Commodore 8296GD

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Re: Commodore 8296GD

Anders Carlsson
Hello,

Rhialto wrote:
> The first post mentioned that it was piggybacked onto the character
> generator ROM and the CRTC... and so the one on the board is a *second*
> CRTC?

Steve Gray wrote:
> No, the original CRTC chip and CHARROM are transplanted to this board.
> [..] However, there IS a DIFFERENT graphics card for PET that contains
> it's own CRTC chip.

Unless I'm completely confused, the board Michal found in his 8296D was
piggybacked onto the ROM and CRTC, so if both boards are of the HR(G)E
variety, perhaps there were different ways to implement it?

Best regards

Anders Carlsson


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Re: Commodore 8296GD

Mike Naberezny
In reply to this post by Steve Gray
Hi Steve,

On 10/1/12 12:06 PM, Steve Gray wrote:
> I will try to post a D82 for you tonight, but no promises :)
> Thanks! I'll see if Mike can help with the reverse engineering or perhaps
> building a wirewrap version.

I'd like to have one of these for my 8296.  If you and Mike Stein are able to
make the schematic, I'll try building one with point-to-point soldering.  That
will verify the schematic and then we can consider a PCB.

Regards,
Mike

--
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Re: Commodore 8296GD

Steve Gray
In reply to this post by Anders Carlsson
Are we talking piggybacked board or chips? For this board you remove the crtc and chrrom chips from the 8296, install the board, then put the chips on this board. One crtc chip.

 When you say piggybacked i think of leaving the existing chip and placing another chip directly on top.. Hence two chips.

The other board has no relation to this board, its just an example of a graphics board that adds another crtc to the existing one.

Steve


On Oct 1, 2012, at 7:13 PM, "Anders Carlsson" <[hidden email]> wrote:

> Hello,
>
> Rhialto wrote:
>> The first post mentioned that it was piggybacked onto the character generator ROM and the CRTC... and so the one on the board is a *second* CRTC?
>
> Steve Gray wrote:
>> No, the original CRTC chip and CHARROM are transplanted to this board. [..] However, there IS a DIFFERENT graphics card for PET that contains it's own CRTC chip.
>
> Unless I'm completely confused, the board Michal found in his 8296D was piggybacked onto the ROM and CRTC, so if both boards are of the HR(G)E variety, perhaps there were different ways to implement it?
>
> Best regards
>
> Anders Carlsson
>
>
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Re: Commodore 8296GD

Michał Pleban
In reply to this post by Steve Gray
Yes, that's the one :-)

Steve Gray wrote:

> I posted a picture of the board here:
> http://www.6502.org/users/sjgray/temp/HRGE_Front.jpg
>  
> It looks like it would be pretty easy to figure out...
> Steve
>
>     *From:* Michał Pleban <[hidden email]>
>     *To:* [hidden email]
>     *Sent:* Monday, October 1, 2012 11:44:03 AM
>     *Subject:* Re: Commodore 8296GD
>
>     Hello!
>
>     Steve Gray wrote:
>
>     > I can re-post a 8250 format disk for you. It just happened that I
>     had an
>     > MSD drive available when I typed them.
>
>     Please do.
>
>     > would love to reverse engineer that board. If you don't mind
>     lending it
>     > to me for a couple months... you can see I don't work too fast ;-)
>
>     Sure, no problem, I am slow nowadays myself with all the company stuff
>     on my head... How's your P500 by the way? ;-)
>
>     Regards,
>     Michau.
>
>
>
>           Message was sent through the cbm-hackers mailing list
>
>


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Re: Commodore 8296GD

André Fachat
In reply to this post by Steve Gray
Cool, these pictures are awesome!
Should indeed be easy to rebuild.

My assumption is that u4 (ls244) is used to bypass the charrom, as it connects the address and data lines of the charrom.

What type of IC is u1? That is not readable... where do the lines on the flat ribbon cable go?

Great stuff, I'm going to build me one....

André



Steve Gray <[hidden email]> schrieb:
I posted a picture of the board here:
 
It looks like it would be pretty easy to figure out...
Steve

From: Michał Pleban <[hidden email]>
To: [hidden email]
Sent: Monday, October 1, 2012 11:4 4:03 AM
Subject: Re: Commodore 8296GD

Hello!

Steve Gray wrote:

> I can re-post a 8250 format disk for you. It just happened that I had an
> MSD drive available when I typed them.

Please do.

> would love to reverse engineer that board. If you don't mind lending it
> to me for a couple months... you can see I don't work too fast ;-)

Sure, no problem, I am slow nowadays myself with all the company stuff
on my head... How's your P500 by the way? ;-)

Regards,
Michau.



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Re: Commodore 8296GD

André Fachat
In reply to this post by Steve Gray
Btw, looking at the small number of chips and the ls257, that reminds me how I built hires into my selfbuilt pet replica - I used an ls257 to map the two lowest charrom address lines (char row select from the crtc) on top of the crtc memory address lines and a "pass through" character set... resulted in a weird memory layout though.

That brings me to the question - what is the memory layout of the hires mode? That should give us some more hints...

André



Steve Gray <[hidden email]> schrieb:
I posted a picture of the board here:
 
It looks like it would be pretty easy to figure out...
Steve

From: Michał Pleban <[hidden email]>
To: [hidden email]
Sent: Monday, October 1, 2012 11:4 4:03 AM
Subject: Re: Commodore 8296GD

Hello!

Steve Gray wrote:

> I can re-post a 8250 format disk for you. It just happened that I had an
> MSD drive available when I typed them.

Please do.

> would love to reverse engineer that board. If you don't mind lending it
> to me for a couple months... you can see I don't work too fast ;-)

Sure, no problem, I am slow nowadays myself with all the company stuff
on my head... How's your P500 by the way? ;-)

Regards,
Michau.



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Re: Commodore 8296GD

Michał Pleban
In reply to this post by MikeS
MikeS wrote:

> If Michau sends it to you I'm willing to help out any way I can; a
> worthy project indeed!

Are you guys able to burn necessary 2532 EPROMs as well?

Regards,
Michau.

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RE: Commodore 8296GD

Baltissen, GJPAA (Ruud)
Hallo Michał,


> Are you guys able to burn necessary 2532 EPROMs as well?

I can.


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Re: Commodore 8296GD

MikeS
In reply to this post by Michał Pleban
I'd probably add a couple of jumpers to select either 2532 or 2732 but no
problem burning either.

mike

----- Original Message -----
From: "Michał Pleban" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, October 02, 2012 4:41 AM
Subject: Re: Commodore 8296GD


> MikeS wrote:
>
>> If Michau sends it to you I'm willing to help out any way I can; a
>> worthy project indeed!
>
> Are you guys able to burn necessary 2532 EPROMs as well?
>
> Regards,
> Michau.
>
>       Message was sent through the cbm-hackers mailing list


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Re: Commodore 8296GD

Michał Pleban
In reply to this post by André Fachat
Hello!

A.Fachat wrote:

> My assumption is that u4 (ls244) is used to bypass the charrom, as it
> connects the address and data lines of the charrom.

Yes.

> What type of IC is u1? That is not readable...

It's a 74LS258.

> where do the lines on the flat ribbon cable go?

They go to a connector on the mainboard, please take a look:

http://www.flickr.com/photos/29843741@N05/8046562125/in/photostream/

Regards,
Michau.

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Re: Commodore 8296GD

Michał Pleban
In reply to this post by André Fachat

> That brings me to the question - what is the memory layout of the hires
> mode? That should give us some more hints...

That's exactly what I'm trying to figure out now :-)

Regards,
Michau.


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Re: Commodore 8296GD

Michał Pleban
In reply to this post by MikeS
MikeS wrote:

> I'd probably add a couple of jumpers to select either 2532 or 2732 but
> no problem burning either.

Good, so I will send you an EPROM dump as well.

Regards,
Michau.


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RE: Commodore 8296GD

Martin Hoffmann-Vetter
In reply to this post by André Fachat
Hello,

> Should indeed be easy to rebuild.

I think it, too. But we need the complete netlist. There are some unknown lines under the ics.

> What type of IC is u1? That is not readable...

On my pictures this must be a 74LS258!

That's my component list:
U1: 74LS258
U2: 74LS174
U3, U9: 74LS257
U4: 74LS244
U5: 2532 (from 8296 board)
U6: Socket to UC5 on 8296 board
U7: 74LS05
U8: 74LS155
U10: Socket to UC9 on 8296 board
U11: 6545-1
U12: Socket to JU1 to JU7 on 8296 board
U13: 74LS02

> where do the lines on the flat ribbon cable go?

That goes in the same orientation to JU1 to JU7 on the 8296 board!

Greetings Martin


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Re: Commodore 8296GD

Steve Gray
In reply to this post by Michał Pleban
Yes, no problem.
BTW, how is your 8296GD labelled? Does is actually say 8296GD on the sticker?
 
Steve

From: Michał Pleban <[hidden email]>
To: [hidden email]
Sent: Tuesday, October 2, 2012 4:41:24 AM
Subject: Re: Commodore 8296GD

MikeS wrote:

> If Michau sends it to you I'm willing to help out any way I can; a
> worthy project indeed!

Are you guys able to burn necessary 2532 EPROMs as well?

Regards,
Michau.

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Re: Commodore 8296GD

Michał Pleban
Steve Gray wrote:

> Yes, no problem.
> BTW, how is your 8296GD labelled? Does is actually say 8296GD on the
> sticker?

No, it says just 8296-D:

http://www.flickr.com/photos/29843741@N05/8046561597/in/photostream/

Regards,
Michau.


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Re: Commodore 8296GD

Michał Pleban
In reply to this post by André Fachat
Hello!

A.Fachat wrote:

> That brings me to the question - what is the memory layout of the hires
> mode? That should give us some more hints...

OK, here are first results of my ROM disassembly. So far I looked at a
routine at $883F which apparently is used to perform various graphics
tasks.

First of all, the routine banks out the ROMs with these instructions:

lda #$83
sta $E888

The address $E888 is in the CRTC register space. Apparently the board
intercepts this address with some latch on its own. This latch most
probably drives the values of jumpers JU1-JU7 (as you can see on my
photo, these jumpers are replaced with a connector that goes to the
video board).

The routine then reads a command number that is apparently stored at
$03A0, and depending on that it does different things. The number #$07
is apparently an initialization code, which stores zeroes in
$A000-$DFFF. So this is most probably where the video data resides.

Finally the procedure restores ROMs with these instructions:

lda #$0F
sta $E888

These are the only accesses to the $E888 register in the whole ROM.

I will proceed with analysis on how the actual video data is organized.

Regards,
Michau.


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Re: Commodore 8296GD

Michał Pleban
Hello!

The second portion of wisdom from the ROM disassembly :-)

The routine at $8C1A initializes the CRTC into graphics mode by
modifying some of its registers. The modifications are as follows:

* Register $01 (horizontal displayed) = #$20
* Register $02 (horizontal sync position) = original + #$02

* Register $06 (vertical displayed) = #$20
* Register $07 (vertical sync position) = original + #$04

* Register $0C (RAM address high) = #$02

As you can see, the registers are set up for a 512x256 bitmap (because
the CRTC "characters" are 16x8), sync pulse positions are shifted to
better position this bitmap on the screen, and display address is
changed. I suspect this change also turns on graphics display - I will
verify it in the afternoon because right now I don't have access to the
machine.

Regards,
Michau.



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Re: Commodore 8296GD

Michał Pleban
In reply to this post by Steve Gray
Hello!

Steve Gray wrote:

> Perhaps you can try some of the demos I typed in and confirm if they
> work or not on the HRE board!

I tried the demos from your disk. Generally they work, with some caveats:

* Image displayer is extremely slow (estimated 20 minutes to draw an
image - I gave up after 20% of the screen).
* Demo #3 expects 512x512 screen so the text "Commodore" is not visible.
* Etch a sketch hung on me when I tried the "Circle" option, needed a reset.

Regards,
Michau.


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Re: Commodore 8296GD

Steve Gray
Hi,
 
Thanks for testing! That's good to hear that the basic extensions/tokens are the same. Of course, I only had the 512 x 256 pixel version at the time when I did that. I now have a 512x512 version as well.
One of the neat things about the HSG board is the ability to re-define the screen co-ordinate system, so theoretically the software should work on either if written properly.
Ya, since there is NO access to the display ram, the image viewer is EXTREMELY slow. If you look at the code there's like 3 commands to draw each pixel. It does take about 20 minutes for the complete screen.
Sadly there is no pixel PLOT or PSET command. I didn't spend a lot of time on the Etch-a-sketch ;-)
 
I tried disassembling the ROM to see if there was a way to access the memory somehow but couldn't find anything, although I never completely understood the code (not enough time).
 
Steve
From: Michał Pleban <[hidden email]>
To: [hidden email]
Sent: Thursday, October 4, 2012 2:21:41 PM
Subject: Re: Commodore 8296GD

Hello!

Steve Gray wrote:

> Perhaps you can try some of the demos I typed in and confirm if they
> work or not on the HRE board!

I tried the demos from your disk. Generally they work, with some caveats:

* Image displayer is extremely slow (estimated 20 minutes to draw an
image - I gave up after 20% of the screen).
* Demo #3 expects 512x512 screen so the text "Commodore" is not visible.
* Etch a sketch hung on me when I tried the "Circle" option, needed a reset.

Regards,
Michau.


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Re: Commodore 8296GD

Michał Pleban
Hello!

Steve Gray wrote:

> Thanks for testing! That's good to hear that the basic extensions/tokens
> are the same. Of course, I only had the 512 x 256 pixel version at the
> time when I did that. I now have a 512x512 version as well.

Now that's strange, because demo #3 is written for 512x512 ;-)

> One of the neat things about the HSG board is the ability to re-define
> the screen co-ordinate system, so theoretically the software should work
> on either if written properly.

It will not, because you are using IPLOT in your demos which use
absolute coordinates :-P

> Ya, since there is NO access to the display ram, the image viewer is
> EXTREMELY slow. If you look at the code there's like 3 commands to draw
> each pixel. It does take about 20 minutes for the complete screen.
> Sadly there is no pixel PLOT or PSET command. I didn't spend a lot of
> time on the Etch-a-sketch ;-)

Yes, I noticed :-) For my image viewer, I used a simple "compression"
scheme where the software tries to draw as long vertical lines as
possible. So if there is a long row of pixels on a line, it is converted
to a single IPLOT command (and vice versa for black pixels). It works
very well for simple images (like the Commodore logo), it is hovewer
still an overkill for dithered photos or dot patterns (like the
Macintosh desktop picture).

> I tried disassembling the ROM to see if there was a way to access the
> memory somehow but couldn't find anything, although I never completely
> understood the code (not enough time).

There should be a way to access it (at least to read it) because there
is a command to print the screen in an IEEE printer. It must be in the
ROM somewhere :-)

Now with HRE it will be much easier, the pixel data is at $A000 so you
just need to write a small routine to access it (ROM must be banked out
and so the interrupts must be disabled).

Which brings a question - do you possibly have PNG or BMP versions of
the images you are using in your demos? I would like to display them on
the screen, do a memory dump of the bitmap and compare - this would tell
me everything about how the bitmap is organized in RAM.

Regards,
Michau.




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