Date   : Mon, 07 Oct 2002 19:57:45 +0100
From   : "Richard Gellman" <splodge@...>
Subject: Re: speed

>Is it possible to speed a BBC micro up. Perhaps by disabling certain events
or by any other method?.

If you have the skills and the patience...

You can desolder the 6502, and put in a 65C102. You will need pinouts for
this, as I *think* they have different pin configurations.
Then you need to rewire the entire clock system for a 6Mhz CPU clock. The
BBC Micro uses a system of 2Mhz dropped to 1Mhz for accessing certain
devices.
The 1Mhz speed will have to be respected, as the hardware in question cannot
deal with higher speeds. Then you need to rewire the multiplexing
hardware for the CRTC. The BBC Micro multiplexes by alternating cycles
between the CPU and the CRTC for access to the screen memory. This needs
to be changed to allow the CPU more cycles to access the memory while still
retaining 1 cycle for the CRTC. (Note: The Master 128 has all this in a
propietary CRTC MUX chip). If you do all that, you'll get a faster BBC
Micro. However with the drop to 1Mhz for hardware access on a regular basis,
its
debateable as to whether you will actually see much of a speed increase.

Or, if you're really ambitious, you could try and build your own board based
on a 6Mhz 65C102 system, and "emulate" some devices....

-- Richard