GR8NET OPL4 support

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By SjaaQ

Master (247)

SjaaQ's picture

01-11-2021, 10:42

Eugeny Brychkov created new firmware (addition) that enables the GR8NET to be compatible with the OPL4 as well.

Check out the video at:

You need to upgrade your general firmware to 0.12, flash another additional firmware for OPL4 compatibility and of course the YMR801 rom.

The version in "test-images" dated 2021-10-26 has a fixed issue about high pitched noise, it is highly recommended and also used in this guide.

Quick update guide:
• _FLINFO and check if you have the W25Q128FV chip (16MB). If you don't, you cannot use this firmware.
• Check if you have version 0.8 or higher using _NETVER. If you don't you first need to upgrade to 0.12 with a hardware flasher.
• Press enter on "update.asc" to update everything to 0.12
• Power cycle (with cursor down pressed)
• Check if you now have version 0.12 using _NETVER
• Check your serial flash free sectors with _FLLIST
• Press enter on the "gr8net-fpga-reg.bin " image
• _FLUPDATE(0) (note: this updates the genenal0 firmware to a bugfixed version)
• Power cycle (with cursor down pressed)
• _FLLIST to list free sectors. You probably just have the MP3 firmware at sector 4, sector 8 and higher are free.
• Press enter on the "gr8net-fpga-opl4.bin" image
• _FLUPDATE(8) to write to sector 8 (or another free 4 sectors)
• Press enter on the "gr8net-opl4r.asc" basic program.
• The program will ask the free sector to write the OPL4ROM to. In the default state, this could be sector 12. It needs 32 free sectors).

Now you can switch to the OPL4 firmware using _NETRECFG(8). When booting press TAB to select the OPL4 mode (combination of Nextor, OPL4 memory and main memory). Option 3 selects Nextor, 512MB of main ram and 512KB of OPL4 ram.

• The OPL4 firmware does not support any other hardware so all GR8NET basic commands are gone.
• Do not flash the OPL4 firmware to sector 0. You know, you GR8NET commands are gone.
• To get back to the default firmware, power cycle.
• If you want 1MB of OPL4 ram, select option 2 at boot, but you will need another device to boot DOS2 from.
• When using MAPDRV note the Nextor rom has moved from extended slot 2 to 0.

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By Wolverine_nl

Paragon (1159)

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01-11-2021, 12:19

I saw his video on this, gonna try this soon.

By alexito

Paladin (747)

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02-11-2021, 11:18

@Wolverine_nl: Me too and thanks for the news.

By Grauw

Ascended (10158)

Grauw's picture

02-11-2021, 11:33

That’s pretty cool, and a first for FPGA emulation of OPL4!

By SjaaQ

Master (247)

SjaaQ's picture

02-11-2021, 13:49


The thing is, I still have 212 sectors free. What else could there be put in there?

I'd like to see a SN76489 as well.

Note the current firmware seems to have been replaced with the bug-fixed versions from test-images.

By SjaaQ

Master (247)

SjaaQ's picture

03-11-2021, 11:19

I also asked Eugeny how he did the OPL4 FPGA firmware:


I had experience with OPL (Y8950) and OPLL in the past. OPL4-FM is the same as OPL3. OPL4-PCM is actually very easy (I have extensive scream tracker experience). And of course a lot of testing comparing output of real chip to what I have designed.

So even more impressive!

By Vampier

Prophet (2386)

Vampier's picture

03-11-2021, 16:42

booohoooo - I don't have a new enough GR8net

By Wlcracks

Champion (442)

Wlcracks's picture

03-11-2021, 17:05

Vampier wrote:

booohoooo - I don't have a new enough GR8net

Maybe its possible to upgrade? You could send Eugeny an email for the possibilities.

By Pencioner

Scribe (1480)

Pencioner's picture

03-11-2021, 17:08

Vampier wrote:

booohoooo - I don't have a new enough GR8net

I have upgraded mine some time ago by replacing a flash chip (was quite an adventure with my skills as it is SOIC8 one) but if you solder or have someone who do that - it is very doable Smile

By SjaaQ

Master (247)

SjaaQ's picture

03-11-2021, 20:35

From the manual:


...thus to use older GR8NETs with this image you need to upgrade EPCS16 chip to W25Q128FV.

So I would say that is possible.

Also, the EPCS16 is 2MB, so you can still write the OPL4 firmware (4 sectors) but you will not have the YRW801 rom. You would still theoretically be able to play MOD files for instance or FM only. I am not sure if the firmware checks for the YRW801.

You only need 8 sectors for the general0 firmware at sector 0 and 4 more for the OPL4 firmware (and the chip has 32 sectors, but you can check with _FLLIST on firmware 0.12).

By sdsnatcher73

Prophet (2337)

sdsnatcher73's picture

03-11-2021, 21:00

You could try removing the MP3 firmware if you don't use it.

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