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The Video Display Processor (VDP) of the TI-99/4A was capable of displaying 32 hardware sprites. These sprites were unusable with the default, built-in BASIC that TI provided. However, an enhanced BASIC (Extended BASIC) was available that provided much needed support for the TI's hardware. Including 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? Was this another ploy by Texas Instruments to cripple what home users could do in an attempt at selling more "TI Branded" software?

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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 2 KiB for screen handling (including 80 bytes line buffer) (*1), leaving a bit less than 12 KiB for programm and data.

For Extended BASIC it is essential to be able to support programs of similar size as with TI-BASIC - this includes the ability to load (old) TI-BASIC programs. Thus memory requirement should at best not exceed what has been set by TI-BASIC. At the same time it needs memory to hold additional data like:

  • Sprite attributes table
  • Sprite motion table |
  • Some system data area
  • An extended crunch buffer
  • And a new edit buffer for the improved editor

All of this would have end up at ~500 Bytes less memory available. By reducing the the character table (*2) as well as the sprite tables this was reduced to ~300 bytes. In addition some data areas (like line symbol table) wouldd be moved into RAM expansion if present.

So while it seams little, it's safe to assume that they tried hard to reduce the memory footprint.

Was this another ploy by Texas Instruments to cripple what home users could do in an attempt at selling more "TI Branded" software?

Another ploy? Like a secret conspiration? Serious, why on earth should TI do so?


*1 - Plus another ~2KiB for file buffers when a disk unit is installed (more with number of files set above 3)

*2 - Extended BASIC reduced the available glyphs by 16 to 30..143.

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    "Why on earth should TI do so?" I don't think it happened in this instance. But companies have built systems intentionally using underpowered specs and limited expandibility, not just to save on costs but to establish "product differentiation" and limit the expected lifetime of the product. Similar things happen on the software front. I'm not passing judgement on the ethics of such practices, just stating that it does happen. The business side of consumer electronics often leads to decisions that make no sense to end users. – RichF Jan 12 at 1:34
  • Agree that sometimes there's deliberate underperformance of lower-priced products - but for that to apply here, there surely would have needed to be a higher-priced version that allowed 32 sprites. Was there? – another-dave Jan 12 at 1:42
  • Beside, who would pay more for a meager 4 sprites more ... when 28 ist already way past what any other system offered. – Raffzahn Jan 12 at 10:18
  • @RichF Except, the statement isn't about companies making diverse offerings around the same architecture (just think Apple and Macintosh Machines of the 90s), but TI with it's sole 99/4 offering and Extended BASIC offering 28 sprites over zero of the build-in BASIC. – Raffzahn Jan 12 at 10:21

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