It is well known that NTSC ColecoVision consoles have, what many find to be, an irritatingly long duration set for displaying the title screen of games. Well, that is those games that use the "COLECOVISION PRESENTS" BIOS title screen function - quite a few do not, e.g. AtariSoft games. It is also well known that the title screen duration of CBS PAL-SECAM ColecoVision consoles was set much shorter.
It has also been documented that changing the value of byte 0x196A in the ColecoVision BIOS changes the duration that the "COLECOVISION PRESENTS" title screen is displayed.
This got me curious. What is the relationship between title screen duration (seconds) and the byte value of 0x196A? Well after much testing and measurement I figured out that it's a simple linear relationship that applies to both NTSC and PAL-SECAM ColecoVisions:
Title Screen Duration (seconds) = Decimal Value of 0x196A x 0.55
So, by way of an example. The value of byte 0x196A in the standard NTSC BIOS is 17h. This is equivalent to 23 in decimal and this multiplied by 0.55 equals 12.65 seconds. This is in fact higher than the all of the durations I have seen people report over the years which have been 7, 10 and 12 seconds. The mind boggles how anyone could have thought the delay was as low as 7 seconds, let alone 10 seconds.
As for CBS PAL-SECAM ColecoVisions, the value of byte 0x196A is set much lower at 06h. This is 6 in decimal and multiplied by 0.55 equals 3.3 seconds, over 9.3 seconds less than an NTSC unit ! ! !
The one exception (that I know of) is if 0x196A is set to zero. I was thinking that this would simply bypass the title screen but instead it does the opposite and permanently displays it. No amount of waiting (or anything else for that matter) will coax the ColecoVision to move to the game select screen.
To make things easy, here's a simple lookup table that lists the hex value of 0x196A and the title screen duration:
A surprising observation is that the title screen duration varies amongst the CV emulators even when they're all using the default NTSC BIOS. I measured these duration's:
- blueMSX v2.8.3 = 12.65s (correct)
- CoolCV v0.6.6 = 5.50s (way too low)
- ColEm 4.6 = 10.70s (low)
There's something strange going on with CoolCV and ColEm so I'm going to follow this up with the developers.
I have way to much time on my hands