Hi, Thanks a lot for this great opl implementation :).

I noticed some opl/opl2 tunes from a lot of games do not sound as the original ones.

For example the music from terra cresta:
1 - Recorded from MiSTer core): Terra cresta_JTOPL.zip
2 - Original (vgmrips.net) click on "02 theme of terracresta": https://vgmrips.net/packs/pack/terra-cresta

I noticed the drums have very low volume on jtopl.

This opl implementation has been included in the pcxt core, so I made a vgm player for 8088 cpu, and the result is the same. I found a lot of themes with low volume drums, all of them seem to use the "percussion mode" of ym3526 (terra cresta) and also ym3812.

In percussion mode, the chip can output 6 melodic instruments and 5 percussion ones (which seem to output wrong, or at very low volume in the cores).

Another example is the Wacky Wheels intro theme (ym3812):
1 - Recorded from PCXT core, sorry this also has some clicks and noises, I don't know if this is a problem of the core, or the opl: WWHeels_JTOPL.zip
2 - Original (vgmrips.net) click on "02 Dream": https://vgmrips.net/packs/pack/wacky-wheels-ibm-pc-at

Thanks!.

When using the module in external projects, it's not really convenient to use an external tool to convert the yaml to qip. And then why https://github.com/jotego/jtopl/blob/master/hdl/jtopl2.qip kept in the repo, but jt26.qip is not?
Thanks for considering adding back the qips ;)

First of all thanks for making this project and releasing it, is really great.

When playing around with the verilator vgm player, I noticed that the jtopl.f file is missing from the hdl directory.
Both gather.f and jtlopl2.f still refer to this file.

I was able to get things running again by checking out the jtopl.f file from a previous commit.

It seems like commit 8d02416 removed this file.

I assume this was by mistake as it was added explicitly in commit a38aeac.

As soon as 0xff is loaded, overflow will be 1, and at the next cycle, flag will be 1, too.
Changing the flag setting condition fixes it (if it has to be fixed)

else if( cenop && zero && load && overflow) flag<=1'b1;

Also it makes the Adlib detection code in Wolf3d work:
https://github.com/id-Software/wolf3d/blob/05167784ef009d0d0daefe8d012b027f39dc8541/WOLFSRC/ID_SD.C#L1585

I think this bug also makes the timer to fire the irq one count earlier and correcting this will have an effect to the free-running counter, as in your comment:

// Free running counter, resetting
// the value of this part with the load
// event can slow down music, vg Bad Dudes

Plus: are you sure flagen only masks the IRQ, not 'load' (e.g. doesn't stop the timer?)

Reported by e-mail. This probably refers to 2a44a7f

That commit features the single-cycle write on channels. It causes problems in cores so jtcores is using an earlier commit. This issue report might be related to that.

ERROR:Xst:880 - "jtopl_reg_ch.v" line 108: Cannot mix blocking and non
blocking assignments on signal .
ERROR:Xst:1468 - "jtopl_pg_sum.v" line 39: Unexpected event in always
block sensitivity list.
ERROR:Xst:902 - "jtopl_eg_final.v" line 41: Unexpected ksl_lut event
in always block sensitivity list.

These are minor and are easy to get around...
"jtopl_reg_ch.v"... I just remove line 108

"jtopl_pg_sum.v"... I replace the reg by a wire outside the always block
wire [21:0] phinc_mul = { 5'b0, phinc_pure} * factor[mul];

"jtopl_eg_final.v"... same, I use a wire instead of reg
wire [ 7:0] ksl_base = {1'b0, ksl_lut[fnum]}- { 1'b0, 4'd8-{1'b0,block}, 3'b0 };

I played ROL file (song file) on player in ao486. But drum sounds weird. Fix possible?

I've tried to put this OPL2 code to the Next186 SOC here:
https://github.com/gyurco/Next186/tree/jtopl

As this is much more resource-friendly than the original, it looks a great replacement. However there are some issues:

• sounds are often missing if the CPU writes too fast. That might be not a jtopl2 issue, but the game itself doesn't prepared for fast CPUs. However the original has a kind of FIFO between the CPU and the opl3 (reminds me of the Genesis core). Is it possible somehow to expose a 'busy' bit for implementing such FIFO?
• some sounds are wrong even if the CPU is slowed down. Example: Buzz Aldrin's Race Into Space. There's a 'ringing' sound where it shouldn't. I can try to export from Dosbox to VGM to check if it helps.

This song doesn't sound right. It seems to be a problem with the percussion instruments.

07 Ending (US Version).zip