Stuart Posted May 17, 2018 Share Posted May 17, 2018 So why 10.7 MHz? That's also the frequency for the VDP, so are they driving both the CPU and VDP from the same crystal? Is running the CPU at this slower speed just a cost-cutting measure to save a separate 12 MHz crystal, or is there some benefit somewhere? Quote Link to comment Share on other sites More sharing options...
+mizapf Posted May 17, 2018 Author Share Posted May 17, 2018 The same situation can be found in the 99/8. Also, the 99/2 has no VDP, just a simple controller. Yes, they share the same clock. Quote Link to comment Share on other sites More sharing options...
fabrice montupet Posted May 17, 2018 Share Posted May 17, 2018 The TI-99/5 has two crystals: One for the CPU 9500 and one for the VDP, as the 99/4 &4A. 1 Quote Link to comment Share on other sites More sharing options...
kl99 Posted May 18, 2018 Share Posted May 18, 2018 Meanwhile, some numbers. CPU clock 10738635 Hz internally divided by 4 is 2684658.75 Hz. This yields a cycle time of 372.487 ns (a bit longer than the 99/4A with 333 ns). The outer loop is 400, the inner loop is 65536 iterations, which is a total of 26214400 iterations, each with one memory access. If there is a wait state of one cycle for each memory access, this means 9.76 seconds, which is roughly that what I found as the time difference on the MAME emulation. If it was a late decision change and you are saying that having this correct is key for Tape loading/saving to work it could mean that the real machine is actually running in a wrong speed for it to work. I mean that the routines were not adapted yet in Rom. At least we have to consider this option. Quote Link to comment Share on other sites More sharing options...
+mizapf Posted May 18, 2018 Author Share Posted May 18, 2018 The good thing about emulation is that you can play "what if...". But I already tried it, and this did not work for me either, so my hope was to get a reference point with the real machines to figure out what goes wrong. Quote Link to comment Share on other sites More sharing options...
fabrice montupet Posted May 18, 2018 Share Posted May 18, 2018 The TI-99/4B has also two crystals. Quote Link to comment Share on other sites More sharing options...
Casey Posted May 26, 2018 Share Posted May 26, 2018 Not to hijack the technical discussion, but did TI ever produce any prototype cartridges for the 99/2 to go along with it when it was planned for release? How about the "demonstration cassette" that the 99/2 Getting Started manual makes reference to? Just kind of curious to know how close TI was to having a fully released product when the 99/2 was cancelled. Quote Link to comment Share on other sites More sharing options...
fabrice montupet Posted May 26, 2018 Share Posted May 26, 2018 (edited) There is at least one cartridge known to exist. The one presented at the 1983 CES. Here is a picture: Its name is "Learn to Program". A second cartridge has been introduced: "Learn to "Learn to program Basic". I have never see it. For the expansion devices, many were already available thanks to the Hexbus port. Edited May 26, 2018 by fabrice montupet 1 Quote Link to comment Share on other sites More sharing options...
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