Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
 Welcome to our latest new user Claustro ! (Registered 2019-12-10) You are not logged in 
CSDb User Forums


Forums > C64 Coding > Ultimax unleashed..
2019-11-21 10:59
andym00

Registered: Jun 2009
Posts: 44
Ultimax unleashed..

Well, someone did what I've been wanting to do for some time.. Driving VIC fetches from external memory, and stuffing register writes over the bus.. Hooray for Ultimax mode I guess :)

Always wanted to build something like this, but kudos to Laurent for acutally getting there..

https://www.youtube.com/watch?v=yy4Gr11EXHM

He's got a few videos up of it in action.. Nothing ultra crazy, but proof it's all working..
https://www.youtube.com/channel/UCDfSVxlHK9AJHPRCoGqDYZQ
 
... 6 posts hidden. Click here to view all posts....
 
2019-12-03 16:02
knue

Registered: Dec 2012
Posts: 32
What kind of sorcery is this? Can someone enlighten me???

My understanding is that an external CPU within the CRT drives the entire machine while the 6510 is idle - correct? Why must it be Ultimax mode and what does DMA mode mean in this context?
2019-12-03 16:28
Golara

Registered: Jan 2018
Posts: 168
Quote: What kind of sorcery is this? Can someone enlighten me???

My understanding is that an external CPU within the CRT drives the entire machine while the 6510 is idle - correct? Why must it be Ultimax mode and what does DMA mode mean in this context?


Yes, 6510 is idle and he's feeding VIC with registers using external CPU. When you have a BADLINE VIC will raise some line which makes the CPU idle, that's when you can inject your own CPU... I think that's how ultimate 1541-II works but don't quote me on that :P Ultimax mode... I know it banks out all the ram, leaving you with 4kb rom image, but I don't know why it's relevant here
2019-12-03 17:12
Krill

Registered: Apr 2002
Posts: 1308
Ultimax mode is the only PLA setting which allows VIC to fetch external data, due to a lot of open memory ranges.
There will be no chip-select signal to any chips on the motherboard for those, so a cartridge can snoop on the address bus and put anything on the data bus for the open addresses, without conflicts.

This is also why you can briefly see a "charset" in RAM at $1000..$1fff or $9000..$9fff (and not the chargen ROM) when freezing with Action Replay or similar catridges, which exploit the Ultimax mode.
2019-12-03 18:47
JackAsser

Registered: Jun 2002
Posts: 1556
Quote: Yes, 6510 is idle and he's feeding VIC with registers using external CPU. When you have a BADLINE VIC will raise some line which makes the CPU idle, that's when you can inject your own CPU... I think that's how ultimate 1541-II works but don't quote me on that :P Ultimax mode... I know it banks out all the ram, leaving you with 4kb rom image, but I don't know why it's relevant here

Ultimax=allow the vic to read external ROM
DMA=put the cpu in idle state
2019-12-03 20:48
knue

Registered: Dec 2012
Posts: 32
ic, thanks :)
2019-12-04 08:05
Martin Piper

Registered: Nov 2007
Posts: 401
And the ROM doesn't have to be a ROM, it can be any signal from any source.
2019-12-04 11:48
Krill

Registered: Apr 2002
Posts: 1308
Quoting Martin Piper
And the ROM doesn't have to be a ROM, it can be any signal from any source.
Thought that as well, but technically, VIC always only reads data (except for RAM refresh). =)

Then again, the CPU may also write to external addresses (if not permanently halted by perpetual DMA).

Anyhow, with VIC reading external data, one could make something that would convert whatever video signal to VIC bitmap/characters (with FLI and sprites and whatnot) at full 50 Hz refresh rate. Kinda lame, but kinda cool as well. View random videos through a realthing VIC filter.
2019-12-04 12:50
Golara

Registered: Jan 2018
Posts: 168
Quote: Quoting Martin Piper
And the ROM doesn't have to be a ROM, it can be any signal from any source.
Thought that as well, but technically, VIC always only reads data (except for RAM refresh). =)

Then again, the CPU may also write to external addresses (if not permanently halted by perpetual DMA).

Anyhow, with VIC reading external data, one could make something that would convert whatever video signal to VIC bitmap/characters (with FLI and sprites and whatnot) at full 50 Hz refresh rate. Kinda lame, but kinda cool as well. View random videos through a realthing VIC filter.


I'd rather just take out the VIC chip and build the rest of the system around it. The dram refresh feature can be just ignored, right ?
2019-12-04 13:18
Krill

Registered: Apr 2002
Posts: 1308
Plugging in a cartridge is way easier and less likely to kill a precious C-64 or VIC itself. =)

And i think running the VIC in a non-native environment comes with a whole new set of problems, including the analogue sort.
2019-12-04 15:49
Golara

Registered: Jan 2018
Posts: 168
Quote: Plugging in a cartridge is way easier and less likely to kill a precious C-64 or VIC itself. =)

And i think running the VIC in a non-native environment comes with a whole new set of problems, including the analogue sort.


I wish the day was longer than 24 hours, there's so much stuff I'd love to try, including this. Just few weeks ago I bought myself STM32 board and even managed to generate analog 15Khz RGB video on it. I feel like I could get something like in the OP here, but I've got so many things going on, work, demos intros, games... I regret not getting into this sooner when I was still in school hehe
Previous - 1 | 2 - Next
RefreshSubscribe to this thread:

You need to be logged in to post in the forum.

Search the forum:
Search   for   in  
All times are CET.
Search CSDb
Advanced
Users Online
RedAlert
קєคςє๓คкєг/SHAPE/HiT..
Lynx/ΤRIΛD
la-style/G*P
iceout/Avatar/HF
Guests online: 39
Top Demos
1 Uncensored  (9.7)
2 Unboxed  (9.7)
3 Coma Light 13  (9.7)
4 Edge of Disgrace  (9.7)
5 Comaland 100%  (9.6)
6 Lunatico  (9.6)
7 The Shores of Reflec..  (9.5)
8 Rivalry  (9.5)
9 C=Bit 18  (9.5)
10 X Marks the Spot  (9.5)
Top onefile Demos
1 Instinct  (9.6)
2 Crystal Gazer  (9.6)
3 Dawnfall V1.1  (9.5)
4 Smile to the Sky  (9.5)
5 The Tuneful Eight [u..  (9.5)
6 Field Sort  (9.5)
7 Space Demo  (9.5)
8 The Tuneful Eight (U..  (9.5)
9 Daah, Those Acid Pil..  (9.5)
10 Innervasion  (9.5)
Top Groups
1 Oxyron  (9.4)
2 PriorArt  (9.4)
3 Fossil  (9.4)
4 Booze Design  (9.4)
5 Censor Design  (9.4)
Top Diskmag Editors
1 hedning  (9.8)
2 Jazzcat  (9.5)
3 Newscopy  (9.4)
4 Peter  (9.3)
5 Remix  (9.2)

Home - Disclaimer
Copyright © No Name 2001-2019
Page generated in: 0.044 sec.