Search found 826 matches

by Eke
Wed Dec 23, 2015 9:11 am
Forum: Megadrive/Genesis
Topic: Question on SRAM
Replies: 14
Views: 3825

Re: Queston on SRAM

My question is: Does the size of the SRAM file that Fusion creates (or I suppose every emulator creates) just depend on how much you utilize the SRAM (like, if I only write 6 bytes, the file will be 6 bytes), or does the file get padded based on the size in the header? Or, does the size in the head...
by Eke
Wed Dec 16, 2015 1:17 pm
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 834
Views: 324343

Re: New Documentation: An authoritative reference on the YM2612

so I'm not surprised some people like Jarek doesn't want to see their's code and research research results used by someone else for making money. I am not sure if he is aware that his code is being used commercially in Genesis Plus GX ripoffs that have a lot of exposure and likely make huge profits...
by Eke
Wed Nov 25, 2015 9:29 pm
Forum: Mega/SegaCD
Topic: Sega CD (US) BIOS Disassembly @ GitHub
Replies: 7
Views: 2728

Re: Sega CD (US) BIOS Disassembly @ GitHub

CD-DA audio data is still sent to CDC (LC8951x chip which is normally used to decode CD-ROM data) and can just as well be read in buffered raw form by sub CPU. AFAIK, that's how internal CD player and Flux VU meters work. I didn't knew about Lunar animations though.
by Eke
Mon Nov 02, 2015 11:52 am
Forum: Megadrive/Genesis
Topic: M68K Interrupt Processing
Replies: 7
Views: 2187

Re: M68K Interrupt Processing

Some quick testing suggests that no emulators get the latency quite right, though a couple (Fusion and Genesis Plus GX) are good enough for Sesame Street and Genesis Plus GX is quite close (seems to be emulating roughly 4 cycles of delay, rather than a 1 instruction latency). It should be exactly o...
by Eke
Fri Oct 30, 2015 4:48 pm
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 20
Views: 3844

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

Stef's instructions make it sound like I do need to care about when the Z80 regains the bus. Or am I misunderstanding this? I don't know, maybe it's because when you need to reset z80, /RESET must be asserted long enough while Z80 has control of the bus to be effective. I'm not sure if that's reall...
by Eke
Tue Oct 27, 2015 8:09 am
Forum: Megadrive/Genesis
Topic: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?
Replies: 20
Views: 3844

Re: Noob questions: DEFINITIVE info about Z80 BUSREQ, RESET?

1) Z80 /BUSREQ is not directly connected to 68k CPU, it is handled by a dedicated chip which handles most address decoding and will assert z80 /BUSREQ if access is done to proper 68k address range and proper 68k data line is asserted. 2) It always get the bus back, there is nothing you can do to for...
by Eke
Tue Oct 20, 2015 9:57 pm
Forum: Video Display Processor
Topic: MD VDP color levels
Replies: 10
Views: 3983

Re: MD VDP color levels

These steps seem to match voltages that were measured here: http://gendev.spritesmind.net/forum/viewtopic.php?f=22&t=519&start=82 There was also some discussion here : http://gendev.spritesmind.net/forum/viewtopic.php?f=22&t=1389 Shadow Highli Normal -------- -------- --------- (0) 0.0 0.0 (0) (1) 0...
by Eke
Mon Oct 19, 2015 9:08 pm
Forum: Hardware
Topic: Interfacing CMOS 3.3V logic
Replies: 15
Views: 3461

Re: Interfacing CMOS 3.3V logic

Thanks for taking the time putting up this very detailled answer, db-electronic. So, to summarize, using resistor series as voltage divider creates a load on the cartridge port which results in a slight increase of the current going through not only cartridge but also console board parts, thus incre...
by Eke
Fri Oct 16, 2015 10:40 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 834
Views: 324343

Re: New Documentation: An authoritative reference on the YM2612

Nemesis wrote:I was actually starting up my own "at home" decapping lab, and I've got the fuming nitric acid in the garage which can attest to it
:shock:
by Eke
Fri Oct 16, 2015 10:34 am
Forum: Hardware
Topic: Interfacing CMOS 3.3V logic
Replies: 15
Views: 3461

Re: Interfacing CMOS 3.3V logic

Series resistors in line with 3.3V flash parts (such as the Krikzz product you linked) is BAD engineering. The maximum Vin those parts can handle is 4V, after that, all excess votlage is converted to latch-up current by the input clamping diodes - and also means that your console is sourcing alot o...
by Eke
Tue Oct 13, 2015 10:51 am
Forum: Video Display Processor
Topic: VDP Debug Register - $C0001C
Replies: 17
Views: 7078

Re: VDP Debug Register - $C0001C

Sprite data on the right. I still don't think this is the sprite fetch, because that should be happening much faster than this to be efficient (simply not enough hblank time to grab 320px worth of sprite data) It was actually confirmed that all the sprite pattern fetching is done during HBLANK (whi...
by Eke
Wed Oct 07, 2015 11:21 am
Forum: Hardware
Topic: Question about B31 (aka #TIME) cart pin
Replies: 14
Views: 2708

Re: Question about B31 (aka #TIME) cart pin

Couldn't you use that as A0, though? Use what ? IIRC this is how Z80 RAM gets mapped (at the expense of requiring all accesses to be 8-bit). AFAIK, Z80 A0 is asserted by the bus arbiter based on the /LDS and /UDS signals from 68k. These signals are not available on the cartridge port, only /LWR and...
by Eke
Tue Oct 06, 2015 6:51 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 834
Views: 324343

Re: New Documentation: An authoritative reference on the YM2612

From what I remember, Hellfire sometimes reads the FM status (timers and busy flags) from $4001-$4003 instead of just $4000 as recommended so maybe some (or all) of those flags can only be read correctly when A0 is low ?
by Eke
Tue Oct 06, 2015 6:42 am
Forum: Hardware
Topic: Question about B31 (aka #TIME) cart pin
Replies: 14
Views: 2708

Re: Question about B31 (aka #TIME) cart pin

Also, it's only 128 bytes if you only use /LWR and D0-D7. Only A1-A7 can be used, not A8 since /TIME is not asserted for $A131xx.
by Eke
Mon Sep 21, 2015 10:51 am
Forum: Sound
Topic: New Documentation: An authoritative reference on the YM2612
Replies: 834
Views: 324343

Re: New Documentation: An authoritative reference on the YM2612

Do you think it's possible to figure what happen with the 14-bit operator output, where algorithm connections are made to produce the final channel output, then the conversion to 9-bit DAC input ? I am still wondering if the YM2612 "ladder effect" could take place during the 14-bit -> 9-bit convers...