The truth about V9948

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Par sd_snatcher

Prophet (3498)

Portrait de sd_snatcher

06-12-2011, 01:08

@Sander
How much VRAM does this Captain have? The picture shows much more chips than the usual 4.

Par RetroTechie

Paragon (1563)

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06-12-2011, 01:25

I hope someone can some day cough up a datasheet of the V99C37... just to satisfy my curiosity.
Google has almost nothing, and this machine it's found in is quite rare AFAIK. Read: this V99C37 can't contain much circuitry otherwise it would have been too expensive to develop the chip, given the numbers produced.

So although it has many pins, it's likely there's not much logic inside. If someone would take the time & trace how all pins are connected, that would probably tell you a lot. A bit of poking around in that machine's ROMs would fill in the remaining blanks.

Not that I care Tongue you can't use the original chip since you can't buy it anywhere (and probably offers too little in comparison with the effort required to use it). If you'd want to add what it does to say, the 1chipMSX, you wouldn't need to know how this chip works but could just cook up your own scheme. Either way there's not much point in investigating what exactly it does...

Perhaps emulator ppl would like to know in order to add this machine to the list of emulated models. Question But that's about it I think.

Par sd_snatcher

Prophet (3498)

Portrait de sd_snatcher

06-12-2011, 01:28

@Manuel

With a multimeter, it should not be hard to at least get most of its pinout, since many pins are connected to known pins of the V9938.

The NTT Captain Multi Station service manual would also be of great help.

Par sd_snatcher

Prophet (3498)

Portrait de sd_snatcher

06-12-2011, 01:40


Google has almost nothing, and this machine it's found in is quite rare AFAIK.

Googling for the part# YM6011 returned very little useful results too.

Par RetroTechie

Paragon (1563)

Portrait de RetroTechie

06-12-2011, 01:43

V99C37 coprocessor chip has 256 colors palette of 260,000 colors for V9938.
Why the heck they didn't just integrated that chip on the V9958 instead of creating the complicated YJK modes?

maybe because of chip die space?
or do you think that a chip could be made larger than a surf table if needed?
What about heat ?

For a 256 color palette, you'd need 3x 256 registers for R, G, B, respectively. Assuming you'd use 8 bits for each register (=24 bit color = true color), that would be a 768 byte block of RAM, and a few bit more accurate DAC's than in V9958.

768 bytes RAM is smallish compared to all the silicon real estate that goes into a videochip like the V9958. Nor would it be a big burden on programmers to initialize such a palette. So I suppose it wasn't included because the 'powers that be' decided that V9958 was good enough (and btw you couldn't put >256 colors on screen with such a palette, unlike YJK modes). And if you really want it, you can add it externally using the V9938/V9958's color bus (like this V99C37 chip supposedly does).

EDIT: 260,000 colors = 18 bits (not 24) ? So that would be even simpler...

Par retrocanada76

Champion (480)

Portrait de retrocanada76

06-12-2011, 03:10

Hi Msxholder,

Can you type this routine below ? It will return the VDP ID. I have the feeling that bit 0 of VDP ID is the presence of co-processor:

10 DEFINTA-Z:FOREN=0TO30:READCO:POKE&HE000+EN,CO:NEXT
20 DATA 24,1,0,243,62,1,211,153,62,143,211,153,26,219,153,203,47,230,31,50,2,224,175,211,153,62,143,211,153,251,201:DEFUSR=&HE000
30 G=USR(0)
40 F=PEEK(&HE002)
50 PRINT F

It should return 0 for MSX2 and 2 for MSX2+/TR. I'm curious to see if it will return 1 on NTTs

Thank you

Par MSXPro

Resident (48)

Portrait de MSXPro

06-12-2011, 04:38

This picture seems a "true" a fake, the "4" looks photo-shopped - both thickness and orientation of the signs are at least suspicious

I'm sorry to inform you that this picture was not photo-shopped, but MS-PAINTED! Smile Yes, I have edited this file in a few minutes from this on wikipedia.

This image was edited by me to illustrate this post made by Adriano Trancoso on his blog.

Read all here:

Part 1: http://msxresources.wordpress.com/2011/11/18/v9948-o-elo-perdido-do-msx-parte-1/
Part 2: http://msxresources.wordpress.com/2011/11/19/v9948-o-elo-perdido-do-msx-parte-2/
Part 3: http://msxresources.wordpress.com/2011/11/21/v9948-o-elo-perdido-do-msx-parte-3/

The image illustrating the third post put here.

For who likes puzzles, has a little easter-egg that I left.

As explained in the blog, the V9948 so far proven otherwise, is a hoax created in 1999. :)

As they say here, a lie told 1000 times becomes truth. Apparently that's what happened in these 12 years have passed and no one questioned the right person on the veracity of the facts.

I can only laugh at this! LOL!LOL!LOL!

Par PingPong

Prophet (3839)

Portrait de PingPong

06-12-2011, 18:35

V99C37 coprocessor chip has 256 colors palette of 260,000 colors for V9938.
Why the heck they didn't just integrated that chip on the V9958 instead of creating the complicated YJK modes?

maybe because of chip die space?
or do you think that a chip could be made larger than a surf table if needed?
What about heat ?

For a 256 color palette, you'd need 3x 256 registers for R, G, B, respectively. Assuming you'd use 8 bits for each register (=24 bit color = true color), that would be a 768 byte block of RAM, and a few bit more accurate DAC's than in V9958.

768 bytes RAM is smallish compared to all the silicon real estate that goes into a videochip like the V9958.
the fact that in v9958 some v9938 funcions were removed, make me think that they were already full...
and consider plz that we were on 1985

Par msxegor

Master (183)

Portrait de msxegor

07-12-2011, 11:54


the fact that in v9958 some v9938 funcions were removed, make me think that they were already full...
and consider plz that we were on 1985

The only functions removed in V9958 are mouse and lightpen support - which were never used on MSX
(well lightpen port is present on Daewoo CPC-400/400S but i never saw a Daewoo lightpen and neither soft that used it)
I guess they were removed just to save pins for wait etc.

Its a shame that there is no V99C37 information available

PS. Both V9938 and V9958 can work with external palette, there was an enhanced board for TI system 99:
http://home.arcor.de/system-ninety-nine-user-group/evpc

I myself connected VGA RAMDAC to V9938 and it worked.

Par PingPong

Prophet (3839)

Portrait de PingPong

07-12-2011, 13:33


Quote:
I guess they were removed just to save pins for wait etc.


why not multiplexing then ?

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