NT4 and 16 GB FAT16 drives-possible?

[ovctvct]

Well, it's been mentioned that NT4 supports 256KB clusters in FAT16, allowing 16 GB partitions. But for some reason, it does not format anything above 4 GB and 64K clusters, tried formatting a 6 GB partition, but this came up, even if I manually specify cluster size:


even tough 256 KB clusters are supported, and yes, I have SP6a installed and set up with an IDE drive if that matters.

[Overdoze]

Well I've managed to create a 16GB partition in setup, by simply allocating all the space to a single partition. It automatically formatted with 256KB clusters and warned me that this can cause issues with OSes that don't support larger clusters.

[ovctvct]

How? I tried that too, but even if I use the sp6a atapi.sys it's limited to 4GB, no matter how large the HDD is. I used virtualbox if that matters with a 9 GB Vdi and IDE.

[Overdoze]

Ah, my bad, actually it warns you if you exceed the 2GB limit. I can't get 16GB formatted either. However, sector size is also a factor here, with 128/256KB clusters only being supported if sector size is above 512B (according to this Microsoft support page).

[ovctvct]

So virtualbox doesn't support >512B sectors? But does pcem support them by any chance?

[sparcdr]

PCem does not support >512B sectors. Regardless of the sector size, the hard limit is imposed due to the Int 13 limitation of the hardware itself. [1] [4]

SCSI's used in DEC/SGI/Sun boxes in the 90's had similar boot restrictions as well. In the 90's, boot media for those machines had to be 512 bytes (CD's) while PC CD-ROMs are and as far as I know have always been 2048 bytes. There were never 2048 (2K) hdds during the IDE/ATA era afaik, and PCem does not expose an option to change the size of anything but the # of sectors (Maximum 63), heads (Maximum 16), and Cylinders (Maximum 16383) for a maximum hdd size of 8063mb. At the time the only bigger drives were UltraSCSI 9.1GB drives used in UNIX'y systems. [4]

The bootloader on x86 machines has to lie within the first mb due old MBR implementations, and depending on how the bootloader was implemented, the kernel segment must also generally lie within the first mb of memory as well, with the exception of that time being SPARCStation 5's, where the kernel memory limit is 2.6mb and the disk limitation being 2048gb as it used a single-ended narrow scsi interface, though in practice the highest capacity produced for pre UltraSCSI-3 generation hardware was something like 18.2gb, where 9.1gb was the most common at the end, and 4.3gb scsi being the most affordable throughout that timespan.

BIOS Int 13 - the 8.5 GB limit

At most 1024 cylinders (numbered 0-1023), 256 heads (numbered 0-255), 63 sectors/track (numbered 1-63) for a maximum total capacity of 8455716864 bytes (8.5 GB). This is a serious limitation today. It means that DOS cannot use present day large disks.

[1]

8063mb * 1024kbytes * 1024bytes = 8454668288 bytes. 8455716864 bytes - 8454668288 = 1048576 bytes / 1024 kbytes = 1mb difference, hence the first 1mb bootloader rule I suspect. Please note the 1000 vs 1024 rounding retardisms of hdd marketing applies and explains the truncated storage / differences. [2]

[1] http://www.tldp.org/HOWTO/Large-Disk-HOWTO-4.html (Applies to any os on that era's hardware)
[2] http://www.scsifaq.org/scsifaq.html#Performance003
[3] http://www.scsifaq.org/scsifaq.html#_Hlk411842161
[4] https://en.wikipedia.org/wiki/Parallel_ ... imitations
[5] https://en.wikipedia.org/wiki/Parallel_ ... _and_ATA-1