- VCF South West - June 14 - 16, Davidson-Gundy Alumni Center at University of Texas at Dallas
- VCF West - Aug 2 - 3, Computer History Museum, Mountain View, CA
- VCF Midwest - Sept 7 - 8 2024, Schaumburg, IL
- VCF SoCal - Mid February 2025, Location TBD, Southern CA
- VCF East - April 2025, Infoage Museum, Wall NJ
-
Please review our updated Terms and Rules here
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Fergusin BigBoard II system diskettes?
- Thread starter AndersG
- Start date
BBII system diskettes
BBII system diskettes
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.
BBII system diskettes
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.
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
I use this nifty crossassembler on Linux: http://www.z80cpu.eu/projects/78-data-articles/projects/76-mdz80
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.
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.