exxos's Atari, Amiga & retro forum

I’ve finally acquired a Mega ST 4, the machine which as a 1040 STFM and later 520STE owner in the late 1980s I always wanted because of its separate case / keyboard and internal expansion bus. I must admit I was disappointed it didn’t come with a 68020 with sockets for 68851 and 68881. Having finally got one, would this be a reasonable expansion pathway?

* internal UltraSatan hard drive
* ATW 800/2 primarily for graphics, secondarily for playing with Helios
* some form of Ethernet / USB port for file transfer
* a 68030 / 68881 expansion card with extra RAM, partly for MiNT, partly to see if I could get 68k Unix / Linux running.

Secondly, what would be the best 68030 / 68881 expansion card? The purist in me would like the 68020 / 68851, but the MMU coprocessor seems to be unobtainable, so 68030 it would be.

I'd probably go for an ST536 if it were in stock: https://www.exxosforum.co.uk/atari/store2/#0220
If not an ST536, go for a standard Amiga TF536 and flash it with the ST firmware... this'll give you 030 with fast-ram. (Perhaps the builder would flash it with ST firmware if asked, there are various different builders on this forum in the Amiga section)

And a NetUSBee for USB/Ethernet...

TF536 (does not have 68882) or even PiStorm. TF534 have 68882 but doesn't handle that much memory if I remember correctly (4Mb max?). PAK68/030 is hard to find with FRAK and PuPla. There is 68881 expansion card for the MegaBus made by Atari but they are also rare.

NetUSBee for Network/USB on the cartridge port. Otherwise Lightning-ST with a PicoWifi. Lightning-ST have IDE interface as well for HDD so you don't have to buy UltraSatan. Get a IDE2SD. Or Hydra on the cartridge port.

There is Nova for ISA gfxcard. But ATW800 would probably be more fun. Both uses the MegaBus.

Does the NetUSBee work with the TF boards? Some accelerators don't work with it.

A NetUSBee won't work with the Pak 68/3 boards, for example.

I'm happy to report that the SidecarTridge does work with the Pak 68/3 though. :)

I'll second @Dog about the Lightning ST - I have one in my Mega ST4 and it's great.

Thanks everyone for the very helpful comments. I’ve put my name on the list for the next run of ATW800/2 boards since it offers enhanced graphics, and the intriguing Helios operating system. Lightning definitely looks good. It’s been 35 years since I graduated with my electronic engineering degree and I haven’t worked as an engineer since the last century so if I’m going to design my own 68030 / 68882 / fast RAM board I’m going to have to hit the books hard…

My MegaST here has the following upgrades

1) Sidecartridge MultiDevice. Amazing device offering HDD, FDD, USB, and the lastest micro-firmware offers Wifi
2) ACSI2STM. The best value HDD solution for STs IMO. Very stable. Ok speedwise. The MegaST kit offers an internal mounting kit.
3) RGBTOHDMI - Raspberry Pi Zero W + Shifter Pickup board + Audio ADC = Pixel perfect output and stereo sound (NOTE: You may want to change the PSU as shifter is partially under PSU)
4) ATW800/2 MegaBus Transputer + GFX card

Alex, quick question on the HDMI audio board for the RGB2HDMI mod?

I have one here, just haven't installed it in my STacy yet but I was under
the impression that it brings the sound out, but it's still just the usual
ST "mono" sound.

Did I misunderstand that? Does it do something to make the ST's mono
sound into true stereo?

Thanks much.

I second the SidecarTridge. I have one here, using it with my STacy
and it's an amazing device. A literal "Swiss army knife" for your ST.

:)

Darklord wrote: 01 Sep 2026 20:30 Alex, quick question on the HDMI audio board for the RGB2HDMI mod? I was under the impression that it brings the sound out, but it's still just the usual ST "mono" sound.

It is a dual ADC so it does support two inputs. It all depends how you connect it to the ST.

Darklord wrote: 01 Sep 2026 20:30Does it do something to make the ST's mono sound into true stereo?

IIUC you can wire it up for stereo but it means bypassing the motherboard mono mixer.

NOTE: The technique of playing samples with the YM2149 doesn't work (or sound correct) with a stereo sound mod.

Okay, thanks Alex.

I did already know that, like the Tweety Board, some samples/sounds
don't sound correct when changed this way. I think that's why some
people had put a switch on the various Tweety Board versions so they
could turn it off when sound was affected.

I had done that cheap 'n easy audio mod on my STacy, just bringing
the sound out via an RCA jack, then playing it through an LG Xboom
box, which takes mono sound and simulates stereo sound from it.

That sounds surprisingly good.

Going by this though, I guess I might want to look at actually installing
the HDMI audio board on my setup.