Jump to content
IGNORED

TI-99/2 questions


mizapf

Recommended Posts

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?

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

There is at least one cartridge known to exist. The one presented at the 1983 CES. Here is a picture:

ti992hcm.jpg

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 by fabrice montupet
  • Like 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...