Attempting to get a DragonPlus board going ...

A place to discuss everything Dragon related that doesn't fall into the other categories.
Pernod70
Posts: 100
Joined: Sat Apr 22, 2017 10:06 pm
Location: Croydon, UK

Re: Attempting to get a DragonPlus board going ...

Post by Pernod70 »

Serenarian wrote:It would have required a second Video RAM bank (like on the IBM MGA board) to hold the corresponding character attributes.
Good point! It definitely contains data of some kind in maybe 8 or 16 blocks, it's a mystery.

Moving onto the video timing, you say that there are (112+1)*8=904 pixels per scanline (640 displayed) and (25+1)*11=286 scanlines (24*11=264 displayed), is this correct or does CRTC R5 come into the equation?
Serenarian
Posts: 22
Joined: Thu Oct 25, 2012 1:28 pm

Re: Attempting to get a DragonPlus board going ...

Post by Serenarian »

Your figure for the number of pixels per scanline is correct 904 of which 640 are displayed.

The second question about R5, is Yes. The value in R5 is required to bring the total up to the PAL video standard of 312 scanlines per field. 312-286=26 or 25 if it is a zero based count ($1A or $19) but somehow Compusense put $1E in there which is 31. Still it works. 286+31 = 317.
Pernod70
Posts: 100
Joined: Sat Apr 22, 2017 10:06 pm
Location: Croydon, UK

Re: Attempting to get a DragonPlus board going ...

Post by Pernod70 »

Serenarian wrote:Your figure for the number of pixels per scanline is correct 904 of which 640 are displayed.
Your R0 details are incorrect:
The DragonPlus uses 112 (&h72).
I've run FLEX in MAME and it's actually set to &71 so should read: The DragonPlus uses 113 (&h71).
This brings the horizontal pixels to 912 and a scanline count of 286+30=316.
tjewell
Posts: 314
Joined: Mon Oct 19, 2009 4:58 pm
Location: Cambridge, England

Re: Attempting to get a DragonPlus board going ...

Post by tjewell »

@Serenarian - thanks, that's a really useful document! And good to know I'm not the only DragonPlus user out there.

You said "I too had a Dragon 32 that I upgraded to 64k and I patched OS9 to run on it" - do you remember what you did? Mike (@bluearcus) has very generously been trying to hack a version of OS/9 that works for my upgraded machine, but we're still seeing it hang. If you can't, is there any possibility you could post me a copy of the disk? - I can make a VDK and share with Mike (I would happily come collect, but Wales is a little way from Cambridge!).

Attached is a clipping from Dragon User, February 1986 - I'd love to know more about their plans for a hard disk interface. The later manual makes a reference about being able to upgrade the DragonPlus board to add a hard disk. They were even offering it for sale ("call for details") in their advert in the same issue of Dragon User.
compusense.jpg
compusense.jpg (17.88 KiB) Viewed 4074 times
Serenarian
Posts: 22
Joined: Thu Oct 25, 2012 1:28 pm

Re: Attempting to get a DragonPlus board going ...

Post by Serenarian »

@Pernod70...
You're quite right, the value in R0 is $71. I must be getting dozy in my old age. Actually, i KNOW I am! And my eye sight's going too.
I have the sheet of notes I made of the table and should know better - its correct at other places in the document!
I did say the document might need editing. Incidentally I hope it loads alright. I did it in an old version of word, but the pagenation is screwed up in Libre Office.
Serenarian
Posts: 22
Joined: Thu Oct 25, 2012 1:28 pm

Re: Attempting to get a DragonPlus board going ...

Post by Serenarian »

@tjewell. What did I do to get OS9 to boot on an upgraded Dragon32?

Now you're asking! It was 30+ years ago remember and although I made notes of most of the things we did to our software and hardware the Dragon was just a hobby. I was using other computers for work at the time. I will see what I can find -and I'd better check that this disk is still readable. I'll come back to you later to get an address to post a copy.
Serenarian
Posts: 22
Joined: Thu Oct 25, 2012 1:28 pm

Re: Attempting to get a DragonPlus board going ...

Post by Serenarian »

@tjewell

It turns out that was easier then I expected. I did make notes (in a school exercise book) ... and I did find them!

Here's what I wrote (exactly as it is in my notes)

"ALTERATIONS TO OS-9 TO ENABLE IT TO RUN ON AN UPGRADED DRAGON32

The PIA at FF00 -> FF03 uses a pin to check memory size on the Dragon32 which is used to switch ROMs on the Dragon64.
Try this method of altering the OS-9 disk...

10 CLEAR 5000
20 X$=CHR$(&H1A) + CHR$(&H50) +STRING$(4,&H12)
30 SREAD 1,0,3,A$,B$
40 MID$(A$,3,6)=X$
50 SWRITE 1,0,3,A$,B$
Then... is the value CHR$(&H50) correct or is it 50 decimal ?
Then... Will the CRC be correct now?"

Underneath in red pen "alterations work well - OS9 now runs on a Dragon32 - but without serial port/second terminal "
OK. I've just checked that. The value is &H50 (and not 50 base10)

So there you are. Try it on a copy of OS9 Level1 version 1.2 - assuming you have Dragon DOS to use the SREAD/SWRITE commands.

P Mooney
Serenarian
Posts: 22
Joined: Thu Oct 25, 2012 1:28 pm

Re: Attempting to get a DragonPlus board going ...

Post by Serenarian »

Re "Your R0 details are incorrect:"

I've just made the correction to my Compusense DragonPlus document to correct the mistake pointed out by Pernod70. Please use this version...

P Mooney
Attachments
COMPUSENSE DRAGON PLUS BOARD.zip
Compusense DragonPlus - Revised
(128.23 KiB) Downloaded 181 times
tjewell
Posts: 314
Joined: Mon Oct 19, 2009 4:58 pm
Location: Cambridge, England

Re: Attempting to get a DragonPlus board going ...

Post by tjewell »

@Serenarian - I can confirm that your little program works and it's patched my OS9 disk so it boots. Thanks!
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