Sounds like the CHS data you noted down might not be "true" CHS (if we can talk about "true" CHS at all on a flash device...), but rather LBA- assisted or "Large-shifted" geometry. Have you forced the disk mode in your ~2000 PC when doing the auto-detection? If not, it probably uses LBA by default. Most BIOSes I have seen allow to change the geometry mode and then display the corresponding CHS values immediately next to it. I'd expect your BIOS to have settings like "standard", "Large" and "LBA". The one you want for compatibility with your 486 is definitely "standard" (meaning 24-bit CHS).
Mateusz On Mon, 02 Jan 2017 02:33:10 +0100, userbeitrag wrote: > Hello again! > I just wanted to report back for all of you who helped me and gave great > inputs. > > Thanks for the CHS/LBA info. > This is an IDE Flash module that goes directly into the MBs slot. It > doesn't allow to connect another device beside it, so it also doesn't > have a master/slave jumper. > > It has a capacity of 512 MB. I tested it on another PC, from around > 2000, which auto-detected it as C/H/S 993/16/63 (no boot-up as it was > still empty at that time, I just did the BIOS auto-detection). > > > On the 486 I've put that in for the IDE device as custom type 82. The > other values, LZ and WP, I left at 0. I assume for a flash drive they > are simply not important. > > But it doesn't boot. It halts with the error message: "partition > signature != 55AA" > > I've personally checked: all partitions and the MBR have that signature. > > I managed to find an old external USB HDD which has an IDE interface > inside, and I connected the flash module to my regular PC. > > > # dmesg | tail [23705.522176] scsi 7:0:0:0: Direct-Access > > TRANSCEN > D 0000 PQ: 0 ANSI: 0 > > [23705.522746] sd 7:0:0:0: Attached scsi generic sg3 type 0 > > [23705.523265] sd 7:0:0:0: [sdc] 1000944 512-byte logical blocks: > (512 MB/489 MiB) > > [23705.524141] sd 7:0:0:0: [sdc] Write Protect is off [23705.524145] > > sd 7:0:0:0: [sdc] Mode Sense: 27 00 00 00 [23705.525012] sd 7:0:0:0: > > [sdc] No Caching mode page found [23705.525018] sd 7:0:0:0: [sdc] > > Assuming drive cache: write through [23705.528556] sdc: sdc1 sdc2 > > sdc3 [23705.531653] sd 7:0:0:0: [sdc] Attached SCSI disk > > > # parted /dev/sdc print Model: TRANSCEN D (scsi) > > Disk /dev/sdc: 512MB Sector size (logical/physical): 512B/512B > > Partition Table: msdos Disk Flags: > > > > Number Start End Size Type File system Flags > > 1 32,3kB 52,7MB 52,7MB primary 2 52,7MB 74,0MB 21,3MB > > primary 3 74,0MB 480MB 406MB primary fat16 boot > > As you can see, the third primary partition is for FreeDOS. I've decided > to create a 50 MB partition for DR DOS and a 20 MB partition for MS-DOS > or any other DOS I want to test (like PC DOS, PTS-DOS). > > The third partition has been made bootable with "format c: /s /q". I've > also rewritten the MBR using "fdisk /mbr". All partitions are formated. > The first two partitions are otherwise empty. > > I've also used Linux's dd (e.g. "dd if=/dev/sdc1 bs=512 count=1 > of=bootsec1.bin") to check if the boot signature 55AA is present on all > partitions + on the MBR and it is. > > > Thinking logically: If the BIOS wouldn't check, it should boot. The MBR > code should find the active partition #3 and chainload the bootsector. > This should include the bootcode for FreeDOS, since I've formated it > with /s and the system files are on the parition. > I hate it when a BIOS checks stuff that it rather shouldn't care about! > > Any other error message and it could have been FreeDOS, but I am sure > this one if from the BIOS _before_ it executes the MBR boot code. > > > > Maybe the next time I will try only one partition first... Anyway: > again, I've come to a halt for now. > > I appreciated your help. > Happy 2017. > Userbeitrag. > > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most engaging > tech sites, SlashDot.org! http://sdm.link/slashdot ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
