Looks like I'll be getting a Mega ST4 soon

[rubber_jonnie]

I'm sure some of you will cringe seeing this thread pop up again, but no, the Mega4 still lives and just got a minor upgrade

My erasable 27C4096s arrived and after a run through the eraser, I tested them all with my first effort at a dual ROM, and have dropped one into my Mega 4, specifically in the V1.1C IDE board.

I can now boot from IDE in either TOS 1.04 or TOS 2.06, and I'm really pretty stoked at the success of my first go at a dual ROM. All I need now is to find a switch so I can switch between them and it's actually complete!!

In time I will get some OTP ROMs, as the erasable ones are way too useful to leave in a machine

[Tomswork]

Excellent

Tom

[PhilC]

Just be careful with the pins on those eprom. They don't have the usual grooves in the base of the chip that helps to keep them in the right place.

[rubber_jonnie]

Just be careful with the pins on those eprom. They don't have the usual grooves in the base of the chip that helps to keep them in the right place.

Yes, I'd noticed, and one needed a little tweak!

[Tomswork]

Screenshot_20200522-134348_eBay.jpg (105.15 KiB) Viewed 3892 times

I got this adapter works great for 27c4096 but pin 2 is fickle with my tl866

Tom

[rubber_jonnie]

I got this adapter works great for 27c4096 but pin 2 is fickle with my tl866

Tom

My TL866 came with about 5 adapters, but the PLCC 44 one didn't work initially and I had to fix it as 2 pins weren't actually connected that should have been.

[derkom]

My TL866 came with about 5 adapters, but the PLCC 44 one didn't work initially and I had to fix it as 2 pins weren't actually connected that should have been.

They're connected correctly, but for PLCC44 programmable microcontrollers, not for PROMs.

[rubber_jonnie]

My TL866 came with about 5 adapters, but the PLCC 44 one didn't work initially and I had to fix it as 2 pins weren't actually connected that should have been.

They're connected correctly, but for PLCC44 programmable microcontrollers, not for PROMs.

Ahhh, that would make sense.

[rubber_jonnie]

I've been toying with the idea of adding a front panel switch to my Mega4 since installing @exxos IDE v1.1C adaptor.

Since I got my erasable 27C4096 ROMs, I'd made my first dual boot image with TOS 1.04(IDE patched)/TOS 2.06 and was pretty happy with the results, but today I decided to go one further and created an image with EmuTOS 0.9.12 and TOS 2.06.

As per usual once I'd created the ROM in HxD and saved the image, I then used Cartman to byteswap the image since this is necessary to work with my TL866II+. I've attached both the standard and byteswapped (Marked _BS) images for anybody that wants them, since EmuTOS is open source and TOS 2.06 is freely available.

Here is the new switch (I won't bore you with how to install it, it's 3 wires!), I need to do neater labelling, but it's good for now:

Mega_Front.jpg (71.86 KiB) Viewed 3767 times

And before I have a bunch of comments about 'How could I cut my Mega4 case like that?', that was how it arrived when I bought it. I'm highly likely to paint the Gotek mount a matching grey at some time in the near future so it looks a bit nicer.

Booting to EmuTOS:

EMU_Boot.jpg (92.92 KiB) Viewed 3767 times

And finally at the EmuTOS desktop:

EMU_Desk.jpg (134.81 KiB) Viewed 3767 times

Of course this doesn't need to be a final configuration, a ROM swap and label change is all I need for some other config. I'll get some proper OTP ROMs soon too, as the erasable ROMs have quite a poor design and it's easy for the pins to get knocked out of kilter.

Interestingly, @terriblefire had mentioned about EmuTOS not needing the connection to the ACSI IRQ line that is needed for TOS 2.06 and IDE. I deliberately disconnected the IRQ line and EmuTOS boots 100% with no problem from IDE without the IRQ line present. It also used it's own internal IDE driver and there was no sign of HDDRIVER loading during boot.

Also, running XFRRATE.TTP under EmuTOS gave a fastest (RWABS) result of 1120kb/s, whereas under TOS 2.06 with HDDRIVER with Blitter acceleration the fastest result was 1540kb/s (RWABS). I know that even with Blitter acceleration disabled HDDRIVER comes in just over the 1300kb/s mark, so EmuTOS clearly doesn't have quite the performance levels under IDE.

[PhilC]

@rubber_jonnie thanks for sharing the tos files, you've beat me to it so I shall borrow yours instead of making my own