I'm not sure if Bochs and/or FreeDOS support LBA, but that doesn't really matter to us. (Note: Newer PC BIOSes use a different geometry scheme know as LBA that allows for much larger drives, but for a long time PCs could get by using CHS addressing because no one could dream of drives ever exceeding the 8.4 GB size limit. The largest allowable hard disk size is therefore 1024255 63512 or about 8.4 GB. The maximum allow value for H is 255 and that for S is 63. We can figure out the total disk capacity (in bytes) from: C HS 512. Each CD-ROM has a certain number of tracks (or cylinders) and each track has a certain number of disk sectors. The number of CD-ROM disks would correspond to the number of heads in a hard disk drive. Visualize a stack of CD-ROM disks all turning on a common spindle. Hard disks have a particular logical geometry that is specified in terms of cylinders/head/sectors or CHS. For the 10 megabyte example given, the corresponding bochs lines are:Īta0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14Īta0-master: type=disk, path="harddisk.img", cylinders=20, heads=16, spt=63, translation=auto, biosdetect=auto, model="Generic 1234" The following instructions describe how to make a disk image of arbitrary size. It was obtained by using dd_ to read the raw contents of a 1.44 megabyte floppy disk.Īnthony Richards was nice enough to post the following instructions to the RTEMS Users mailing list on how to create a file that is a hard disk image for use from Bochs. I used an old Grub floppy image from the 4.5.0 release series. TBD: Using Bochs Network Driver with RTEMS This page captures the instructions and setup information for Bochs and RTEMS. Formatting the Hard Disk Image using Linuxīochs is a free software simulator for PC compatibles available from .Formatting the Hard Disk Image using FreeDOS.I have Bochs version 2.6.7 fresh off Sourceforge, compiled with Is there some specification about what format VisualGDB expects? Is this scenario supported? I don’t know which end (VisualGDB or Bochs) interprets/sends the registers incorrectly but clearly they can’t talk to each other. I have looked through this forum but I haven’t found anyone either trying to use VisualGDB with Bochs. The 0x7ff4 and 0x7fe8 are addresses pointing inside the stack… You get the idea. You can’t have segment registers with values like 0x7ff4 or 0x0, on the other hand the 0xA0 in eax is likely to be the value of cs. Now I can see from the log file of Bochs that it correctly inserted the breakpoint at 0x21160 (which is an address in the OS image I know will be executed at initialization and I can confirm this by using the built-in debugger of Bochs), but the registers seem to be completely mixed up. When I select Debug with GDB from the Debug menu, Bochs launches just fine, accepts the connection from GDB and stops at the breakpoint. GDBServer/stub: x:xxxxxxxxxxxBochs-2.6.7bochs_msvc_gdb.exe -qĪnd specifying an additional command for GDB after it connects to the target: I managed to get it to connect by specifying a custom GDB stub in the Project properties: Since Bochs has a gdb stub, I am trying to pair it with VisualGDB since I am using Visual Studio as the development environment. Part of the development is running the OS in emulators/simulators, e.g.
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