Raven. A homemade Atari-like computer

[luciodra]

Emutos 1.4 is also out... :D

[Oldskool]

If the case does not have drive bay you could use a usb connector with a gotek maybe and flashfloppy. Not real floppies then. But do you really want real floppies……

[Tbs123456]

https://www.thingiverse.com/thing:1279411

Or just 3d print a drive bay adapter for the floppy/gotek drive.

[agranlund]

But do you really want real floppies……

Not really :)

I do want to make the floppy driver for the enjoyment of making it, but I don't really have much need or want to use such driver.
(which, to be fair, can be said for almost everything I code on my spare time)

[agranlund]

I spent yesterday evening disassembling the Nova driver to see if there is a somewhat clean cut between hardware driver and its VDI part.

Turns out yes!
(almost, but for my purpose good enough)

STA_VDI.PRG is, as the name implies, the VDI implementation and is near enough card agnostic. It mostly talks to emulator.prg for doing hardware stuff.
EMULATOR.PRG, despite its funny name, can be described as the hardware device driver.

With these very good news, and armed with a bit of understanding of how it works, I decided to go ahead with making a generic unaccelerated Nova VGA driver.
I think it'll be really nice to have a better fallback than the current mono situation when using card which don't have bespoke drivers.

Here's a _very_ quick and dirty proof-of-concept from yesterday.
Using my own made EMULATOR.PRG together with the original and unmodified STA_VDI.PRG from the ET4000 package.

The card here was some random Cirrus Logic I grabbed from my stash-of-cards but it'll probably work with anything that is VGA compatible, or that's the idea anyway.
I have a whole bunch of different brands and models to play with as I develop this into something proper.

nova_generic_driver.jpg

(This driver will be specific for Raven and without any consideration or support for other ISA equipped Ataris - it takes advantage of the fact that Raven can run the cards own vgabios to have them initialize themselves)

[dml]

Very cool!!!!!! :p

[PhilC]

That's spme great news, meaning we don't have to rely on obtaining the et4000 chips and can go for something comparable or even better.

I saw some gl-5436 on eBay IIRC and already have at least one S3 card somewhere

[agranlund]

@PhilC
Yeah I think it'll be a great benefit to be able to plug in any old card and get a decent experience!

The official Nova drivers are of course the better choice, especially the accelerated ones.
For now I see this as being the worst-case fallback driver. A bit like how it is/was on Windows where its built-in generic VGA driver worked with every card but you wanted to install the better, and usually accelerated, bespoke driver at first chance anyway :)


I have some ideas of how I'd like to structure support for optional accelerant drivers. Most/all of the late ISA cards have hardware blitter and I suspect it would be a great deal of fun to try and get one of them working sometime later on. In my head, the structure could end up looking somewhat like this;

EMULATOR.PRG : the base vga device driver
STA_VDI.PRG : stock from ET4000 package, provides the unaccelerated VDI.
ACCEL.PRG : optional accelerant (hooks VDI to overload or steal certain functions from STA_VDI)

[luciodra]

EMULATOR.PRG : the base vga device driver

I would like to ask a question that stems from my technical limitation regarding Atari: shouldn't emulator.prg 'redirect' the Atari video signal to the ET4000 video card?

[agranlund]

I would like to ask a question that stems from my technical limitation regarding Atari: shouldn't emulator.prg 'redirect' the Atari video signal to the ET4000 video card?

Yeah that's one of the things it does. And probably why it was named emulator.prg.

But apart from that, in the context of the ET4000 driver, it deals with almost everything that is card specific, sets up the NOVA cookie, and the API that the higher level STA_VDI is using to perform low-level things (implemented in emulator.prg) without needing to know terribly much about the actual hardware.

For all intents and purpose it's a fairly modern device-driver / high-level system split.
There is a little bit of VGA hardware code in ET4000's STA_VDI but that's generic VGA code not specific to ET4000 so for my particular purpose it's perfect -- ie; I can do just device driver code in my own EMULATOR.PRG, and not have to reinvent an entire VDI which would be years of work.