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#110208 - 07/07/17 04:17 PM Re: BBC Tube WIP [Re: Pernod]  
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crazyc Offline
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Makes sense to halt the cpu during refresh. Interesting that PCS0 is connected to INT1.

#110554 - 08/09/17 03:01 PM Re: BBC Tube WIP [Re: Pernod]  
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Pernod Offline
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And now have the Casper 68000 2nd Processor running. The software list bbc_flop_68000 is now supported with this.
[Linked Image] [Linked Image]


BBC Micro
#110558 - 08/09/17 06:18 PM Re: BBC Tube WIP [Re: Pernod]  
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Nice work! I'm glad to see the BBC finally hitting its potential in MAME.

#110559 - 08/09/17 08:06 PM Re: BBC Tube WIP [Re: Pernod]  
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Not many more 2nd processors left to add now, and will be enquiring how best to implement the 32016 CPU sometime soon.

Whilst many of these 2nd processors were potentially great for business and educational use, not much software was ever produced specifically for them. And being targeted at businesses meant software was lost rather than being found 20 years later and imaged by home users.

The 6502 2nd Processor can run an enhanced version of Elite, faster and more colours due to having more RAM available for video. Am hoping no-one posts Elite to the Gotta-rum-'em-all thread until I get the video issues fixed to really show this off.


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#110615 - 08/17/17 12:40 PM Re: BBC Tube WIP [Re: Pernod]  
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Pernod Offline
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There's also an internal board, the Cumana 68008 2nd Processor.
Details: http://chrisacorns.computinghistory.org.uk/8bit_Upgrades/Cumana_680082ndProcessor.html
Schematics: https://acorn.huininga.nl/pub/docs/...umana_68008BBCUpgrade_CircuitDiagram.pdf

This doesn't use any of the standard ports but inserts into the 6502 socket with the 6502 then moved to the board, so will need a new 'internal' slot. The 68008 has full access to all ram/rom and devices seen by 6502. How can I map the 6502 program space from 0x2000 -> 0xffff into the 68008 program space at 0x0000? The 68008 has it's own 512K ram at 0x80000. I could re-map all bbc banks and devices into the 68008 space but would prefer to just tell it to use same space if possible.

The board will run OS9, and have a collection of floppy images for this device to be softlisted.


BBC Micro
#110616 - 08/17/17 12:54 PM Re: BBC Tube WIP [Re: Pernod]  
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Your best bet is to grab the 6502's address_space and then issue read_byte/write_byte to it from 68008 read/write handlers. Look at the dma_r() / dma_w() functions in src/devices/bus/a2bus/a2bus.cpp. The Apple II's Z80 and 6809 cards use that mechanism to run CP/M and OS-9.

#110617 - 08/17/17 02:19 PM Re: BBC Tube WIP [Re: Pernod]  
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Pernod Offline
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That's exactly what I was looking for, thanks.


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#110628 - 08/20/17 01:56 PM Re: BBC Tube WIP [Re: Pernod]  
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Pernod Offline
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Now have the 80186 co-processor running in the Master 512 (bbcm512). Had this working a couple of weeks ago but been having trouble with floppy formats to get GEM loading.

[Linked Image] [Linked Image] [Linked Image]

The machine is not yet complete as it still needs a mouse device. It's supposed to be capable of reading various PC floppy formats and running some PC software so will try hooking up the ibm5150 software list to check compatibility.

The issue with floppy formats was due to a subtle bug in the wd177x_dsk helper. The number of sectors per track is fixed to that of the first image loaded, and could be the cause of other MT issues reported that use this helper. Need to get this stuff cleaned up and submitted in the next couple of days.

I've been using READ8_DELEGATE instead of read8_delegate(FUNC, which is preferred?


BBC Micro
#110939 - 10/01/17 07:57 PM Re: BBC Tube WIP [Re: Pernod]  
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Pernod Offline
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The 80286 2nd processor was never commercially released, and is only found in a few examples of the ABC 310 that exist. What we know is that it used the same boot ROMs that were found in the later Master 512, and had 1MB RAM. All photos out there seem to be of the same board and no schematics have been found so a little reverse engineering of the boot code was required. The boot ROM detects whether it is running on 80186 or 80286 and acts differently accordingly.

There is no known software specifically developed for the ABC 310 so am running the Master 512 System disk which shows it running on the 80286 and behaves differently from the Master in my previous post.

[Linked Image] [Linked Image]

Last edited by Pernod; 10/01/17 07:58 PM.

BBC Micro
#110941 - 10/01/17 08:32 PM Re: BBC Tube WIP [Re: Pernod]  
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crazyc Offline
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Seems rather pointless since the 80186 was just as fast per processor cycle as the 80286 and it only supports 1MB of RAM anyway. Maybe if it was AT compatible enough to run Windows in standard mode it would make more sense.

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