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 [ 2 posts ] 
 8-bit age display adapters (aka 80-column cards)? 
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Joined: Thu Jan 17, 2013 4:38 pm
Posts: 44
Once upon a time there were Apple II, C= 64, CP/M and probably more machines that could be expanded with what was often labeled 80-column cards.

Did these have any chips on common, or were any of them homemade brews of some kind? Especially interested in items with bitmap capabilities, even more so if colour.


Tue May 06, 2014 11:56 am

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1632
My guess would be that most of those expansion busses were not much different from the raw processor bus from the MPU - perhaps with some buffering or some decoded control lines. One notable exception was the Tube as seen in Acorn's BBC machines, which was somewhat like a memory mapped peripheral: a ULA chip faced both the host and the slave machine busses, and offered interrupts so that neither side has to poll for activity. There were 8 internal FIFOs so that messages could be posted from one side to the other without needing to handle them byte-by-byte on both sides at the same time. That gave 4 channels in each direction, for distinct purposes such as stdin/stdout, OS calls, block transfers. The original Tube connector is a 40-pin umbilical but it can be run over 20-pin cable.

See http://www.apdl.co.uk/riscworld/volume9 ... /index.htm and http://www.sprow.co.uk/bbc/hardware/armcopro/004.pdf

Jonathan Harston has defined a byte-serial transport for the Tube protocol, and there's a perl version of the host code. The slave code generally fits in 2k of ROM and exists for 6502, z80, 6809, NS32016, ARM and PDP-11 at least. See http://mdfs.net/Apps/Emulators/Tube/ and http://mdfs.net/Software/Tube/Serial/ and http://www.stardot.org.uk/forums/viewto ... 12&p=58863

Cheers
Ed


Wed May 07, 2014 9:02 am
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