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Casio PV-1000


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#26 carlsson OFFLINE  

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Posted Thu Nov 30, 2017 4:41 AM

On many systems, the text based graphics system is arranged like this:

 

Screen matrix that holds an index to each character on screen, e.g. 32x24 or 22x23 (many other combinations possible depending on hardware). Each position has one index, but each index can be used many times on the screen.

 

Colour matrix that holds a combination of background and foreground colour for each character on the screen, arranged in the same way as the screen matrix. Some systems have one single background colour for the entire screen, while others will let you define both the background and foreground colour for each character. Often those are separated so the bottom 4 bits define the foreground and the upper 4 bits define the background. It would allow up to 16 different colours for each, but it isn't to say that the hardware will recognize so many combinations.

 

ROM memory which has the graphic definitions of each character, and this is what the indexes in the screen matrix refers to. By changing pointers, on some systems you can allocate an equally large part of RAM memory instead which you fill with your own character definitions for custom graphics, thus replacing the the ROM.

 

The colour clash that appears on early systems is due to the fact that each character (usually 8x8 pixels, but some systems may have 6x8, 6x9, 8x14, 8x16 etc pixels big characters) can only have one background and one foreground at a time, sometimes only one foreground in case the background is fixed for the entire screen. Thus when a moving object (software sprite) of one colour runs into another object of a different colour, the programmer will have to decide which object's colour should have precedence, while at the same time keep redefining the graphics to get the effect of a software sprite. I think this may be what is referred to as a black box above, that a software sprite rather does not try to merge with other objects if the colours are not matching, but instead is surrounded by blank (black) space.

 

A system that has hardware sprites is not affected by this, as those sprites are defined separately and can move freely on top of other graphics, using its own foreground colour.

 

From what I observed, it seems like the PV-1000 might have higher colour resolution per character than just one background and one foreground colour. Systems like the Acorn Electron, BBC Micro and I think Oric-1 are examples of such. While they mostly seem to be character based and would have cases of colour clashes, if colours can be defined e.g. per line that makes up the character, they can be prettier and in some cases make it possible to have 3-4 different colours within one 8x8 cell.

 

In high resolution bitmap modes, you might be having bitplane graphics or other ways to set the colour of each pixel but that is a very memory hungry method that is quite unusual to use in games where a lot of stuff needs to move and possibly be redefined on the go. Thus your way of thinking is relevant, but usually not applicable to how character based graphics tend to work.

 

Also Nitrofurano tends to stop by here every now and then. Perhaps he'll be around shortly in case you want to ask if he has experimented any more with Boriel's ZX BASIC compiler on the PV-1000. I have never studied it in detail to see if it has general purpose graphics commands that the compiler translates to best suitable, or if just the main engine parts of a program would be portable within different targets of the compiler and the A/V stuff will need tailoring and knowledge of the particular target. It seems to me that most Z80 based systems have unique graphics, but perhaps there is a defined baseline.



#27 pacman000 ONLINE  

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Posted Fri Dec 1, 2017 12:42 PM

https://translate.go...Sx9WAeKL1Ww-zIQ

Looks like the Casio PV-1000 shows up on Yahoo Japan Auctions fairly often. 10,000 to 38,000 Yen or:

$89.63-$340.60 USD
$113.94-$432.987 CND
$117.704-$447.27 Australian Dollars
67.23 - 255.4751 British Pounds

Not sure what it would be like trying to order something from someone in another country tho.

#28 pacman000 ONLINE  

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Posted Sat Dec 2, 2017 1:31 PM

 

Video explaining 8-bit computer graphics.



#29 carlsson OFFLINE  

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Posted Sat Dec 2, 2017 3:11 PM

Nice tutorial, I've seen it before. However he mentions 8K of memory for a 320x200 display which corresponds to a monochrome bitmapped display. Not all computers or consoles had the memory capacity for a such display, and even those who did had similar colour restrictions like he mentions in the video and which I mentioned in my post above.

 

Based on the emulation pictures of the Casio, it seems like it really used a text based display with custom character generator, which uses e.g. 32x24 = 768 bytes for the screen matrix, another 32x24 = 768 bytes for the colour matrix (with the possible disclaimer it may support more colours per cell and thus use more memory for the colour matrix), and then 256 * 8 = 4096 bytes for the character generator assuming it supports all possible 256 values - it might be restricted to 128 characters and that the hardware automatically inverts any character with an index above 127. That would be 768 + 768 + 4096 = 5632 bytes, a bit less than 9 * 1024 = 9216 bytes.



#30 carlsson OFFLINE  

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Posted Wed Apr 25, 2018 8:13 AM

Inspired by Masschamber's status update, I went back and looked at pictures of the PV-1000 and PV-2000 cartridges. Externally they have the same form factor like every other Famicom, MSX, Sord M5, (western) SMS etc game. We saw pics of a PV-1000 cartridge PCB, but I haven't managed to lookup a PV-2000 cartridge PCB. I would imagine they have the same number of pins and possibly electronically same pinout, just that the two systems have different chipsets and memory maps (the NEC Z80 clone is the common denominator). If that is a correct assumption, it meant Casio could order a larger volume of cartridge shells as well as cartridge PCBs where only the ROM chip installed would need to be different depending on the game and the system. It is an interesting thought, as the two were released almost simultaneously with on purpose different hardware.

 

However the PCB opening in the shell seems much too narrow for Casio to reuse leftover shells for later MSX games unless they went crazy with hacksaws...



#31 pacman000 ONLINE  

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Posted Wed Apr 25, 2018 10:36 AM

I wonder why that cartridge form factor was so popular...

 

It's kinda sad Casio abandoned the PV-1000 & 2000 so quickly. I wonder how this affected their users. Did Casio offer some sort of buy-back program, or were sales so abysmal that they didn't risk offending too many buyers?


Edited by pacman000, Wed Apr 25, 2018 10:36 AM.


#32 mbd30 OFFLINE  

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Posted Wed Apr 25, 2018 1:55 PM

Yeah that's a really common thing for old computers.  The Vic-20 had that issue on several games as well.


VIC-20 Qbert looks so shoddy because of that. Well, it's one reason.

#33 mbd30 OFFLINE  

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Posted Wed Apr 25, 2018 2:36 PM

It looks like a neat system that does well with single screen arcade titles. It may have been able to compete with Colecovision but not the Famicom.

#34 carlsson OFFLINE  

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Posted Wed Apr 25, 2018 4:59 PM

As Masschamber commented in his update, the PV-2000 virtually is a Colecovision, a SG-1000, a Sord M5 etc while its little brother the PV-1000 had a unique though much more limited chipset both when it comes to graphics and sound. From a nostalgic point of view, Casio probably should never have bothered with the PV-2000 or at least made it fully compatible with the PV-1000, but from a 1983 sales point of view, they probably had to try to at least catch up with the competition instead of on purpose release something inferior (hello Mattel Aquarius!).

 

Regarding the cartridge form factor, the exterior is nearly identical to the shell for a micro cassette. There may even be storage boxes for cassette tapes that will accommodate loose cartridges, unless they're 1 mm too thick. Of course the cartridges were sold in an outer packaging that often is similar but not identical size across different formats so probably not a packaging/storage reason so many went for the same size, but then again IIRC the Atari 2600, Colecovision, Intellivision etc have nearly the same size cartridge shells too, but with as many small differences as the "Japanese" ones have inbetween them, making every shell unique anyway.

 

There probably are more systems with the same sized cartridges, though I can't name which right now. The Sord M5 appears to have been launched in Japan in mid-late 1982, while the Famicom, MSX and the two Casio systems all are 1983 vintage. If there were cartridges of that form factor before the M5, I can't tell without comprehensive search but quite possibly.



#35 masschamber OFFLINE  

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Posted Thu Apr 26, 2018 4:03 PM

As Masschamber commented in his update, the PV-2000 virtually is a Colecovision, a SG-1000, a Sord M5 etc while its little brother the PV-1000 had a unique though much more limited chipset both when it comes to graphics and sound. From a nostalgic point of view, Casio probably should never have bothered with the PV-2000 or at least made it fully compatible with the PV-1000, but from a 1983 sales point of view, they probably had to try to at least catch up with the competition instead of on purpose release something inferior (hello Mattel Aquarius!).

 

Regarding the cartridge form factor, the exterior is nearly identical to the shell for a micro cassette. There may even be storage boxes for cassette tapes that will accommodate loose cartridges, unless they're 1 mm too thick. Of course the cartridges were sold in an outer packaging that often is similar but not identical size across different formats so probably not a packaging/storage reason so many went for the same size, but then again IIRC the Atari 2600, Colecovision, Intellivision etc have nearly the same size cartridge shells too, but with as many small differences as the "Japanese" ones have inbetween them, making every shell unique anyway.

 

There probably are more systems with the same sized cartridges, though I can't name which right now. The Sord M5 appears to have been launched in Japan in mid-late 1982, while the Famicom, MSX and the two Casio systems all are 1983 vintage. If there were cartridges of that form factor before the M5, I can't tell without comprehensive search but quite possibly.

the tomy tutor's carts are really similar too, and it is again another tms9918 system.  The pv 1000/2000 added another layer of stupid from casio as they actually would release msx machines a few months later.



#36 carlsson OFFLINE  

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Posted Thu Apr 26, 2018 4:07 PM

I suppose there was a lead time on everything back then just like now. The MSX standard was official in June 1983 if I recall correctly (too tired to use Google) but possibly it was worked out with all participating manufacturers before that. It could very well be so that Casio just like Nintendo and Sega were planning their own systems, and late in the process Casio decided to become a MSX manufacturer which meant either they should halt the development of the PV-1000 and PV-2000 right away while working on their first MSX computer, or go ahead and see if those would fly, depending on how much they already had invested.






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