hoopstar wrote:So at which model/service number did Holden switch to 4.2Mhz?
That's something I'd like to know myself. My suspicion is that ECU's compatible with $12P firmware are 2.1MHz and PCM's compatible with $11P firmware are 4.2MHz. The guys who have access to the source code would know the answer. If these ECU/PCM were all running at 2.097MHz, we wouldn't have everyone concerned about EPROM speeds, because 250ns or better is pretty much anything you can lay your hands on.
I dont think anything runs at 4.2mhz. 11P and 12P both run at 2mhz, and the flash pcms run at 3.41mhz. Its been a while since ive switched on my VT bench but if it works i'll see if I can measure the clock speed there.
So, my bench is working fine. I measured the switching speed of the CE line on the memcals/roms/flash as I could see that was cycling at clock speed and I could get a good stable measurement on it. I got 2.08Mhz for the '808 and the '424 (MAP PCMs), 3.15Mhz for the VS and VT (MAF PCMs) and 3.41Mhz on the VX/VY (Flash PCMs).
So ... the newer EPROM-based PCM's have 1.5x the MCU speed of the old ones, not 2x ...
OK then, assuming there's no added glue logic to mess up the calculations (unfortunately, I can't find a schematic for the newer PCM's), with a 10ns margin, these will require an EPROM (or alternative memory type) with an access time of 135ns or better.
Im not sure how you calc that but sounds about right. So plus tollerances for reality were back to about 120ns borderline or better, and we can get away with a bit more on the older ones. Makes sense.
