Posted By
Boray
on 2005-03-29
12:25:53
|  A couple of Plus/4 questions
Hi again...
Which is the fastest, a NTSC or PAL machine?
How do you use your own charterset through basic on the c16/plus4? Pokes and addresses etc..?
I have read that the Plus/4 has two different processor speeds (.98 and 1.7MHz or something similar). Does it normally run at the slow or fast speed? Is there something like the FAST and SLOW command on the C128, or how do you change between the two speeds? Can you run at the fast speed in basic?
/Anders
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Posted By
Csabo
on 2005-03-29
15:14:18
| Re: A couple of Plus/4 questions
Finally, some cool questions. Here it goes:
1) PAL is faster. On NTSC machines, the screen is refreshed more, so there's less time for the CPU.
2) $FF12 bit 4 needs to be cleared, $FF13 points to the high byte of charset address. Example: you have your set on $3800 (very common for C16 games):
POKE 65298, 192 : POKE 65299, DEC("38")
switch back to normal:
POKE 65298, 196 : POKE 65299, DEC("D0") : REM the original set is on $D000
3) The processor is running at normal ("slow") speed by default. If you turn the screen off ( >FF06 0 or POKE 65286,0 ), it's running in "fast" mode, which is good for calculations, but of course you can't see anything.
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Posted By
Gaia
on 2005-03-29
17:03:02
| Re: A couple of Plus/4 questions
Csabo: I have to at least partially contradict you at point 1. The answer is unfortunately not that simple 
NTSC is in fact _not_ slower than PAL, actually the opposite is true. PAL has a chrystal oscillator of 17734475 Hz while NTSC has one of 14318180 Hz. The PAL clock is divided with 10, that gives us ~1,77 Mhz and the NTSC by 8 which results in ~1,79 Mhz. So the sound oscillators and timers are running "quicker" on an NTSC machine (by the half of the appropriate freqencies on each machine).
If you blank the screen by writing 11 to TED register #6 with POKE65286,11 you get 1,70 MHz on a PAL machine and 1,71 MHz on NTSC
It is true however that most of the case (when the screen is not blanked) you have fewer CPU cycles in total, because on NTSC the screen is refreshed 60 times a second as opposed to ~50 on PAL. If you take the cycles into account that are "stolen" from the CPU because of those "dreaded" bad lines and TED graphic fetch cycles, PAL is indeed faster than NTSC: approx. 1,2 MHz against 1,1 MHz.
Well, because the clocking is partly dependant on the code executed it is a little bit trickier... how about tricks such as limiting the window area or putting a PAL machine into "NTSC mode" 
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Posted By
Gaia
on 2005-03-30
02:35:45
| Re: A couple of Plus/4 questions
One more thing. TED register #19 is having a forced slow clock flag (bit #1), so if you set it to 1 by eg. POKE 65299,211 the whole machine would slow down because the processor won't get to twiee clock mode on the border area and at the end of the lines. The forced slow clock mode is turned off by default, so that means the machine is in this respect in fast mode after powerup Sorry I haven't calculates the approximate frequencies this time
Some disk turbos and demos use this bit for easier timing (and some other intros for timer based protectors... ).
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Posted By
SVS
on 2005-03-30
03:32:03
 | Re: A couple of Plus/4 questions
Pals, do you realize how much precious this info is?
Please think to a way to share all this data, maybe the long dreamed "Plus4 Acknowledge base" .
But, while waiting, simple txt files could "save" them (Please!! )
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Posted By
MIK
on 2005-03-30
03:47:13
 | Re: A couple of Plus/4 questions
Way to technical for my grey matter but since the days of Megadrive (The games console scene) and beyond I've always know NTSC was faster than Pal. Some 17.5% faster I think because NTSC displays less lines on the screen. Anything that uses maths to display GFX to the screen will be smoother such as Virtua Racing for the MegaDrive which had an independent maths processor builtin to the cart called the SVP. Come the mid 90's to the present day all games consoles displayed 3D GFX so these machines are relying on pure hardcore maths..... Having a 60Hz machine will allow for faster lap time with racing games ect over 50hz. Over a number of laps where the game is running a tad faster that saved time soon adds up.
Of course back in the 80's NTSC had no meaning to most of us european gamers. Mercenary should run faster on an NTSC Plus/4 I would of thought...
Its very rare but some times they optimize PAL games... Pal Halo for xbox runs smoother in 50hz than it does in 60hz lol.
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Posted By
Boray
on 2005-03-30
07:55:11
| Re: A couple of Plus/4 questions
Thank you very much everyone! Very helpful, but quite a bit to take in there
A bit confusing about the speeds there. You are welcome to help me with a test in practise. Download this program: http://user.tninet.se/~pug510w/qb17.zip and give me the numbers for a PAL and a NTSC machine. The program compares your speed against a bunch of other Commodore machines. I now adjusted it to run on the Plus/4 as well.
/Anders
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Posted By
Gaia
on 2005-03-30
08:06:06
| Re: A couple of Plus/4 questions
You're welcome.
I have downloaded your benchmark program. I have to add, that measuring the BASIC performance may tell little about the actual real speed of the hardware, it's more of a measure how well the interpreter is performing for example The BASIC interpreter (v3.5) of the 264 family has more features than that of the VIC-20, so I can imagine that for being a reason why I got lower benchmark results all the way.
SVS: which piece of info you mean on "precious"? I guess all this has been available already at various places (circuit diagrams, mail list archives, TED docs) although I agree that a central document (รก la VIC-Article) would be desired.
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Posted By
Boray
on 2005-03-30
11:16:55
| Re: A couple of Plus/4 questions
Yes, I know it just measures the basic. Could you please write down the numbers you got on the last screen? And tell me if you use PAL or NTSC?
If you set a NTSC machine to PAL mode (by changing $ff07 bit 6), does it then run just as a PAL machine and as fast as a PAL machine?
The machine I'm waitning on is NTSC, but I can display both PAL and NTSC on my TV... (and I am living in PAL land).
/Anders
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Posted By
Boray
on 2005-03-30
15:06:43
| Re: A couple of Plus/4 questions
Another question...
How do you do a "runstop-restore"???
I am only using VICE for now, but I can't seem to find a restore key? Isn't there any, and how do you then do something similar?
/Anders
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Posted By
Ulysses777
on 2005-03-30
19:05:16
| Re: A couple of Plus/4 questions
Hi
There is no Restore key on the Plus/4, there is a reset button instead (Alt+R on VICE, and on the right side of the actual unit). Pressing Run/stop + Reset brings up the built-in assembler, TEDMON (also accessible by the MONITOR command in BASIC) and preserves any BASIC programs in memory. Pressing Reset alone brings up the startup screen (and loses any BASIC programs).
As for your PAL/NTSC question, PAL and NTSC units have different oscillator crystals and Kernal ROMs, you can't simply run an NTSC unit in PAL mode just by changing bit 6 of $FF07 (which is only used so that the same TED chip can be used in either unit (unlike the Vic20 and C64)). Also, changing bit 6 of $FF07 screws up TI and TI$, rendering BASIC benchmarks useless.
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Posted By
Boray
on 2005-03-31
05:14:55
| Re: A couple of Plus/4 questions
Thanks, okay, so to do the equivalence of a runstop-restore, you do runstop+reset and then followed by X...? Why couln't they have kept the restore key?
/Anders
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Posted By
JamesC
on 2005-03-31
08:11:59
| Re: A couple of Plus/4 questions
The RESTORE key on other Commodore machines generates an NMI interrupt in hardware. The Plus/4 and C16 do not support NMI interrupts. Therefore, a RESTORE key would be useless.
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Posted By
Boray
on 2005-03-31
14:29:24
| Re: A couple of Plus/4 questions
Even so, they could have had a similar key to restore the TED chip to the default settings (with just system software).
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Posted By
JamesC
on 2005-03-31
16:53:48
| Re: A couple of Plus/4 questions
Maybe you don't understand (or know) the history of the TED series.
Commodore's intent was to do something different with the TED line. The Plus/4 was intended to be a business machine, the C16 a learning machine. Neither was meant to be a gaming machine like the C64.
Hence, Commodore engineering thought that a reset button was more logical to the intended users. The ability to hold down the Run/Stop key to enter the MONITOR is actually an improvement over the PET/CBM series that required a SYS to a BRK instruction, and sometimes reuined BASIC pointers when exiting.
In my opinion, the TED series were the first Commodore machines actually designed correctly. The RESTORE key had been a problem for Commodore, as people didn't understand that it had to be hit quickly and firmly, not softly like the spacebar..... and by calling it RESET it obviously returns the system to default settings.
The Commodore 128, mostly designed by the same people who worked on the TED series, kept the reset button because they saw its' value. The 128 only has a RESTORE key for 64 compatibility.
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Posted By
Boray
on 2005-04-01
04:49:59
| Re: A couple of Plus/4 questions
...But the restore key works in 128-mode too.... Even in the 80 column mode.
The restore key is useful in any application. Especially while programming.
/Anders
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