Author Topic: A new z80 calc... in color?  (Read 60797 times)

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Offline Adriweb

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Re: A new z80 calc... in color?
« Reply #150 on: November 11, 2012, 05:28:26 pm »
Is a z80 processor going to be enough for driving a color screen? Or will we see some not-shitty screen drivers (at last :O)? I wonder how fast the processor is going to be...
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Offline DJ Omnimaga

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Re: A new z80 calc... in color?
« Reply #151 on: November 11, 2012, 05:37:22 pm »
Yes, I got confirmed it's a z80.

More details/answers are coming "soon" and HD photos in early January.


edit : lolz dilbert.

I assume that they're gonna use a modified Z80, because according to Runer112, a Z80 cannot run at more than 25 MHz.

Has anyone tried a TI-Nspire CX with Nover setup at 25 MHz CPU speed? When you select stuff in menus, the frame rate is atrocious. TI is gonna have to do some heavy optimizations if they plan to use a 25 MHz processor with a 320x240x16bpp (or even 8bpp) screen, unless the calc somehow has some sort of extra processor just for video.

Offline aeTIos

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Re: A new z80 calc... in color?
« Reply #152 on: November 11, 2012, 05:38:37 pm »
is an ez80 also considered a z80? since that can run at 50 MHz.
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Offline DJ Omnimaga

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Re: A new z80 calc... in color?
« Reply #153 on: November 11, 2012, 05:40:23 pm »
From what I have read on IRC, TI doesn't own any rights on eZ80 or something, unlike the Z80, so if they need an eZ80 that is much faster than anything already available on the official sites, then they will not be able to create their own.

50 MHz might be just enough, though. The PRIZM runs at 58 MHz and both the menu and home screen still runs at very decent speed. Graphical stuff is only slow because Casio failed hardcore at implementing it.
« Last Edit: November 11, 2012, 05:41:59 pm by DJ_O »

Offline aeTIos

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Re: A new z80 calc... in color?
« Reply #154 on: November 11, 2012, 05:41:24 pm »
Oh. Well in that case maybe they use 2 Z80s?
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Offline willrandship

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Re: A new z80 calc... in color?
« Reply #155 on: November 11, 2012, 05:53:45 pm »
The ez80 IIRC isn't actually z80 architecture. It has a backwards-compatible z80 mode, similar to how the GBA has a backwards-compatible GBC mode, except built into the processor.

They probably have a single z80 along with a decent display driver. A display driver renders the "not powerful enough for the screen" argument moot, since then the calculator wouldn't even need to store the current screen image in RAM.

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Re: A new z80 calc... in color?
« Reply #156 on: November 11, 2012, 05:58:53 pm »
So the screen driver is what processes stuff on the screen? I just don't see how a 15 MHz z80 will be able to produce a decent framerate with such a large screen. The TI-84 C  screen is 200 times more data to transfer than the TI-84 Plus SE LCD. The only way they can achieve it is by optimizing to death and only update the necessary parts of the screen at once (for example if the cursor is moved around). But how slow will RecallPic get?

Offline willrandship

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Re: A new z80 calc... in color?
« Reply #157 on: November 11, 2012, 06:06:03 pm »
A screen driver is a separate chip, dedicated to running the screen. It would handle the framerate issues and such. The only worry would be the calculator's speed at pushing new images in, so you could even do it with the old 6 mhz CPU. It would just be slow.

The non-color ti-84s and ti-83s already have screen display drivers. They're why we have to sync our grayscale Axe routines (The screen ALWAYs updates at 60hz, regardless of CPU speed.)

RecallPic would probably take a few seconds. So would storepic. They would also take ridiculous amounts of space.
« Last Edit: November 11, 2012, 06:06:42 pm by willrandship »

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Re: A new z80 calc... in color?
« Reply #158 on: November 11, 2012, 06:08:17 pm »
A screen driver is similar to a graphics card, just a little slower :p
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Re: A new z80 calc... in color?
« Reply #159 on: November 11, 2012, 06:08:40 pm »
I see. Actually now I tried my PRIZM at 14.5 MHz and my Nspire at 23 (lower than that it said warnings in Nover) and the Nspire had a quite fast cursor movement speed. The PRIZM gave 2 FPS for typing calculations, but the menu had about 4 FPS.

Hopefully they do it right. If the processor is just a Z80 with a decent display driver, do you think the battery will eat batteries much slower than the Nspire CX?

Offline DrDnar

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Re: A new z80 calc... in color?
« Reply #160 on: November 11, 2012, 10:02:11 pm »
Here's my professional opinion: A Z80 is certainly fast enough to handle simple color graphics. The biggest bottleneck in current Z80-series games is the LCD interface. The worst feature is the need to wait several clock cycles after every write. It's just long enough to be a major bottle neck, but not long enough to do anything really useful. However, even if the new driver requires no wait states, a larger screen will still take a lot more CPU power to draw graphics for. The lack of wait states could well be completely offset by the need to compute more graphics data. We'll really need to pray for 25 MHz speed.

How the driver implements color access will have an effect on speed. If it's one nibble per pixel, then graphics access will still be slightly awkward. Unfortunately, any higher resolution precludes a fully memory-mapped solution. The Z80 can directly access up to 65536 bytes of memory, but a 320x240 display has 76800 pixels. Chances are, we'll still have to deal with an LCD driver, and we definitely won't be able to make ready use of a back-buffer for graphics. However, if the LCD driver requires no wait-states, it may actually be an advantage: the LCD driver can handle the multiplication to calculate RAM addresses for us.

We also must wonder whether there will be emulation for the old LCD driver.

Edit: Let me just clarify: If TI optimizes their code (e.g. no wait states, less LCD updating, plotting for every other x, better floating-point routines) and raises the CPU speed, they could still get a reasonable graphing speed. However, a 320x240 display has more than ten times as many pixels as the current 96x64 display, so games may have a tough time drawing full-resolution graphics in real-time.

Another point to consider is how TI will be adding more memory. TI can easily add more memory without significantly reducing profit-margins, but they can't add more flash memory in a manner that current software will be able to access without changes. There is no more room in the memory map for more flash memory, but they could easily add up to 2 MB of RAM. If they want to add more flash, perhaps they will use another set of ports to page the additional memory; or perhaps they will switch to a NAND, and we'll have to contend with reading byte-by-byte from an internal buffer on the NAND; or perhaps they'll completely break the current system.

Here's something bad to consider: as long as they're completely reworking the ASIC, they might as well remove the ability to unlock the boot code. No doubt, with great color comes great restrictions on programmer freedom. But that's why we have people like BrandonW. We are firing up our oscilloscopes! We are reading our disassemblers! Native code! will! be! ours!

But I still think it'll actually turn out to be an Nspire in disguise.
« Last Edit: November 11, 2012, 10:48:25 pm by DrDnar »
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Offline _Nicco_

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Re: A new z80 calc... in color?
« Reply #161 on: November 11, 2012, 10:05:24 pm »
I was planning on getting an 84+SE or an 83+SE but now I think I'll wait.
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Offline ralphdspam

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Re: A new z80 calc... in color?
« Reply #162 on: November 11, 2012, 10:24:45 pm »
I wonder if they'll use the 16-bit I/O port addresses (with undocumented opcode behavior) to implement the color screen.  Hopefully their ASIC provides full backwards compatibility for ports $10 and $11.
« Last Edit: November 11, 2012, 10:24:59 pm by ralphdspam »
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Offline DJ Omnimaga

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Re: A new z80 calc... in color?
« Reply #163 on: November 11, 2012, 10:28:33 pm »
I wonder if they could manage to fix the RAM Clear issue after crashes by storing a backup of the user RAM into a different RAM area, so when the calc is reset, the last backup from when the calc was last turned OFF is restored from there?

Offline DrDnar

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Re: A new z80 calc... in color?
« Reply #164 on: November 11, 2012, 10:52:45 pm »
I wonder if they could manage to fix the RAM Clear issue after crashes by storing a backup of the user RAM into a different RAM area, so when the calc is reset, the last backup from when the calc was last turned OFF is restored from there?

Omnicalc already has that feature for TI-83+SEs and TI-84+(SE)s with all 128 K of RAM.
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