Well, one of my friends has a Ti-83+, you know, no USB cable. I was wondering if I could connect to his calc using that cable.

No. There's the silverlink, which is USB to 2.5mm, but that's for connecting a calculator to a computer. You can link two calculators with a simple 2.5mm link cable.

Oh, okay. Got it.

He says he has the link cable, but needs to find it...

Can you put DCS on a Ti-83+?

Yes. Doors CS runs properly on the TI-83+, TI-83+SE, TI-84+, TI-84+SE, TI-Nspire with TI-84+ keypad, and all known emulators. There's also a TI-83 version of Doors CS 5.x.

I thought the Ti-83+ had only like 9561 bytes of ROM?
At least thats what it looked like in his memory menu...

The calculator comes preloaded with a bunch of apps that most people never use. You can free up a lot of ROM by deleting some of them.

So, how much ROM can you actually use on the Ti 83+?

It appears to have 10 user-accessible Flash pages (160 kB), based on what Wikipedia and Datamath say. I don't have a calculator handy, so can't confirm that for myself, but it sounds accurate.

Yes, that's correct. 9K left sounds like all but one page used, plus some extra stuff archived. You can delete plenty of the preloaded apps.

Now, why can't the Ti-84+ graph 3D graphs?

Well, the math subsystem wasn't designed to evaluate functions with an X and Y. And besides, 3D wasn't in the scope of the calc's purpose.

Indeed. It's a combination of the hardware being too slow to rotate graphs quickly (using the TI EOS, anyway), and TI wanting to save more features to be TI-89-exclusive.

There's the Graph3D app for 3D graphing on the 83+/84+. It's somewhere on ticalc.org

Aye, and it works very nicely. That's why I felt it necessary to clarify that only something using TI's EOS would likely be too slow for a highish-resolution 3D graph.

So if one were to modify the Ti84_Plus.8xu, then you could make it graph 3D stuff natively? I do know that the Ti-89/Titanium has a higher resolution (and faster processor? more RAM/ROM?) than the Ti-84+.

Good luck with that.

If I'm not mistaken, the hardware math functions on the Motorola 68k are a lot more robust than on the z80, not that it's hard to do. The z80 only has hardware support for the addition of two 8 bit registers at any given point, whereas the 68k has hardware support for addition, subtraction, multiplication, and division. Being able to do hardware multiplication alone will speed up any graphing application by a large factor. I'm also pretty sure that the 89 has a memory mapped screen buffer, so you aren't limited by the time the driver takes to push things to the LCD. So, while the 'speed' of the z80 on a TI-84 is technically faster at 15MHz, the hardware surrounding the TI-89 68K is just vastly superior.

You can also add (with or without carry) two 16-bit registers and subtract (only with carry) two 16-bit registers on the Z80. But otherwise you are correct. The 68k has many more registers and can add and subtract (with or without carry) up to 32 bits at a time (registers or memory), multiply two 16-bit registers (I think later models in the 68k family can do full 32-bit multiplication), and 16-bit division.

On the other hand, the Z80 has a parity flag while the 68k does not. So parity calculation is slower on 68k. But almost everything else is faster on 68k.

Just goes to show that CPU clock speed != CPU performance.

That's Detached Solutions's Graph³, and from what they say on the project page it's actually faster than the TI-89 3D grapher. So yeah, basically what AHelper was saying