BBC B Issue 3 O.S. 1.0

discuss both original and modern hardware for the bbc micro/electron
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e668ecp
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BBC B Issue 3 O.S. 1.0

Post by e668ecp »

The old BBC that i've fixed the memory fault on has O.S. 1.0 mounted on a daughter board as two chips, LO and HI; see image. I've never seen this before.

I'e tried swapping the daughter board / basic roms for later versions but the BBC refuses to start.

Can it be done, if so how?
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IanB
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Re: BBC B Issue 3 O.S. 1.0

Post by IanB »

OS 1.00 on the butterfly board was shipped with the early disc upgrade kits and upgrading to the OS1.20 ROM should be just a simple swap with no changes required.

However, the early versions of the butterfly boards had thick pins that plugged into the BBC's OS ROM socket and that damaged the socket so a normal ROM wouldn't work and you had to replace the OS ROM socket to fix it so that might be your problem. Later versions of the butterfly board had turned pin extensions that didn't damage the BBC OS socket.
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tricky
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Re: BBC B Issue 3 O.S. 1.0

Post by tricky »

Maybe not damage, but stretch ;)
Still, if you have one, you could try your new ROM in a turned pin socket in the old socket.
e668ecp
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Re: BBC B Issue 3 O.S. 1.0

Post by e668ecp »

Bingo! I'd not thought of that, is the OS 1.2 rom available as an SSD?
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flaxcottage
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Re: BBC B Issue 3 O.S. 1.0

Post by flaxcottage »

- John

Check out the Educational Software Archive at www.flaxcottage.com
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Bobbi
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Re: BBC B Issue 3 O.S. 1.0

Post by Bobbi »

How do the MOS versions line up with the board issue numbers, out of curiousity?

What would be the original MOS for a issue 3?
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flaxcottage
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Re: BBC B Issue 3 O.S. 1.0

Post by flaxcottage »

My original Issue 3 came with OS 0.1 in ROM.
- John

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Bobbi
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Re: BBC B Issue 3 O.S. 1.0

Post by Bobbi »

What versions exist? Just 0.1, 1.0 and 1.2?
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1024MAK
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Re: BBC B Issue 3 O.S. 1.0

Post by 1024MAK »

Most are here ;-)

Mark
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Bobbi
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Re: BBC B Issue 3 O.S. 1.0

Post by Bobbi »

Am I correct in believing 1.2 is the most recent that works in a Model B?
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1024MAK
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Re: BBC B Issue 3 O.S. 1.0

Post by 1024MAK »

Yes.
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jgharston
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Re: BBC B Issue 3 O.S. 1.0

Post by jgharston »

No.

OS 1.23 works in a BBC B.

And there's an OS 1.5x floating around somewhere.

OS 2.xx will work in a BBC B, but will be unable to access the shadow screen.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.32
(C) Copyright J.G.Harston 1989,2005-2020
>_
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JasonStonier
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Re: BBC B Issue 3 O.S. 1.0

Post by JasonStonier »

jgharston wrote:
Mon Oct 12, 2020 12:08 pm
OS 1.23 works in a BBC B.
Is there any advantage to putting OS1.23 in a B?
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1024MAK
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Re: BBC B Issue 3 O.S. 1.0

Post by 1024MAK »

JasonStonier wrote:
Mon Oct 12, 2020 12:15 pm
jgharston wrote:
Mon Oct 12, 2020 12:08 pm
OS 1.23 works in a BBC B.
Is there any advantage to putting OS1.23 in a B?
It will make fault finding more difficult if you suffer from a DRAM chip failure...

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Bobbi
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Re: BBC B Issue 3 O.S. 1.0

Post by Bobbi »

How so? I am curious.
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1024MAK
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Re: BBC B Issue 3 O.S. 1.0

Post by 1024MAK »

Bobbi wrote:
Mon Oct 12, 2020 7:01 pm
How so? I am curious.
See the changes text which says that it assumes 32k bytes of RAM. OS 1.20 (Acorn’s last mainstream version for Model A and Model B machines) tries to work out if it’s running on a 16k or 32k RAM machine and posts the appropriate message. By trying different positions of link S25, it’s possible to select which bank of 16k DRAM chips is used for the 0x0000 to 0x3FFF part of the 6502 memory map. If there is good working RAM in this area, the machine will start up as a working 16k machine (as if it was a Model A).

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Bobbi
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Re: BBC B Issue 3 O.S. 1.0

Post by Bobbi »

Ah, good to know! Thanks!
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Re: BBC B Issue 3 O.S. 1.0

Post by daveejhitchins »

Well, that's an easy fix . . . If you have problems: swap the ROM back to the earlier version :wink:

Dave H.
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