Re: Filesystem creation

Riley Williams
2002-05-12T23:07:50Z

Hi Lars.

>>> I'm trying to run the image "comb" on an IBM PS/2-30.

>> I don't know that particular model, but have a PS/2-70 here and
>> that has an ESDI hard drive.

> AFAIK, it's an updated XT. The difference is much interface
> electronics integrated on the motherboard. Video (MCGA), parport,
> serport, mouse, floppy (720k) and harddisk (20M). Takes PS/2
> keyboard and mouse. Three 8 bit ISA slots.

Ah - the 70 is basically an updated AT-286 but with the MCA bus rather
than the ISA bus.

> It's even got ROM Basic. Found out when I messed with fdisk and
> forgot to put a floppy in the drive.

It's an IBM product, so that's to be expected.

> No ESDI hard drive, no MCA slots, just a plain XT.

When it comes to hard drives, there's no such thing as a "plain
XT". From experience, I've seen XT's with MFM, RLL, ESDI, (E)IDE and
SCSI hard drives, and as the original XT didn't even have a hard drive
interface, it's anybody's guess which is fitted.

I've just had a look on IBM's website, and the Model 30 reference
diskette is for a 286 based system. I know that some of the PS/2 range
were available with different processor options, and it's more than
possible that the Model 30 is one such, but there's precious little
about that machine on their website, so that didn't help.

>> Probably only the same problem I'm having - I don't have the
>> foggiest how to calculate the figure to use on the mkfs line.

> I guessed a block to be 1024 bytes, 2 sectors. The figures I
> got doesn't divide evenly with figures from fdisk. :-(

> A look in the source /include/linuxmt/fs.h leads me to believe
> that the blocks are 1024 bytes long. But I'm not fluent in C so
> I can't be certain.

The term "block" is misleading in this sense as it's used in two totally
different ways in ELKS, so let me clarify:

1. To the low level media drivers, a block is a physical sector, and
in ELKS, that's always 512 bytes.

2. To the high level FS subsystem, a block is the fundamental unit
for organising data on permanent storage, and is almost always
2 sectors (1,024 bytes) although it can be more.

The problem I have is that the blocks specified by fdisk are 512 byte
sectors, at least in theory, but this figure bears no resemblance to the
figure one has to specify to the mkfs command.

What I'd love to see is the ELKS mkfs command work the same way as the
Linux one, where one just specifies the partition and it works out the
size for itself. In reality, there's no reason that I can think of why
it should need the size specifying, other than that the programmer was
either a tad idle or a tad careless.

> I'll just have to wait until it's fixed. 5.5MB is plenty to
> play with for the time being. :-)

True.

Best wishes from Riley.