DACS App Note

DACS DSP Memory Buffer Usage Versus Signal Objects Inserted (#14)

The purpose of this app note is to inform the user of the amount of DSP memory buffer used when various signal objects are inserted. The 3 most common model builder versions, 3.04E, 3.06C and 3.08, along with the currently available types of DSP boards, are covered.

DSP memory buffer is consumed when Play/Record sounds are used or when radios are added and the system is used in a DIS environment. The term "radios" used here refers to both transmitter and receiver objects. It is recommened that the user check the amount of memory buffer consumed periodically when developing a model. Models whose memory buffer usage approaches 100% should be streamlined or have its model iteration rate reduced.

Available buffer memory is displayed on the "Waveform DSPs" "Memory" window. The number under "buffer" is the percentage of buffer memory consumed when a given signal object is added. A number of 6.8 means that 6.8% of the buffer's memory has been used. Not all signal objects consume buffer memory. The ones that do are listed below.

Available buffer memory size can be determined several ways. The first and easiest is to look at the "Waveform DSPs" "Memory" page and look for "Memory =". "Memory = 512" is for large memory and "Memory = 128" is for small memory. Only later versions of Model Builder 3.08 and up support this feature. The second way to determine memory size is to physically examine the DSP board memory ICs. This is not a recommended manner as it would require the user to open the chassis and violate the warranty. It is also not necessary for earlier versions of Model Builder because the memory consumption is the same for the Signal Objects inserted. On the DSP board ICs U7, U8, U9, U10 will be 32 pin DIPs for large memory and 28 pin DIPs for small memory. The 4 memory ICs are located in the upper left hand corner of the board.

Model Builder 3.04E

  • Sample Rate=8 KHz
  • Highway Width=2
  • DSP v4.88, Driver v3.05
  • 80 MHz boards
    fifo=2048 Mips=20.2
  • 50 MHz board
    fifo=2048 Mips=12.7
  • Model Rate=24 Hz
  • Sound Block Size=8

80 MHz
(large mem.)
% used
80 MHz
(small mem.)
% used
50 MHz
1 Play Sound 6.2 6.2 6.2%
2 Record Sound 6.3 6.2 6.2
3 Radio 3.1 3.1 3.1
3.1 Receiver 2.3 2.3 2.3
3.2 Receiver Tacan 2.4 2.4 2.4
3.3 Receiver DME 2.3 2.3 2.3
3.4 Receiver ADF 2.3 2.4 2.4
3.5 Signal pdu 2.3 2.3 2.3
4 Transmitter 0.7 0.7 0.7
4.1 Jammer 0.8 0.8 0.8
4.2 Vor 0.8 0.8 0.8
4.3 DME 0.8 0.8 0.8
4.4 Tacan 0.8 0.8 0.8
4.5 Vor DME 1.5 1.5 1.5
4.6 Vor Tac 1.6 1.6 1.6
4.7 Ndb 0.8 0.8 0.8
4.8 Ndb cw 0.7 0.7 0.7

Model Builder 3.04E

  • Sample Rate=8 KHz
  • Highway Width=2
  • DSP v4.88, Driver v3.05
  • 80 MHz boards
    fifo=2048 Mips=20.2
  • 50 MHz board
    fifo=2048 Mips=12.7
  • Model Rate=24 Hz
  • Sound Block Size=8
80 MHz
(large mem.)
% used
80 MHz
(small mem.)
% used
50 MHz
1 Play Sound 6.2 6.2 6.2%
2 Record Sound 6.3 6.3 6.3
3 Radio 3.1 3.1 3.1
3.1 Receiver 2.3 2.3 2.3
3.2 Receiver Tacan 2.4 2.4 2.4
3.3 Receiver DME 2.3 2.3 2.3
3.4 Receiver ADF 2.4 2.4 2.4
3.5 Signal pdu 2.3 2.3 2.3
4 Transmitter 0.7 0.7 0.7
4.1 Jammer 0.8 0.8 0.8
4.2 Vor 0.8 0.8 0.8
4.3 DME 0.8 0.8 0.8
4.4 Tacan 0.8 0.8 0.8
4.5 Vor DME 1.5 1.5 1.5
4.6 Vor Tac 1.6 1.6 1.6
4.7 Ndb 0.8 0.8 0.8
4.8 Ndb cw 0.7 0.7 0.7

Model Builder 3.08

  • Sample Rate=8 KHz
  • Highway Width=2
  • DSP v4.88, Driver v3.10
  • 80 MHz board with large memory
    fifo=2048 Mips=20.2 Mem=512
  • 80 MHz board with small memory
    fifo=1024 Mips=20.2 Mem=128
  • 50 MHz board
    fifo=1024 Mips=12.7 Mem=128
  • Model Rate=24 Hz
  • Sound Block Size=8
80 MHz
(large mem.)
% used
80 MHz
(small mem.)
% used
50 MHz
1 Play Sound 1.1 6.8 6.8%
2 Record Sound 1.2 6.9 6.9
3 Radio 0.5 3.4 3.4
3.1 Receiver 0.5 2.6 2.6
3.2 Receiver Tacan 0.4 2.6 2.6
3.3 Receiver DME 0.5 2.6 2.6
3.4 Receiver ADF 0.4 2.5 2.5
3.5 Signal pdu 0.5 2.6 2.6
4 Transmitter 0.1 0.8 0.8
4.1 Jammer 0.1 0.9 0.9
4.2 Vor 0.2 0.8 0.8
4.3 DME 0.1 0.9 0.9
4.4 Tacan 0.2 0.9 0.9
4.5 Vor DME 0.3 1.7 1.7
4.6 Vor Tac 0.3 1.7 1.7
4.7 Ndb 0.1 0.9 0.9
4.8 Ndb cw 0.2 0.8 0.8