Raven. A homemade Atari-like computer

[agranlund]

Implemented speed throttling to prevent ST emulation from running too fast.

Defender of the Crown was the very first game I had on the ST so just hearing that music fills me with nostalgia!
I hadn't used a GUI based computer before and remember not being able to start the game that first evening when the computer was unpacked - I didn't grasp the concept of double-clicking on icons until the day after when it probably happened by accident



Sampled sounds through YM are recognisable but of very poor quality due to the way the emulated machine is accessing some of the real hardware directly and others being emulated. An interesting problem to deal with some other time..

[Cyprian]

cool,

do you have SHIFTER emulation or that game is OS friendly and it works on any GFX card?

[DrZiplok]

Hmm. Those memory chips on the SIMM ain't cheap...

I'm not sure of an exact BOM cost for the motherboard, I'm guessing at €200+ excluding the IC's that are out of production?

Using the provided BoM for MLB, three 16M SIMMs and a ROM stick, as a retail US Mouser customer, $380.

[agranlund]

do you have SHIFTER emulation or that game is OS friendly and it works on any GFX card?

Yep it runs under emulation. It's a bit of on-and-off work in progress and I figure raster emulation is probably the next thing on the list.

[Oldskool]

Maybe stupid question.
Currently soldering some stuff but have a question concerning the diode direction.
Is this the correct direction (just to be sure)?

diode direction.JPG (9.93 KiB) Viewed 1341 times

[DrZiplok]

Maybe stupid question.
Currently soldering some stuff but have a question concerning the diode direction.
Is this the correct direction (just to be sure)?
diode direction.JPG

Diode orientation

Screenshot 2024-07-15 at 9.51.02 AM.png (26.89 KiB) Viewed 1286 times

From the PCB design file, front fab layer.

[Oldskool]

Thanks Herr Dr.

[Badwolf]

Is this the correct direction (just to be sure)?

I get this wrong during assembly. Every. Single. Time.



BW

[agranlund]

Note to self: Backup CF card before working on bus logic...
One very silly mistake and I found myself with a semi-trashed filesystem.
Ok, so I've been meaning to re-partition and reinstall anyway but would rather have chosen the moment myself

In better news:
Bus logic should be better and the machine can now run properly on clock configs other than 96/48mhz.
Tested with 16, 25, 32, 48 and 50 mhz oscillators in both 2X and 1X cpu multiplier modes.

Not 100% sure how to go about peripheral wait states. They are all ticking from the bus clock and are unscientifically tuned for around 50mhz, they would potentially wait longer than necessary if using a slower bus clock.
I have a spare jumper going to the cpld and I'm thinking it could be used for selecting between 50 or 32mhz tuned waitstates.

Next up would be nice to get ram burst going to feed the L1 quicker, and to reduce the dramatic cost of write-misses when copyback is enabled.
But I should probably re-install and configure Mint on my CF card first.

230, a new record for Raven

coremark.png (536.88 KiB) Viewed 1173 times

[agranlund]

I get this wrong during assembly. Every. Single. Time.

I had to cross reference in Kicad and datasheets during assembly too for this one and a few other components
Wouldn't hurt to make the silkscreen a bit clearer in some places for future revs.