Author Topic: TG 16-bit processing...  (Read 922 times)

Press_Run

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TG 16-bit processing...
« on: November 28, 2008, 12:53:51 AM »
There's no doubt the Turbo-Grafx/PC-Engine was the one of the first console to provide 16-bit graphics yet had 8-bit processing heart. I came across this interesting article months back.

http://www.gamefaqs.com/console/turbo16/file/916398/5708

According to it, TG was able to pull off its 16-bit graphics by utilizing two 8-bit cores. Can anyone substantiate this as I'm hardpressed to believe a single 8-bit core could have done all that.

SuperDeadite

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Re: TG 16-bit processing...
« Reply #1 on: November 28, 2008, 01:06:58 AM »
I'm not authority, but I thought the PCE was an 8-bit CPU, with a 16-bit graphics chip of some kind.  (I could possibly be 100% wrong though)
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Tatsujin

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Re: TG 16-bit processing...
« Reply #2 on: November 28, 2008, 01:59:31 AM »
right you are.
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Necromancer

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Re: TG 16-bit processing...
« Reply #3 on: November 28, 2008, 02:18:38 AM »
Dual core processing in 1987?  Now that's Turbo Power!  :lol:

That faq is incorrect.  There's only one CPU (HuC6280), and it's single core and 8-bit.  The PCE/TG-16 pulls off 16-bit graphics (er, grafx) with two 16-bit GPUs: the HuC6260 color encoder and the HuC6270 video display encoder.  Furthermore, the specs for the CD-ROM are all jacked up.  It doesn't have a 16mhz 65802 processor, though that would certainly be interesting (it's similar to the SNES CPU, though far speedier).  The RAM listed for Arcade Cards is also wrong, as they add 16Mb (17.5Mb for the Pro card) to the existing RAM, for a grand total of 18Mb (2.25MB).
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nat

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Re: TG 16-bit processing...
« Reply #4 on: November 28, 2008, 03:14:28 PM »
You must also remember that while there was only one 8-bit CPU, a lot of the work was offloaded on the two 16-bit graphics chips. Also, the CPU operated at 7.16Mhz (or something close to that), which was only a little slower than the CPU in the Genesis and many times faster than the CPU in the SNES.
« Last Edit: December 03, 2008, 12:34:44 PM by nat »

spenoza

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Re: TG 16-bit processing...
« Reply #5 on: December 03, 2008, 11:29:07 AM »
That 7 mhz stuff doesn't mean anything unless you're comparing identical, or very similar, CPUs. Why else would a 2 ghz AthlonXP chip have been able to whip a 2.5 ghz Pentium 4? While it's possible the TG and SNES CPUs are somewhat similar, the Genesis CPU is a very different beast. Thus mhz is not a useful point of comparison. MIPS or actual mathematical performance data is a better comparison.
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Michael Helgeson

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Re: TG 16-bit processing...
« Reply #6 on: December 03, 2008, 12:24:34 PM »
I think number crunchers here before have done so already, and found the PCE Hu cpu to be faster over all then the Snes cpu. Regardless of that even, the proof is in the games, where as you do see the PCE move alot of sprites alot faster over all in everything, and you hardly ever have any real slowdown on the PCE versus the Snes on comparable titles like Gradius 2 PCE versus Gradius 3 Snes, or Rayxanber 3 versus Super R-type on Snes.

Game makers them selves from most companies complained that the Snes cpu was just a tad too slow at times and far less efficient for their liking compared to TG/PCE and Genesis cpus. It took them quite awhile to really get a grip and overcome alot of the slow down probs in the games Snes wise, and they never did fully, no matter what trickery they tried to use. My meager opinion on it is Nintendo was too interested in the graphics chips and sound chips in development, and in the design room at the time, 88-89,the hardware guys and Nintendo programmers just didn't realize that games were going to be as in depth as they were getting upon the Snes release.

 Snes release titles are a prime example of this mentality, Super Mario World, F-Zero, and Pilot wings, all nice looking, but basic in premise, with Mario having the most going on on-screen. Once the complex games hit, like Super R-Type, Final Fight, Super Ghouls and Ghost, Gradius 3, Contra 3, ect.. it became painfully obvious that the Snes CPU was having a hard time coping with on screen action that really required faster cpu work in order to eliminate slow down. They prob felt worse comes to worse, they could offload alot of the work onto the graphics chip. Turns out if that was the case, it was a poor decision. The Snes still did really amazing things though when people learned to optimize its cpu, graphics and sound ability.

Tom

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Re: TG 16-bit processing...
« Reply #7 on: December 03, 2008, 01:12:40 PM »

 Not just overall of the SNES, but in every category including 16bit operations for direct speed of execution in comparison for PCE CPU. Some instructions can run at 3.57mhz for the SNES, but most run at maximum of 3mhz because the snes WORK RAM has wait states that slow it down. PCE runs between 1.6-1.8 MIPS. This was tested for a number of games running in a PCE emulator.

Quote
Can anyone substantiate this as I'm hardpressed to believe a single 8-bit core could have done all that

Thank god the PCE doesn't have dual CPUs at half the frequency. Dual CPUs don't translate into double the power, with most of the time the second processor not even hitting 30-50% resource mark let alone the first one.

 PCE and the 68000. The 68000 has slow memory access times (4 cycles VS HuC6280 1 cycle), but can grab a single 16bit value in one memory access. Most operations are done register to register because of this. Some instructions are pretty slow in comparison though, but the instruction set in general is pretty powerful in operation. What that means is that it's harder to write slow code on the 68000, or I should say that it's easier to write efficient code without fine tuning optimizations. The linear address of the 68k makes coding much easier too. The Huc6280(PCE) on the other hand requires specific optimizations - which are beyond the scope of this post.

 The PCE's graphic chip is 16bit(VDC) - all the way through. Everything is handled in WORDS(16bit) - WORD address define, WORD memory fetchs, read/writes, registers, data port. The other graphic chip is also 16bit, but it doesn't handle much  - mostly palette and TV/monitor signal generation. Both of the 16bit graphic chips are able to work with a 16bit CPU like the 68k or directly with an 8bit CPU like the HuC6280. Funny thing is, the Genesis graphic processor (VDP) is 8bit. 8bit bus, 8bit vram, 8bit address define, read/writes, data port(s), etc. 'Bitness' doesn't really mean much and it doesn't have a direct relation to the colors onscreen, etc. And the Genesis VDP is pretty amazing when it comes to sprites and other effects.

nat

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Re: TG 16-bit processing...
« Reply #8 on: December 03, 2008, 02:16:46 PM »
Tom? Is that you, mal? If so, welcome back, your technical contributions were missed.

Tatsujin

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Re: TG 16-bit processing...
« Reply #9 on: December 03, 2008, 02:20:30 PM »
mal is/was gone? and if yes, wth? :shock:
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Tom

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Re: TG 16-bit processing...
« Reply #10 on: December 03, 2008, 04:11:04 PM »
Tom? Is that you, mal? If so, welcome back, your technical contributions were missed.

 Am I that easy to spot? :(

termis

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Re: TG 16-bit processing...
« Reply #11 on: December 03, 2008, 05:53:49 PM »
Tom? Is that you, mal? If so, welcome back, your technical contributions were missed.

I second that.

Gentlegamer

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Re: TG 16-bit processing...
« Reply #12 on: December 04, 2008, 02:13:20 AM »
My meager opinion on it is Nintendo was too interested in the graphics chips and sound chips in development, and in the design room at the time, 88-89,the hardware guys and Nintendo programmers just didn't realize that games were going to be as in depth as they were getting upon the Snes release.
The SNES CPU was chosen because it is backwards compatible with programs written for the NES CPU. At some point in the development, NES backwards compatibility for the SNES was abandoned, but the slower CPU was retained, unfortunately.

awack

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Re: TG 16-bit processing...
« Reply #13 on: December 04, 2008, 02:16:33 AM »
Quote
Am I that easy to spot? Sad

Ha,yea, by the third paragraph i knew who it was aslo, it should definitely be taken as a complement.

Joe Redifer

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Re: TG 16-bit processing...
« Reply #14 on: December 04, 2008, 04:06:03 AM »
Quote from: Tom

Am I that easy to spot? :(


Yeah, but consider that a good thing.   :)