Search found 53 matches

by flamewing
Tue Mar 21, 2017 1:17 pm
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 36
Views: 21522

Re: Undefined behavior for ABCD and SBCD

Yes. For me, who is not familiar with transistor stuff is not easy to figure out what it is: http://i.imgur.com/oXe6EJ7.png I had to google "transistor notation schema", to find something close, but closest what I've found is here: https://en.wikichip.org/wiki/cmos This picture: https://en.wikichip...
by flamewing
Tue Mar 21, 2017 11:07 am
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 36
Views: 21522

Re: Undefined behavior for ABCD and SBCD

I do not understand, hasn't anyone looked at the CPU die shots yet? Basic die shots. Then, Quietust has made a great contribution by isolating the metal traces . Olivier Galibert was able to make use of this layer image, with a few corrections, to produce a full transistor-level schematic of the 68...
by flamewing
Tue Mar 21, 2017 12:54 am
Forum: Megadrive/Genesis
Topic: Aggregating Code Snippets
Replies: 6
Views: 2555

Re: Aggregating Code Snippets

Here are some highly optimized versions of VRAM command words: ; Input: d0 = target VRAM address ; Output: d0 = VDP command longword for write to said address VRAM_Write: lsl.l #2,d0 ; Move high bits into (word-swapped) position, accidentally moving everything else addq.w #1,d0 ; Add upper access ty...
by flamewing
Mon Mar 20, 2017 9:58 pm
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 36
Views: 21522

Re: Undefined behavior for ABCD and SBCD

FYI, I reuploaded the ROM because, as it turns out, I had an earlier nonworking version layout around which got uploaded instead. My ROM have same goal, but: 1) it has source 2) it has easier bcd implementation AFAIR it has correct bcd implementation I can easily post the source for mine; but since ...
by flamewing
Mon Mar 20, 2017 2:47 pm
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 36
Views: 21522

Re: Undefined behavior for ABCD and SBCD

Even BlastEm? Yes, every emulator. Although to be fair, BlastEm does better than most and passes all abcd and nbcd tests, failing only on sbcd: http://i.imgur.com/XwrZi41.png First four rows are the number of errors per instruction; "value" is how many results were wrong, "flags" is how many flags ...
by flamewing
Sun Mar 19, 2017 4:02 pm
Forum: Megadrive/Genesis
Topic: Undefined behavior for ABCD and SBCD
Replies: 36
Views: 21522

Re: Undefined behavior for ABCD and SBCD

So, I decided to conduct my own investigation into this issue, and did some HW tests, patent investigation, and number crunching; and after doing all that, I discover this thread, in which I confirm my findings that every single emulator does it wrong. In any event, here are my findings, and I hope ...
by flamewing
Wed Oct 08, 2014 10:14 pm
Forum: Video Display Processor
Topic: Vdp Signal
Replies: 4
Views: 5304

I am no expert, but I have to confess I don't think they are entirely accurate for the pixel counts per line (numbers for the lines seem fine). Using the best numbers I can find, I come up with the following for H40 mode in NTSC: hsynch ~ 31.55 pixels back porch ~ 30.20 pixels front porch ~ 10.07 pi...
by flamewing
Tue Sep 23, 2014 6:31 pm
Forum: Exodus
Topic: Finally!
Replies: 21
Views: 12980

Out of curiosity, are these numbers for the microcode-accurate 68k core or for the old core?