Sellam Ismail wrote: I'm guessing this was a way to sell /4 mainboards still in inventory after the /4A was introduced, among other things. The mainboard might have been redesigned specifically for the Insight, though, which is one of the things I'd like to find out. Yup.

Sellam, Actually, the /4A used a different video chip. The one used in the original /4 was a TMS9918, the /4A used the TMS9918A, which added a 192x256 pixel bit mapped mode. Later, Frank (Who subscribes to the 99/4A mailing list, too, since I still have my original 99/4A) Sellam Ismail wrote: > From my understanding, the TI-99/4 and 99/4a are the same save for the > keyboard. > Are there any motherboard differences? I wouldn't think so. > Sellam Ismail Vintage Computer Festival

Sellam Ismail wrote: Different VDP's, as Frank mentioned, and different ROMs. The 4A adds lower case ASCII characters, etc., The /4 has an equation calculator mode missing from the /4A. There are other minor differences that mean some /4A cartridges and disk software don't work on a /4. Don't recall if it's the same PWB. I have one of each machine apart somewhere around here and can look if you're interested. You're right, though, there is no substantial difference between them. It's entirely possible there's a /4A board in the Insight, just more likely a /4, in my view. If it isn't something else entirely. It's possible if not likely the terminal has its own ROMs, regardless. By the way, I'm hearing of yet another prototype machine that has an 80-col display. jbdigriz