Search found 49 matches

by Gunstick
Sun Oct 27, 2019 11:01 pm
Forum: HARDWARE DISCUSSIONS
Topic: Put 2 YM2149 into the ST
Replies: 38
Views: 18425

Re: Put 2 YM2149 into the ST

I tried to put the 2nd YM into the same space as the current YM (so on ff8800 and ff8802), but have some additional logic to emulate new registers. So you effectively obtain a "new" YM chip with 32 registers. To address the second YM, I tap on bit 4 of the register address (which is usuall...
by Gunstick
Sat Oct 26, 2019 8:41 pm
Forum: HARDWARE DISCUSSIONS
Topic: Put 2 YM2149 into the ST
Replies: 38
Views: 18425

Re: Put 2 YM2149 into the ST

Hi

I'm no circuit designer, so no idea if this would work or if it would glitch the latching of register numbers into both YMs.

I put it into this online simulator https://circuitverse.org/users/11547/projects/33301
Screenshot_2019-10-26_21-39-58.png
Screenshot_2019-10-26_21-39-58.png (34.91 KiB) Viewed 5037 times
by Gunstick
Thu Oct 24, 2019 1:41 pm
Forum: HARDWARE DISCUSSIONS
Topic: Put 2 YM2149 into the ST
Replies: 38
Views: 18425

Re: Put 2 YM2149 into the ST

I tried to figure out how the YM is interfaced to the ST bus. Checked the original Atari documents and some of the STremake posts. But I could not figure out where BC1 and BDIR are connected to, and how they are used when accessing the YM.
by Gunstick
Mon Oct 14, 2019 9:19 pm
Forum: RAM UPGRADES
Topic: Upgrade from 1MB to 3MB instead of 2.5MB
Replies: 1
Views: 2516

Upgrade from 1MB to 3MB instead of 2.5MB

Hi in 1990 the german magazine STcomputer published in it's March issue a little addon circuit which would reenable the unused 512kB from an 1MB machine which had an added 2MB RAM expansion. That article is not yet in the online archive. The 2MB expansion has to be bank0 The circuit does the followi...
by Gunstick
Mon Oct 14, 2019 12:52 am
Forum: ALPHA DEVELOPMENT INFO
Topic: STFM Keyboard Remake
Replies: 79
Views: 39783

Re: STFM Keyboard Remake

Just a small interjection from me for new keyboard and new case projects: If the joystick ports on the underside of the keyboard PCB would be turned to face the right side of the case and be accessible from the outside, that would be way nicer than having to fiddle below the machine to change plugs....
by Gunstick
Thu Oct 10, 2019 11:50 pm
Forum: ST
Topic: C070243 Rev C (520ST+, 1MB, quite botched with extensions)
Replies: 4
Views: 7779

Re: C070243 Rev C (520ST+, 1MB, quite botched with extensions)

The ram expansion for 2.5MB to 3MB was probably published in STcomputer 03/1990 but is not referenced in the archive http://www.stcarchiv.de/stc1990.php But they have an errata in STcomputer 04/1990 with part of a diagram http://www.stcarchiv.de/stc1990/04/news will post again when I go dig through ...
by Gunstick
Thu Oct 10, 2019 11:41 pm
Forum: ST
Topic: C070243 Rev C (520ST+, 1MB, quite botched with extensions)
Replies: 4
Views: 7779

Re: C070243 Rev C (520ST+, 1MB, quite botched with extensions)

The overscan expansion is called hyperscreen and costs 2€
The description was in STmagazin 05/1985 (in german)
http://www.stcarchiv.de/stm1989/05/hyper-screen
the pictures seems to have been lost. I need to look through my own STmagazine collection and will post infos if I find them.
by Gunstick
Sun Oct 06, 2019 5:24 pm
Forum: HARDWARE DISCUSSIONS
Topic: Put 2 YM2149 into the ST
Replies: 38
Views: 18425

Re: Put 2 YM2149 into the ST

Ah, that's interesting. Also on falcon who does bus errors outside of the official YM addresses? As, for some unknown reason, there was never a dual YM done, it would be good to define how it should be connected so that software always knows where to find the chip. Best if can be piggybacked on top ...
by Gunstick
Sun Oct 06, 2019 12:42 am
Forum: HARDWARE DISCUSSIONS
Topic: Put 2 YM2149 into the ST
Replies: 38
Views: 18425

Put 2 YM2149 into the ST

Hi I was wondering if it's possible to double the YM soundchip. Not knowing exactly how the adress decoding is done by Atari, either one could simulate new YM registers from $10 to $1F, or create a second YM in the address space (but then you get battles with the MMU, especially in recent machines w...
by Gunstick
Thu Sep 19, 2019 11:24 pm
Forum: ST
Topic: C070243 Rev C (520ST+, 1MB, quite botched with extensions)
Replies: 4
Views: 7779

Re: C070243 Rev C (520ST+, 1MB, quite botched with extensions)

Gunstick520STplus-3MBcircuit.jpg I found some paper scribblings when I built the 2.5MB to 3MB converter. It has the following chips: 7400 quad 2-input NAND gate 74375 quad bistable latch 74139 dual 2 to 4-line decoder/demultiplexer, inverting outputs As input it uses CAS-L & CAS-H , RAS, A9 I s...

Go to advanced search