October 17, 2019, 08:17:29 PM

Author Topic: The C64, returns.  (Read 711 times)

Offline Xerra

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Re: The C64, returns.
« Reply #15 on: July 01, 2019, 05:09:57 PM »
BTW,  the specs say that it will boot in Vic20 mode basic.  Did Vic20 have a different set of basic instructions than the C64.

I know that the screen size of the Vic20 was smaller than the 64, but did it have sprites as well, and did it have a SID chip?

Vic 20 didn't have sprites. Some people were clever enough to simulate them in software but it wasn't practical for games, even with a 16k or 32k expansion, because it took so much memory to do it. Not to mention it wasn't very quick either.

There was no Sid chip in the Vic 20. From memory it had 2 sound registers and a white noise generator.

The instruction set was the same as the Vic 20. I'm not sure it was identical and some of the illegal op-codes were probably new to the C64 but you could port games which didn't use sprites pretty easily by just taking into account the smaller screen size and changing the screen memory location variables. A game like Gridrunner or Matrix which Jeff Minter originally wrote on the Vic 20 probably only took him a couple of hours to port to the C64 and most of that would be changing the sound routines.

Offline dawlane

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Re: The C64, returns.
« Reply #16 on: July 01, 2019, 09:51:06 PM »
BTW,  the specs say that it will boot in Vic20 mode basic.  Did Vic20 have a different set of basic instructions than the C64.

I know that the screen size of the Vic20 was smaller than the 64, but did it have sprites as well, and did it have a SID chip?
The VIC-20 and C64 are two totally different machines hardware wise, with both being based on the MOS 6502 CPU. Note that the CPU  (MOS 6510 CPU) in the C64 has a different pin arrangement to cater for dynamic ram and rom banking. The VIC 20 used static ram.

The BASIC language was the same with the difference being the boot up greeting. The Video Interface Chip in the VIC-20 had no true bitmap graphics mode or hardware sprites, but did have two character modes: high resolution two colour and a four colour low resolution mode. You could fake a bitmap mode by redefining the character set in double height character mode with a memory expansion cartridge. The VIC chip also handled the sound using three pulse-wave voice generators with each voice having only a three octave range and a white noise channel. The three voices octaves overlapped in the middle ranges.

Most of the advanced games were released as cartridges, which could get round memory limitation issues.

Offline therevills

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Re: The C64, returns.
« Reply #17 on: July 02, 2019, 03:45:56 AM »
I wonder if their is any chance of an Amstrad CPC version... one can dream....

Offline Qube

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Re: The C64, returns.
« Reply #18 on: July 02, 2019, 05:22:36 AM »
I wonder if their is any chance of an Amstrad CPC version... one can dream....
Nah, to peak interest it'd have to ship with a keyboard that felt like the awesome CPC6128 as anything else would just break the feel.
Until the next time...