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Acorn System WIP #113654
07/06/18 12:15 PM
07/06/18 12:15 PM
Joined: Apr 2012
Posts: 217
UK
Pernod Offline OP
Senior Member
Pernod  Offline OP
Senior Member
Joined: Apr 2012
Posts: 217
UK
In recent weeks I've been implementing the full range of Acorn System machines. These are basically a collection of Eurocards each for CPU, RAM, VDU, etc. on an Acorn Bus backplane.

Acorn System 2 (acrnsys2):
This system consists of 6502 CPU, 8K RAM/ROM, cassette, and 40 column VDU cards. This is a cassette only (Cos) machine. It should also contain a 4K BASIC ROM but is currently MIA, though I hope to find this during an Acorn meetup at Centre for Computing History in September.
[Linked Image]

Acorn System 3 (6502 CPU) (acrnsys3):
There are very few floppy images out there for these machines, though this appears to be the System 3 Utilities disc containing Floating Point BASIC to run from RAM.
[Linked Image]

I've made each card a slot device, and this System 3 has 2x8K Static RAM boards, 40 column VDU card, and a FDC. Each 8K card also has two ROM slots for extensions such as BASIC, Econet. I currently only have Econet ROMs which will be softlisted for these slots.
[Linked Image]

The memory boards have links that determine where RAM/ROM is addressed.
[Linked Image]

Acorn System 3 (6809 CPU) (acrnsys3_6809):
This was already in MAME but has been rewritten as a collection of slot devices, and added a FDC to the system to run FLEX. I've renamed a6809->acrnsys3_6809 to match other machines in the range. The 40 column VDU card cursor was incorrect, and is now rendered by the 6845. The FLEX floppies are currently MIA but again hope to get them imaged in September.
[Linked Image]

Acorn System 4 (acrnsys4):
Basically the same as System 3 but with more slots and comes with 2 floppy drives as standard.

Acorn System 5 (acrnsys5):
The System 5 was the last in the range and had some improvements with a 6502A (previous were 6502), 32K RAM boards, 80 column VDU, etc. It seems it was also used to develop what became BBC BASIC, and we have an image of it.
[Linked Image]

The 32K RAM boards also have links to select where they are addressed. The 80 column card can also be re-mapped for use in a 6809 system.
[Linked Image]

The System 5 would usually contain an Econet card and be used as a File Server, and this is handled too.
[Linked Image]

The Acorn Atom has two Acorn Bus expansion ports (internal/external) so am also moving it's floppy implementation to slot devices, and adding other expansions.


BBC Model B, ATPL Sidewise, Acorn Speech, 2xWatford Floppy Drives, AMX Mouse, Viglen case, etc.
Re: Acorn System WIP [Re: Pernod] #113655
07/06/18 12:50 PM
07/06/18 12:50 PM
Joined: May 2004
Posts: 856
Germany
D
Duke Offline
Senior Member
Duke  Offline
Senior Member
D
Joined: May 2004
Posts: 856
Germany
Very nice. It's great to see those systems implemented properly.

Re: Acorn System WIP [Re: Pernod] #113925
09/10/18 03:00 PM
09/10/18 03:00 PM
Joined: Apr 2012
Posts: 217
UK
Pernod Offline OP
Senior Member
Pernod  Offline OP
Senior Member
Joined: Apr 2012
Posts: 217
UK
I've now got a couple more 6809 ROMs that require different configurations of the cards. The current machine acrnsys3_6809 requires the vdu40, fdc, and 3x8k cards. The 8k cards have configuration options to specify where the RAM is mapped.

One of the new ROMs is for use with the 80 column vdu80 card (replacing vdu40) and requires RAM at different locations to the current acrnsys3_6809. Is there any way of overriding default configuration options of slot devices in machine_reset (or similar)? So in this case I'd want to swap the vdu40 for the vdu80 card. The vdu80 card has configuration options to set it's IO mapping and by default it's configured for the 6502 in machine acrnsys5.

I could add the ROM as a new machine with the correct cards inserted, but would still need to manually configure the RAM mapping and vdu80 IO.


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

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