Model A, OS 0.1 and disc interfaces

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Coeus
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Model A, OS 0.1 and disc interfaces

Post by Coeus » Tue Dec 19, 2017 6:41 pm

Does anyone know if the Model A with any OS, or the Model B with OS 0.1 ever had a disc interface?

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BigEd
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Re: Model A, OS 0.1 and disc interfaces

Post by BigEd » Tue Dec 19, 2017 6:55 pm

I vaguely recall that OS 0.1 couldn't support disk, and it was almost a violation of the advertising or trading rules at the time. Which is to say, perhaps Acorn should have offered a free upgrade to the OS, but they didn't. I wrote to them at the time, with a poorly-worded letter which failed to get me the free OS upgrade I wanted.

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Re: Model A, OS 0.1 and disc interfaces

Post by crj » Tue Dec 26, 2017 11:54 pm

Well, you had to add some hardware and a filing system ROM in order to use disc; as long as they make it available and never quote you a price which excludes it, why is it deceitful if you also need an updated OS?

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Re: Model A, OS 0.1 and disc interfaces

Post by Coeus » Thu Dec 28, 2017 11:07 am

So I think what you are saying here is that the Model A can have the 8271 installed but OS 0.1 doesn't handle paged ROMs so you can't get the DFS ROM to drive it.

On the question of free replacement ROMs the case for a disk upgrade could be handled by nequiring if you have OS 0.1 when you go to but a disc upgrade and, if you do, including the OS 1.2 ROM as part of the package. That doesn't solve the issue of someone wanting to run other software from ROM.

I wonder what most people did. Were the OS 1.2 ROMs available to buy or did they get EPROM copies from their cloest mate who has access to an EPROM programmer?
Last edited by Coeus on Sat Jan 06, 2018 1:19 pm, edited 1 time in total.

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Pernod
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Re: Model A, OS 0.1 and disc interfaces

Post by Pernod » Thu Dec 28, 2017 11:56 am

You would typically take your machine to your local Acorn dealer to get the OS upgraded, for a nominal charge.
- Nigel

BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, BeebZIF, etc.

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Re: Model A, OS 0.1 and disc interfaces

Post by crj » Thu Dec 28, 2017 3:53 pm

I've never seen such a machine, but I got the impression early Beebs had the OS in four 4K EPROMs in the four sockets intended for sideways ROMs, and BASIC in a 16K ROM in the OS socket. Very early machines had BASIC in four more 4K EPROMs on a carrier board, but I assume they did things the way they did because BASIC stabilised enough to be committed to ROM earlier than the OS.

That means an upgrade from 0.1 to 1.2 involves moving BASIC as well as exchanging the OS EPROMs for a ROM, plus changing a bunch of links, which might be why they were happier if a dealer did it.

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Re: Model A, OS 0.1 and disc interfaces

Post by Coeus » Thu Dec 28, 2017 4:13 pm

crj wrote:I've never seen such a machine, but I got the impression early Beebs had the OS in four 4K EPROMs in the four sockets intended for sideways ROMs, and BASIC in a 16K ROM in the OS socket. Very early machines had BASIC in four more 4K EPROMs on a carrier board, but I assume they did things the way they did because BASIC stabilised enough to be committed to ROM earlier than the OS.
Interesting how things have changed. I assume this was all because 16K EPROMs were either not available or very expensive. I do remember BITD that keeping your ROM to 8K rather than running to 16K was significant if you were proposing to use EPROM but that would have been a year or two down the line compared to when they were finalising the OS and BASIC.

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Re: Model A, OS 0.1 and disc interfaces

Post by crj » Thu Dec 28, 2017 5:13 pm

Coeus wrote:I assume this was all because 16K EPROMs were either not available or very expensive.
That's my assumption, too.

Plus, they might well have already had 4K EPROMs in the parts bin and/or supply chain because of the System and Atom ranges.

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Re: Model A, OS 0.1 and disc interfaces

Post by IanB » Tue Jan 02, 2018 6:19 pm

The very first disc interface upgrades came with a free copy of OS 1.00 (not OS 1.20) in two 8K EPROMs on a small board, sometimes referred to as a "butterfly" board as the layout of the EPROMs vaguely resembled wings. That could be upgraded for free to OS 1.20 in ROM when it was released.
Eprom boards.jpg
The top one is a "butterfly" board
The bottom one is the board used when both OS 0.10 and BASIC were supplied in 4K EPROMs (mentioned by crj)

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Re: Model A, OS 0.1 and disc interfaces

Post by crj » Sat Jan 06, 2018 4:36 am

Woah, fascinating! I mean, it's pretty much exactly what I imagined, but I'd never seen a photo of one before.

Main difference from my imagination: those red sockets. (-8

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Re: Model A, OS 0.1 and disc interfaces

Post by steve3000 » Sun Jan 07, 2018 7:50 am

By chance last night I came across an old Acorn ROM in my collection, labelled B02. Bit of investigating and it's OS 0.1. Popped it in the beeb, to find it didn't support BASIC 2, so I dug out BASIC 1 and tried again. This worked, now *FX0 reports "OS 0.1 EPROM" (which is slightly odd, because it's a mask ROM for sure).

Anyhow the beeb has 8271 interface fitted and DNFS ROM present...this all worked fine under OS 1.2, but as expected, I can confirm that DFS ROM wasn't detected with OS 0.1 in place.

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