Search found 513 matches

by sorchard
Mon Apr 11, 2022 4:25 pm
Forum: Dragon General
Topic: OLL '22 Video Games Convention
Replies: 3
Views: 1020

Re: OLL '22 Video Games Convention

sixxie wrote: Mon Apr 11, 2022 3:08 pm nice one :) which level?
Level 19. MIght have got a little bit further but had to play standing up.

I then played Doom for half an hour and gave myself motion sickness. Guess I'm starting to feel my age :)
by sorchard
Mon Apr 11, 2022 2:45 pm
Forum: Dragon General
Topic: OLL '22 Video Games Convention
Replies: 3
Views: 1020

OLL '22 Video Games Convention

We had a family afternoon out at the recent OLL '22 Video Games Convention as it was close to where we live. The Centre for Computing History had quite a large presence and I was pleasantly surprised to see a D32 set up with Chuckie Egg. Of course I felt obliged to put my name on the high score tabl...
by sorchard
Fri Jan 14, 2022 2:25 pm
Forum: Dragon Hardware
Topic: D64 with new Dragon PSU issue
Replies: 12
Views: 2611

Re: D64 with new Dragon PSU issue

Curious that it works in a D32. Can't really say much else without seeing a schematic and more detailed measurements.

Assuming you've followed the build instructions to the letter, the ball is very firmly in the court of the supplier and/or designer.
by sorchard
Fri Jan 14, 2022 9:34 am
Forum: Dragon Hardware
Topic: D64 with new Dragon PSU issue
Replies: 12
Views: 2611

Re: D64 with new Dragon PSU issue

I would use an oscilloscope to see how much ripple there is on the supplies. The fact that it works when more current is drawn suggests one of the supplies is moving to a more stable region, which in turn suggests an incorrect component value. A component value could be incorrect because it was put ...
by sorchard
Mon Jan 03, 2022 9:45 pm
Forum: Dragon Hardware
Topic: Display bars
Replies: 2
Views: 869

Re: Display bars

Hmm, strange one. In my experience, jail bars on Dragons are usually caused by missing bypass caps on the DRAM array, and fitting all eight 100n caps virtually eliminates them. I don't think I've ever seen hum bars on a Dragon. That tends to indicate a fault, particularly if you say 1u caps didn't m...
by sorchard
Thu Dec 30, 2021 12:07 pm
Forum: For Sale
Topic: Blockdown cartridges for sale
Replies: 2
Views: 1164

Re: Blockdown cartridges for sale

Love the artwork! Brilliant :)
by sorchard
Sat Dec 11, 2021 5:32 pm
Forum: Hints and Tips
Topic: Some useful short 6809 routines
Replies: 2
Views: 1913

Re: Some useful short 6809 routines

Cool. Thanks for sharing :) There is an old trick for converting a binary digit to ascii hex that is fewer bytes than the branching version: adda #$90 daa adca #$40 daa Also, I wonder how the long multiplication compares with a version that uses 6809 MUL (8x8) to generate the partial products.
by sorchard
Fri Dec 03, 2021 8:58 pm
Forum: Dragon Hardware
Topic: Dragon 64 internal DS1315 RTC board
Replies: 9
Views: 2156

Re: Dragon 64 internal DS1315 RTC board

Doesn't RTI spit a dead cycle at the end though?! It does, but the beautiful thing is that it emits the stack pointer during that cycle rather than FFFF :ugeek: Something similar happens to allow say LDA ,X to work. It runs for four cycles: First two cycles are opcode and postbyte, then there is a ...
by sorchard
Fri Dec 03, 2021 6:33 pm
Forum: Dragon Hardware
Topic: Dragon 64 internal DS1315 RTC board
Replies: 9
Views: 2156

Re: Dragon 64 internal DS1315 RTC board

Not quite sure where this lies on the filthometer, but one code trick I'm fond of is using rts with a preloaded stack as a fast loop counter or sequencer. A similar thing can be done with puls regs,pc to quickly make a series of function calls with parameters. This approach is nicer because it respe...
by sorchard
Thu Dec 02, 2021 4:40 pm
Forum: Dragon Hardware
Topic: Dragon 64 internal DS1315 RTC board
Replies: 9
Views: 2156

Re: Dragon 64 internal DS1315 RTC board

Just some proof of concept code to access the rtc without switching roms.

Should help with getting one of these working in a Dragon 32.