[DMDX] Preparation delays Hi. I am using the following rtf to present backwardly masked bitmaps to  participants on a slave computer.      ! This vm provides 4 memory buffers. 0 ; 0 g "4e" %2 / g "4a" %59 /; 0 g "6a" %2 / g "6a" %59 /; ! etc. Continues for 58 subsequent trials. 0 "The End.  Thank you for your participation."; The slave receives a TTL signal through the games port from a master  computer that is running VPM. VPM is being used to deliver acoustic startle  probes, and record physiological signals (eg, EEG, facial EMG & HR). The problem I have encountered is that there is an inconsistent delay  between the receiving of the request (TTL, or keyboard activated on slave)  and the presentation of the bitmaps. The inconsistent delay makes it  impossible to time acoustic probes from the master computer. Preparation A  for bitmaps vary between .10 to 1500ms, whereas preparation B is steady  between 40 and 50ms. I'm presuming that Prep A relates to the loading of  the *.bmp files, and hence is processor intensive. If anyone is aware of how to make this delay relatively constant (i.e.,  Prep A), or how to reduce it to a minimum, I'd appreciate it if you would  let me know. It may be necessary to establish a feedback signal from the  slave to the master PC, but I am unsure of DMDX's ability in this area, and  would like some advice. Best Regards, Julian Simmons. ===================================================== Julian Simmons School of Behavioural Science Department of Psychology University of Melbourne Victoria 3010 Australia. jgs@unimelb.edu.au                  j.simmons1@pgrad.unimelb.edu.au Ph: +61 3 8344-0326     Fax: +61 3 9347-6618    Mobile: 0411 161 769 =====================================================