Re: Filesystem creation

Riley Williams
2002-05-14T06:42:30Z

Hi Dan.

On checking, I see that mislabelled them slightly, so here's the
corrected version...

>> To be accurate...
>>
>> 1. The original IBM PC was supplied with a CASSETTE drive as
>> standard. 160k floppies were a very expensive optional extra
>> as you had to buy not only the drive, but also an interface
>> card and an operating system to boot from them, all sold as
>> separate items. Hard drives were NOT supported, and it was
>> not possible to add support for them as the BIOS didn't have
>> the ability to hook extensions in.

> Sure it is, what are you talking about? It wasn't until the AT was
> introduced that hard drives were BIOS supported. Before that, the
> controller card had it's own BIOS on it, and the system BIOS just
> scanned for adaptor BIOSes before trying to boot. I've used both MFM
> and SCSI in origional PCs.

The problem with your quote above is quite a simple one - the original
IBM PC didn't scan for adapter BIOSes, so was VERY limited in what
expansion one could add to it. That was an oversight by IBM's engineers
as they provided the slots for plugging in expansion cards, but forgot
to allow for BIOS support for those expansions. The BIOS included the
ability to boot from floppies as standard, but that was about all.

This was the original version of the original IBM PC, with a fixed 16k
of RAM that couldn't be expanded on the motherboard.

>> 2. The original IBM PC/XT was supplied with a "new upgraded" 180k
>> floppy drive as standard, and as an option, these could be
>> replaced with a 360k drive for an extra £275. I remember paying
>> the extra when this wmachine was top of the range.

> I thought single sided drives were only offered in the origional PC
> - the real old ones that only had 16-64K of RAM optional. Don't know
> for sure on that one though I guess.

This is the one I mis-labelled - this is the revised original PC, where
the RAM could be expanded from the supplied 16k up to 64k, and NOT the
PC/XT as I originally labelled it. Yes, I had one, and I paid the extra
for the floppy drive.

This is where Bill Gates made his famous "Nobody will want more than
64k" comment - see below for his later comment.

>> 3. The "Revised" IBM PC/XT was supplied with dual 360k floppies
>> as standard, and one of them could be replaced with an MFM
>> hard drive - originally 5M in capacity, but those were replaced
>> with 10M ones within a month, and the MFM interface was replaced
>> with an RLL one about a month later to increase the capacity.

> Yup, the "eXtended Technology" :)

As stated, this was the original IBM PC/XT - I stand corrected. This
also allowed for up to 256k of RAM to be fitted to the motherboard, and
was where the clones started to appear. Unlike IBM's offering, the
clones offered 512k of RAM on the motherboard as standard.

I also omitted a couple here, so here we go...

3a. The "revised IBM PC/XT" was the original IBM PC/XT with the
onboard RAM capacity upgraded to 640k when the clones were all
offering 512k on the motherboard. The clones promptly followed
and allowed 640k as well.

It was at this point that Bill Gates made his famous "640k will
be enough for anybody" comment

3b. The IBM PC/XT-286 was supplied with a 286 processor running at
6 MHz (compared to the original 4.77 MHz) and was available in
two versions, one with dual 1200k floppy drives, the other with
a 360k floppy drive and a 15M hard drive.

>> 4. The IBM PC/AT was supplied with a 20M hard drive as standard,
>> as well as the 286 processor and various other "standard extras"
>> as IBM referred to them.

> And it ran at a whopping 6MHz too :)

Exactly the same as the PC/XT-286 that preceded it. I liked the "standard
extras" phraseology myself...

>>> I've got an 8086 based PS/2, a 25 I believe.

>> That agrees with IBM's website.

> Good, then I'm actually remembering something right today!

You do indeed. IBM's website labels the Model 25 as being 8086 based,
and the Model 30 as being 80286 based. My Model 70 is listed as being
available in either 286 or 386 based versions, and I have the 286
version here.

>> If you still have it handy, could you try the latest images out and see
>> whether it works now. If not, would you be willing to help explore why
>> it doesn't work so we can fix the problem?

> Well, it's not handy, but I still have it. If I stumble across it I'll
> grab it and see if it works or not. I'm having a hard enough time just
> getting a boot disk made and installed in my IBM XT (eXtended Technology :).

Could you advise what the problem is with doing that? The various Linux
distributions all supply rawrite.exe which can write the image out to
floppy under MS-DOS so the procedure isn't hard.

> You know, it's a little off the subject, but what would really be
> handy is a little C compiler that ran under ELKS. It wouldn't need
> to be able to compile the OS, just something we could use to write
> little programs. Just a thought, it would give me a little
> motivation to use the OS anyway :)

We would all love that. However, according to Alan Cox, BCC is slightly
too large and as a result won't compile itself, although the assembler
and linker both compile fine to run under ELKS.

There's one or two tweaks I would like to see done to BCC anyway, so I
may soon be looking into this and seeing if I can get bcc to compile
itself. No promises though...

Best wishes from Riley.

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