Manufacturer: Quicksilva

 The QS Sound Board is based around a AY-3-8910 Programmable Sound Generator IC, which provide 3 independent tone channels, 1 noise channel and 2 general purpose 8-bit I/O ports. These features are accessed through 16 8-bit registers. The QS Sound Board accesses the AY-3-8910 using two memory mapped I/O ports at addresses $7FFE (32766) and $7FFF (32767). Port $7FFF selects the sound chip register to access and port $7FFE is used to set the data for the selected register. Using memory mapped I/O allows the sound board to be controlled from BASIC by poking to these two memory locations.

The Quicksilva documentation for the sound board claims it is driven by a 1.78977 MHz clock (which happens to be half the NTSC 'colour' crystal frequency of 3.579545 MHz). Since the circuit for the sound board takes the clock signal exposed at the edge connector of the ZX80 or ZX81 and halves it, this would imply that the clock frequency of the ZX80/81 was 2 x 1.78977 = 3.57954 MHz. This is wrong. The ZX80/81 is clocked at approximately 3.21 MHz and so results in the sound board being clocked at approximately 1.605 MHz.

  7FFFh.W   PSG index (Quicksilva QS Sound board)
  7FFEh.R/W PSG data  (Quicksilva QS Sound board)

Supported by:
  Cosmic Guerilla (Quicksilva)
  Croaka (aka Hopper) (Quicksilva)
  Defenda (Quicksilva)
  Space Invaders
  Asteroids (Quicksilva) (also supports PSG reg 15 as alternate joystick)
  Scramble (Quicksilva)
PSG reg 15: used by asteroids (as OUTPUT, probably as pull-up)


The "QS Sound Board" For The ZX80/81 

Play tunes in three-part harmony on 
your ZX80 or ZX81! Based on the 
extremely versatile AY-3-8910 sound gen- 
erator chip, the QS Sound Board features 
complete software control of the frequency 
and amplitude of three independent output 
channels as well as an envelope shaper 
and noise channel. 

The QS Sound Board can produce fairly 
accurate scales over a 5 octave range, 
from C at 32.7Hz to B at 989Hz with a 
minimal error of +/-0.5%. Because of the 
limitations of the power supply, no amplifier 
or speaker has been fitted to the QS Sound 
Board. Instead, the three channels have 
been mixed together and taken to a 3.5mm 
jack socket via a preset volume control, 
therefore an external amplifier and speaker 
are needed. The Radio Shack 277-1008 is 
recommended. 

If you wish to use more than the onboard 
memory with the QS Sound Board, you 
will need the QS Motherboard which allows 
the 16K RAM pack to be used in con- 
junction with the QS Sound Board and 
one other board. 

The QS Sound Board also features two 
8 bit input/output ports taken to a 16 pin 
i/c socket for easy connection to external 
control functions via ribbon cable. 

The prices for the above products are: 

QS Sound Board £28.00 
QS Motherboard £13.00 
QS Sound Board & Motherboard £38.00 

Quicksilva are at 95 Upper Brownhill Road. 
Maybush. Southampton, Hants., England.