This is something interesting for friends of the A3000. I did this
Turbo Upgrade quite a long time ago, and it makes your A3000 (if still
ARM2 powered) as fast or faster than an A3010/A3020/A4000. The speedup
is most noticeable in large screen modes like 800x600 (with a VIDC Enhancer).

The hardware was designed by Ingmar Weigel quite some time ago. I have
slightly patched some of the software.

The build instructions are in German (see Turbo Doc!), so here is a short
version in English:
- solder the components onto the PCB (see the "Hardware" drawfile in
  !Turbo.Extras)
  40 MHz oscillator gives you 13.3 MHz, 36 MHz oscillator results in 12 MHz
- desolder IC47 (74HC04, in south east position) from your A3000 motherboard
- put a socket where IC47 was
- fit TurboA3000 PCB to the IC47 socket
- remove jumper LK 28
- connect upper pin of LK 28 with the TurboA3000 PCB (see drawfile)
- remove the keyboard controller chip (Intel 8051) from its socket and
  carefully bend pin 18 upwards. Put it again into the socket and solder
  a cable from pin 18 to the TurboA3000 PCB (see drawfile)
- solder a cable from IOC Pin 47 (e.g. from upper pin of R30) to the
  TurboA3000 PCB (see drawfile)
- put your A3000 together again - it should work now with the same speed
  as before. Start the !Turbo application to switch to Turbo mode!

Experiences:
- socket the osci and try out 36 MHz and 40 MHz variants. 40 MHz variant
  usually only works with 70ns RAM/4 MB extensions, and you might need
  to slow down ROM access speed (see SlowRom BASIC file).
- 60ns RAM is needed for 48 MHz (resulting in 16 MHz system speed), but
  not every ARM2 works at that speed
- double-check that your harddisc interface keeps your data intact when
  running in turbo mode!
- this upgrade also works together with typical VIDC enhancers

See the directory !Turbo.Extras.patched for slightly more advanced
software to automate ROM access speed slowdown and auto-fix a list
of given screenmodes.

Be extra careful when soldering/desoldering stuff!

No guarantees that this really works.

All the hard work was done by Ingmar Weigel. I only wrote these english
instructions and contributed the patched software.

Have fun,
Steffen Huber
http://www.huber-net.de/
