(2.0 / 1.6 / 1.0MB)
(Connection of "OPA")
Automatic Switching with "Density Select"
2.0MB : If High density media is inserted
with "Density Select" is "HIGH".
1.6MB : If High density media is inserted
with "Density Select" is "LOW".
1.0MB : If Low density media is inserted
"Density Select" is not available.

January 22nd, 2017, 12:16 PM
Hello Anders, as to your question yes, you have to modify the drive in the PC as well as the Drive on the BB. But first let me step back a minute and make sure we are on the same page. The modification to the Samsung will make it emulate a real 8" drive so it should be connected to the 8" connector on the BB FDC not the 5-3/4" one ( I don't know which you are using). This is the purpose of the 50 pin to 34 pin adapter mentioned. A caution on modification to the PC drive is that it will no longer work for the PC once modified unless you install a switch. Also, it is important to use the correct floppy card in the PC to generate the disks in the first place using Image Disk. I use the Apaptec AHA-1520A (or anything that uses the National DP8473N controller chip). I have purchased three Samsung and two Teac drives off Ebay and modded them into 8" emulation drives that work in place of my old 8" Shugart Drives.
Once modified, I use HD 3-1/2" Disks and they seem to work fine. I have also used SD Disks and they work most of the time. The Density Select line is no longer a factor after the modification as it is grounded out by the adapter card.
I have two drive boxes, one for the PC and one for the S-100 system. Hope this helps. I also have a PDF writeup but it's too large to upload here.
> Charles

January 22nd, 2017, 09:00 PM
Ah.. I see! I have a bunch of these drives, so I will see if I can make a cable to connect to the 8" connector. But what you are saying is that a drive so modified will let me write 8" images, on a PC, with the right controller and then read them as 8" in the BBII? The computer I use for this has an onboard chipset, but IIRC does it have ISA slots, so I could try a separate floppy controller.-

January 22nd, 2017, 09:56 PM
Hello Anders, yes, that should work and allow you to transfer and make copies of 8" image disk files on 3-1/2" disks and read them on the BBII. If you don't want to make cables, the user "NF6F" on this forum has made a 50pin to 34pin converter board that work well. Your existing PC floppy controller may work, but it adds uncertainty to the process. Dave Dunfield has a section in his writeup on the controller cards that work well. I chose to go the route of 8" disk drive emulation as there seem to be more software out there on 8" disks. Make sure you ground the DEN_SEL line in your setup, and you may have to play with the MTR_ON signal lines to get the drives to run. Research NF6P's GitHub site to see a good schematic as to how everything is connected.
> Charles

January 23rd, 2017, 12:54 AM
Do you have a link? I cannot seem to find NF6F or NF6P here or on GitHub... edit: found it https://github.com/NF6X/fd50to34

January 24th, 2017, 07:51 AM
OK. Posting here again as this is a disk issue :) Was able to add files to a RAW image, convert to IMD and put on floppy. Copied BB2FORMT.COM. It runs, but complains about the rotational speed, says it is 199ms, which equals just over 300rpm. That makes me think that it thinks it is an 8" diskette? Is there a separate format program for 5.25" on the BBII?

January 25th, 2017, 09:47 AM
Just adding: To run at 360rpm you need to:
1. Jumper OPA1
2. Cut and gound density select
3. Use a HD diskette

January 25th, 2017, 02:00 PM
Anders, I don't know anything about the Big Board Computer but software that checks for rotational speed is very possible. In the original article from Marcus Bennett he mentions the problems he had with his Cromemco system in detecting rotational speed of his disk drives which prompted him to do the Samsung 3.5" modification. If you have access to the source code, you could look for code snippets on "Speed" to see if that may be the issue. Marcus Bennett's article is at...
> Charles

January 25th, 2017, 10:23 PM
I have been trying to find the source for BB4FRMT.COM, but have been unable to do so. This is not a major issue for me at this time though. There are other formatters on the BBII user's disks from Micro Cornucopia so I will check out those. They have source included.

I saw that someone did a really nice adapter card from 50 to 34 pin, gerbers and all, but do you know if anyone has hards for sale? I can order from the place I normally order PCBs, but overhead for a single card will be high.

January 25th, 2017, 11:08 PM
Anders, if you mean the FD50TO34 they can be purchased from OSH Park $24.00/3 for boards only, or you can get the fully assembled FDADAP board from D-Bit $40.00.

January 26th, 2017, 03:15 AM
Yes. Thanks for the links!

January 29th, 2017, 05:01 AM
Just ran across this and am interested in the BBII use of multisize disks. I have a BBII I put together in the early 80 with 8" disks. It's still on the shelf with all the disks. Haven't run it in years but it holds fond memories and I hesitate to part with it. Back in the day there was a kit from, IIRC, Andy Bakkers (may have the spelling wrong), from the Netherlands to allow running 8" and 5" at the same time. He ran ads in MicroCornucopia and came to the SOGs. Not sure if that solves the currently discussed issues. I don't have it but I consisted of an updated PAL to allow software switching of the needed signals and some software. I see that the contents of the PALs are available on bitsavers so it might be possible to locate someone with the information or recreate it. Also have a Xebec board for hard drive interface but never got it going.

January 29th, 2017, 10:38 PM
Interesting! Yes, I remember Andy from his articles in Micro Cornucopia. I am still looking into this and have been trying to format disks on the BBII. Sadly BB2FORMT.COM appears to format 8" only. I have played some with the source of the BBI formatter with limited success. The formatter does two calls past the CBIOS jumptable rendering it incompatible. Further is the address of the controller different. I fixed that, but the biggest hurdle remains: On the BBI the controller was connected to the NMI line. On the BBII it is connected to CTCA. Thus when the formatter does a HALT, waiting for the controller to finish, it hangs. Still struggling with that. Found a DUTIL.ASM that says it is for BBII and claims it can format one track. That code uses DMA instead so I might go that route instead.

I use this nifty crossassembler on Linux: http://www.z80cpu.eu/projects/78-data-articles/projects/76-mdz80

February 4th, 2017, 09:07 PM
The BBII monitor expects the boot track to be SD, even on a DD disk. Thus a 5.25" boot disk will have a SD track 0 with 18 sectors and the rest of the tracks are 9 sectors DD with 512 bytes/sector. CBIOS does the deblocking.

The CBIOS can handle 256/512/1024, but I chose 512 as that seemed to be what my PC writing the disks could handle reliably. In fact at 250kb MFM it would produce disks that were readable on the BB, but not on the PC, 300kb were readable on the PC.

So I wrote a program that created a dummy IMD file with the above parameters, verified that the disk written had the sectors in the right place, as read by the BBII monitor.

Then wrote a SYSGEN/PUTSYS program that takes an empty infile, a cpm.com file and created an IMD image, with CBIOS and CPM on the correct sectors.

It now loads CBIOS and CP/M, but then exits to the monitor, so I have to dig a bit more.

February 5th, 2017, 11:41 AM
OK. Have a bootable diskette. Will create a master image with those (IMD-format) and upload when done.