The Acorn BBC Micro came into being when Acorn won the contract from the BBC to produce a home computer that the BBC could use to promote technology and computing at home, school and in the work place. Acorn won this contract, mainly on the strength of their first Acorn Atom computer which had been fairly successful. The BBC models A and B were very successful with hundreds of British schools adopting them for what were to become classics, such as Granny's Garden, or Pod. BBC's were also popular amongst the more affluent enthusiast who wanted more than a Speccy could deliver, with it's built in BBC BASIC, and assembler in ROM, and massive expandability to boot. The Master and Master Compact were later introduced with a 3.5" disk drive and although not so popular, still sold well. Acorn then broke the connection with the BBC, and skipped a generation from 8 bit to 32 bit, years ahead of their time, to give us the ARM system we have today.
These
emulators were provided on the Applications 2 disk of every Acorn, up until
the RISC PC. Hurriedly developed by Acorn ready for the Archimedes
launch back in 1987, in order to tempt schools to dump their old 8 bits
and move up to the Archimedes, because, " you can run all your old
software too!". This was never really true, since a fair amount of
BBC software had some form of copy protection, there was also the copyright
grey area of making a copy to use on an Archimedes, as well as the more
technical fact that 65Host wasn't up to the job. 65Host and it's sister
emulator 65Tube, although reasonable emulations, were by no means perfect
as many users found to their disappointment when many games such as the
classic elite simply wouldn't work. On the other hand, in many cases 65Host
was able to run the relatively undemanding educational software and text
based applications and was used for many years at my school.
65Host is still freely available, but unfortunately it doesn't work on a RISC PC without being patched, and the command *CACHE I being entered if you have a StrongARM in order to allow the program to run. Pcr13 by Jan De Boer allows 65Host to work on a StrongARM without the cache being disabled (so you can have a 50MHz 6502Em). More recently, 65Host has become more important in the world of emulation as the only program within which the sacred BBC B system ROMs are allowed to be distributed. This has led to many people on other platforms wanting to get hold of 65Host in order to extract the ROMs for their own emulators (illegally).
65Host v1.62 (1992)
Speed Rating: ARM
3 
StrongARM
Note: needs patch to work on a RISC PC
65Host available from
here
Pcr13
65Host
patch
6502Em
is written entirely in ARM code by Mike and Anne Borcherds, and is published
by Warm Silence Software.
Rather than just emulate one of the BBC models, 6502Em can emulate the
Electron, BBC model A, B, Master and Master Compact, (but not the original
Atom) provided that is you can get hold of the system ROMs for each system.
65Host is distributed with the package, and it is a simple matter to run
a program and extract the BBC B ROMs to be able to run 6502Em.
A small BASIC program is also provided to be run on the other original
systems, and will save their ROMs to disk, to be copied to within 6502Em.
6502Em is a much better quality emulator than 65Host, and can emulate nearly all aspects of the original hardware, and is probably as good a BBC emulation as there'll ever be. The classics such as Elite can all be run on it fine, indeed the purpose box in the information window reads, "purpose: to play elite", and it's true! 6502Em is of course fully StrongARM compatible.
The emulator can be bought for £15 + VAT (or a discount if you buy it with Z80Em), and WSS will also supply a tape interface and hardware to allow software to be more easily copied across from the BBC to the Acorn.
6502Em v2.10
Speed Rating: ARM
3 ARM 6
ARM 7 StrongARM
6502Em
page
6502Em
online manual
Michael Foot's BeebIt emulator of the 32K BBC Model B is the first fully freeware BBC emulator for the Acorn. Although 65Host was widely distributed it was still copyright Acorn and was by no means perfect in its compatibility. 6502Em, though a very good emulator was unfortunately commercial so BeebIt has to be the people's champion as far as BBC emulators go for the RISC OS machine.
Unfortunately the people's champion can't really cut it with the other two as far as speed's concerned, and it's not surprising really, since while both 65Host and 6502Em are written in highly optimised ARM assembly, BeebIt has been written in C. Some of the original code was based on David Devenport's BeebInC emulator for the PC, but all the old code has now been removed and updated by Mike. The emulator is just about usable but could do with a lot more optimisations, so if you don't own a StrongARM it's probably not worth it. On a StrongARM BeebIt now runs faster than the original Beeb and will be needing a speed limiter for future versions.
With the latest release there have been a couple of bugfixes to things like the SBC opcode, and the sideways RAM, keyboard handling, interrupts, and with various other improvements many popular games such as Exile, Skirmish, Psycastria, Strykers Run work correctly and others like Rev are nearly there. Interlaced frames are now also supported which provides a slight speed up on lower end machines but affects the clarity of the display. The screen plotting routines have been rewritten in assembly for added speed, as well as the odd instruction opcode (such as JSR). Things are improving quickly now with simple things like fixing it so that Econet detection returns disabled now allows Dr. Who and the Mines of Terror to run. Mike is now turning to adding sound emulation to the emulator though as any emu author knows this is a difficult and complex part of the coding and something which will take a while to be adequate for release. If things continue at this pace a much more compatible and very usable free emulator that can compete (for StrongARM owners at least) with 6502Em may be on the cards.
BeebIt v0.05 (31 May 1999)
Speed Rating: ARM
3 
ARM 6 
ARM 7
StrongARM
BBCConv
Lots of BBC software is available to download from the BBC Lives, but this is archived in a perculiar format. Gareth Moore has written BBCConv to allow these files to be extracted on an Acorn and the games played on 6502Em.
If you are having trouble extracting the ROMs from 65Host, the RipROMs code by Darren Salt and John Doe allows you to 'rip' the BBC B's BASIC and OS ROMs directly out of 65Host (version 1.61 only) and save them for use with other emulators, that don't provide them.
RipROMs
(7Kb Sparkive)
BBCConv
(19Kb ZIP)
Technical details
CPU - 6502A running at 2MHz (65C12 in Master 128)
Display - Screensizes 640*256 @ 1bpp (2 cols) 320*256 @ 2bpp (4
cols) 160*256 @ 4bpp (8 real cols and 8 flashing cols) teletext 40*32 chars,
8 cols. No hardware sprites.
Sound - 76489 (4 channels, one of which is just for white noise)
RAM - 32k standard (model A 16k), more can be added instead of sideways
ROMs (of which video RAM can be between 1k and 20k)
ROM - 32k standard (16k OS, 16k BASIC), max 272k (16k OS + 16 sideways
ROMs of 16k)
Screen 6845 + Acorn designed ULA + teletext chip
RS423/casette 6850
two 6522s, one to control keyboard, sound, joystick fire buttons,
CRTC 50Hz interrupt, light pen interrupt, ADC interrupt
and the second to drive the printer and user port.
ADC 7002 (joystick)
Disc chips 8271 or 1770
reference - Michael Borcherds, author of 6502em
Extras:
ImageDFS
Year
2000 fix for BBCs
Software:
BBC lives
- The best BBC page, loads of technical info, emulators (for all platforms),
utilities and loads of software.
BBC
emulators and video game software
6502Em
game compatibility list.
Watford
Archive of disk images
8 bit Nirvana
Recommended software:
Elite, Chuckie Egg, Pod, Granny's Garden, Exile, Firetrack, Joust,
Planetoid, Revs, Mr Ee, Snapper, Chuckie Egg, Thrust, Zalaga, Stryker's
Run, Repton 3, Boffin 2, Citadel, Bonecruncher, Codename:Droid, Spycat
