Pictures
April 2008: 6502 in patchable stripboard on double socket stack, allowing us access to the clock.
April 2008: clock buffer experiments with 6502. Shortly after this we decided to buy a half-dozen 65816 parts.
May 2008: Level 0 stripboard - 65816 with clock buffer running on host clock
Sep 2008: Our Boot ROM code running in Rombo on the L0 board. Rombo is Rich's EEPROM emulator and programmer, controlled by i2c.
Sep 2008: Rombo gets an improved cable arrangement. USB-i2c adapter in plain view - i2c is one of Rich's favourite technologies, and with the USB adapter we can drive it from almost any host machine.
Sep 2008: Our Boot ROM code running in Rombo on L0 board. The Beeb has a UHF modulator and composite out. It has several bit-mapped graphical modes, but boots into a 25x40 teletext (character-generator) mode.
Oct 2008: The L1 board - verowire on perfboard. 65816 with memory, address latch, clock buffering. Clock switching is to be off-board.
Nov 2008: The Level 1 board verowired and installed.
May 2009: L1 board with clock switch and plain board as a triple-decker.
May 2009: clock switch with delay lines on top of the triple-decker. We didn't expect to need delay lines - we still intend to run with an asynchronous clock - but at this point we were using a switchable delay line to explore the timing.
Jan 2009: L1 board with clock switcher on breadboard. This was a milestone: a beeb running at 4MHz with128k RAM and a 16bit processor.
Jun 2009: L1 board clocked at 8MHz, using our MCUMall CPLD as a divide by two from a 16MHz taken from the beeb.
Dec 2009: L1b PCB - two sided, 10mil width and spacing, no resist. We had several design ideas using a 44pin CPLD, but went for 84pin for the additional flexibility. We have half a dozen surface mount bypass caps, but otherwise it's all through-hole (and socketed)
Dec 2009: L1b running, probably only at 4MHz with first CPLD revision. See the clock taken from beeb's video circuit. Note that we have a socket for a crystal oscillator, a socket for an i2c EEPROM, and a 20-way expansion connector which is intended to be TUBE-capable.
See our Picasa web gallery for the original full size pictures [Broken archive! Unhappy face.]