22 votes

Why did the TI-99/4 have two databuses?

According to Wikipedia, The unusual architecture of the 99/4 series is documented to be due to the failure of the 9985, an 8-bit processor which was being created specifically for the machine. When ...
Stephen Kitt's user avatar
19 votes

Why did the TI-99/4 have two databuses?

Now given that the TMS9900 has a 16 bit databus, it seems to me that they could have put all memory and all periphery on that bus. It would have saved the cost of the multiplexor, and made the ...
Raffzahn's user avatar
  • 223k
17 votes

Why did Extended BASIC on the TI-99/4A only allow 28 of the 32 sprites?

The VDP area for the Sprite Attributes Table is 0x0300 to 0x037f. That is 128 bytes, which is 4 bytes per sprite. Each sprite entry in this table has the sprite's X/Y position, color, index to the ...
Dan's user avatar
  • 366
10 votes
Accepted

What was the purpose of GROM (vs ROM) in the TI-99/4a?

However, the TI cartridges could also contain a different type of ROM called "GROM". Which I believe was "Graphics ROM". Jup, although, it wasn't really related to graphics at all. More due the fact, ...
Raffzahn's user avatar
  • 223k
9 votes

Why did the TI-99/4 have two databuses?

If you look at the description of the databus multiplexer e.g. here The TMS9900 being a 16-bit processor, it has 16 data lines and 15 address lines. However, only the console GROMs (>0000-1FFF) ...
dirkt's user avatar
  • 27.3k
9 votes

TI-99 display interference

CRT screens used varying magnetic fields (from wire coils carrying a sawtooth-wave electrical signal) to deflect an electron beam and scan it across the screen. These fields extended outside the TV to ...
jeffB's user avatar
  • 2,826
8 votes

TI-99 display interference

Unless you had dozens of different types of TV's with a controlled test, it's hard to really quantify how good that RF modulator was (or how bad). Also, you said you don't remember what the third ...
cbmeeks's user avatar
  • 8,531
8 votes

Is it possible to use a TI-99/4A cassette cable with Digital Audio devices?

Any cassette tape system which can utilize a standard cassette tape recorder can be plugged into any audio device, with sufficient quality, and will work. You can record saved files with any audio ...
Tim Locke's user avatar
  • 4,811
8 votes

Why did the TI-99/4 have two databuses?

So my question is why the TI-99/4 had these two databuses. Why not put everything on a single databus? The TMS9900 CPU only has three on-chip registers, none of them being so much as an accumulator. ...
RichF's user avatar
  • 9,336
5 votes
Accepted

How to fix a TI99/4a membrane keyboard?

According to jdv's answer to another question, cotton swabs and isopropyl (rubbing) alcohol will do the trick. Try to keep the alcohol away from plastics, use it sparingly and be gentle when you rub ...
wizzwizz4's user avatar
  • 18.6k
5 votes

How to fix a TI99/4a membrane keyboard?

A pink pencil eraser is a reasonable contact cleaner for this sort of thing. Just scrub the black dots a bit and see if they will respond to softer pressure.
silver's user avatar
  • 71
5 votes

Audio cassettes on TI-99

I always thought this was unique to the Atari until around 1984/5 when I saw a TI-99 at the local mall doing the same thing Well, similar but different (*1), as the Atari mixes the AUDIO-IN signal ...
Raffzahn's user avatar
  • 223k
4 votes

TI-99 display interference

You seem to be describing a TV that wasn't fine-tuned to the Channel 3 or Channel 4 VHF signal coming from the TI-99/4A. Any computer or game using the RF modulator style of connection could suffer ...
uruiamme's user avatar
  • 141
3 votes

Is it possible to use a TI-99/4A cassette cable with Digital Audio devices?

I have tried to save or load from a smartphone and PC. These don't record well. However the audio file from tape may be processed on PC. Audiotap and CS1er are examples of software for the TI. I have ...
dciurchea's user avatar
3 votes

Why did Extended BASIC on the TI-99/4A only allow 28 of the 32 sprites?

But for some reason, you could only work with 28 sprites instead of the maximum of 32. So, what was the reason behind this? One reason may have been space. Of the 16 KiB RAM, build-in TI-BASIC uses ...
Raffzahn's user avatar
  • 223k
2 votes
Accepted

TI-99/4a RF modulator, fuzzy video

While not directly answering my own question, this is the solution I ended up doing: I just ended up buying a composite adapter, which works great. I decided against opening up the RF modulator, as I ...
Keltari's user avatar
  • 503

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