Vulcan-74 - A 6502 Powered Retro MegaProject

[Oneironaut]

barrym95838 wrote:

With all of those cool goodies and retro components, portability might be an issue ... you're going to have to gut a full-size upright piano to fit it all in!
Mike B.

Yeah, I have been considering the layout of the final design.
One thing is for sure... every single hand wired IC will be visible behind glass in some kind of hand made, back-lit wood cabinet.
I will probably go for a desktop piano configuration, with the VGA monitor built in where the sheet music stand might usually go.
Beside the monitor will be vertical columns of populated boards, nicely back-lit, and with many colored status LEDs blinking away.

Did a bit more figuring tonight, and decided to change the way the Sample Memory works.
Rather than 512K for each of the 8 voices, I am going with a single huge 8MB Sample Memory (512K x 16).
A high speed 8 channel multiplexer will swap the counters to the memory to fetch 8 samples at a time.
This way, I can assign up to 256 different samples in the huge memory, and play any 8 of them at once.
At a sample rate of 32Khz, this is 256 seconds of sample time... more than enough for a diverse number of samples.
To make this work, I just need to toss another 48 registers (74HC574) and a dozen multiplexers at it!

Did I mention that "Chip Count" is of no concern to me?

Brad

[BigDumbDinosaur]

Oneironaut wrote:

I will probably go for a desktop piano configuration, with the VGA monitor built in where the sheet music stand might usually go.

Well, if this contraption is going to look like my grandmother's upright piano it had better be able to play some Scott Joplin rags.

[BigEd]

I like a good rag! And an upright piano sounds like the ideal form factor.
But unfortunately you remind me of this: https://www.youtube.com/watch?v=a1R8Rx2db9c

[BigDumbDinosaur]

BigEd wrote:

I like a good rag! And an upright piano sounds like the ideal form factor.
But unfortunately you remind me of this: https://www.youtube.com/watch?v=a1R8Rx2db9c

Yikes! Imagine having that monster in your living room. I'll say one thing: the gentleman at the piano was certainly getting a good workout.

[Oneironaut]

My musical taste is a lot less "Loony Tunes" and a lot more Techno!
There will be no horns or tambourines in my sample list.

Brad

[Oneironaut]

Now that I have decided on a features list for the new Vulcan-74 Music Station, it will be time to rip up the blitter section and tweak the Video Generator for higher resolution. The new Video Generator will not require Sprites, but it will require a "Fast Clear" circuit to wipe the back buffer at 40MHz so that the 6502 can simply start drawing to a blank slate. I may use dual 6502s in this design - one to handle display + user input and another to handle control of the 8 sound channels.

Ironically, I figured that making a Synth / Tracker would be a bit easier than making a Game System due to audio needing much less speed, but that is far from the truth! Because I intend to share a whopping 8MB of SRAM between 8 channels, I actually need more speed, and the complexity of a bus arbiter. The C64 shares memory with 2 systems- 6502 and graphics, but Vulcan has to share memory between 10 systems - 6502, OS, and 8 audio channels!

Even chip placement is a concern now due to massive fan out. The Sample Address Switcher is going to switch a 24 bit address between 8 inputs, so it will require 24 buffers! To reduce fan-out, their outputs have to be close to the SRAM. There are several design concerns like this to be dealt with.

Anyhow I think it's only right to close this thread and start a new one, now that I am ripping up all but one row of the current design.
If the weekend offers another rainy day, I will start a new thread with another "Design Goals" list and a long winded excuse for why I am doing all of this!

Cheers,
Radical Brad

[Oneironaut]

Since I don't like welding in the rain, I had this afternoon to mess around with the VGA Generator timing.
To my surprise, the resolution has climbed from 400x300 all the way to 640x480!
I kind of figured it was capable of this resolution, and the clock only went from 20MHz to 25.175MhHz.
A video frame used to require 120K, and now it requires 307.2K (and all 19 address lines to the SRAM).

This is great, since the new Vulcan-74 Music Station will be all about displaying information.
Should have plenty of room for the 8 tracks of data along with controls, live waveform display, etc.

It was kind of sad ripping up everything right of the VGA Generator, but it was necessary.
I added a test AVR to draw a frame and a moving picture, just to see if everything was ok...


Rewired VGA Section and an empty board again!

Here is a test frame, with a single Sprite being bit banged directly by the little AVR...


Graphics look nice and crisp in 640x480.

Since I wired the end of line comparator incorrectly, my frame stretched to 720 horizontal pixels.
Ironically, the monitor did not care, and simply adjusted accordingly with 720x480 resolution.
Since that is a non standard mode, I will so0n fix the 74HC688 wiring to get back to 640x480.
For now, I just shrunk the frame to get rid of the scaling bands.


720x480 due to a wiring error in the Horizontal Comparators.

Here is a quick video showing a bunch of Logic Chips doing 640x480 VGA...

https://youtu.be/PDPH3IS0Uhg

The next small addition will be called The Fast Clear System.
This will be a set of counters that can erase the Back Buffer at 40MHz speed.
If the 6502 had to do this, it would take 3 million cycles (assuming about 10 cycles per pixel)!
So be having the hardware clear the Video Screen, the 6502 can just draw stuff each frame.

I will probably have a dedicated "Display 6502" that just handles the Video Screen.
There will be a LOT going on with graphics, to it will probably just be able to keep up.

Might be some time before I get another rainy day.
Later!

Radical Brad

[BigDumbDinosaur]

Oneironaut wrote:

Since I don't like welding in the rain...

I'm shocked to hear this.

[Oneironaut]

BigDumbDinosaur wrote:

Oneironaut wrote:

Since I don't like welding in the rain...

I'm shocked to hear this.

Ironically, it's not the electricity I dislike... it's wet gloves!
I have welded in the rain many times, and the 40 volt output of the welder is no big deal. Jut a tingle!

http://www.atomiczombie.com/Webisode%20 ... 0Rain.aspx

Sometimes the animals try to hide in my shack though.
Had a bear poke his head in on me once.

Brad

[BigDumbDinosaur]

Oneironaut wrote:

BigDumbDinosaur wrote:

Oneironaut wrote:

Since I don't like welding in the rain...

I'm shocked to hear this.

Ironically, it's not the electricity I dislike... it's wet gloves!
I have welded in the rain many times, and the 40 volt output of the welder is no big deal. Jut a tingle!

My buzz-box (an ancient Lincoln AC225) generates about 70 volts open circuit, which will give you a pretty good whack. My MIG welder, on the other hand, is about 36-38 volts maximum, which will make you jump, but not much more.

Quote:

http://www.atomiczombie.com/Webisode%20 ... 0Rain.aspx

Cool-looking bike. For some reason, I've never felt at-ease riding a recumbent bike. I'm old-fashioned and like to be upright.

Quote:

Sometimes the animals try to hide in my shack though. Had a bear poke his head in on me once.

As long as he just looks in on you yer okay.

Around here we mostly have to deal with racoons, coyotes and deer. The deer can be a real nuisance, as they come up on our deck, try to eat our flowers and then use the deck as a public restroom.

[Oneironaut]

Thanks! When I lived in the city, the lowracers were fun.
Now my roads are all massive hills and gravel, so there is no 2" high racers in my future!
I sure miss my ultra low racing trike though, that one was a blast to ride.

Now that I have chickens, turkeys, and a fruit orchard the bear will probably leave me alone, but I don't plan to share! Building a GPS controlled yard robot to take care of my fuzzy friend. Perhaps I should jam a 6502 in the control system somewhere... it worked for Bender.

Brad

[Oneironaut]

Another Blitter?.... yep!

Although this incantation of Vulcan-74 is no longer a Game System, it will still need to deal with text and graphics. Actually, it has to deal with almost three times the number of pixels per screen as the old version did (307,200 pixels now / 120,000 pixels before). Because of this serious demand, and the fact that the only chip on the entire board besides 7400 logic will be a 6502, I am going to have to add some helper circuitry to allow at least a 30 frame per second refresh rate.

Using what I learned on the previous version, I shall now create a Blitter System that will handle several functions; fast screen clearing, line and box drawing, and character drawing.

This Blitter will be a Bitmap Block Copier that will copy Bitmapped Images from a dedicated 512K buffer directly to the Video Back Buffer. Images can be any size up to 640x480, and will be stored as 8 bit data (256 colors). Since I only need lines, boxes, and characters this time, there will be no Alpha (transparent) Pixel Control, so this Blitter will actually run twice as fast as the original one I made.

Characters will be stored in the Blitter Memory as 8x8 or 12x12 (any size possible), and treated as tiny Sprites. This will allow 256 color characters and icons for a very rich looking interface to the Music Tracker Software. No clunky ROMs for mono color pixel shifting in this design! The Interface should look as good as any modern PC software, complete with 3D controls and eye candy.

Once I lay down the 40 or so 7400 Logic ICs and get the Blitter working, I will slow down and actually do schematics this time. I got ahead of myself last time and almost forgot how I made everything work! After the Blitter is tested using the AVR, I will go directly to 6502 control, and focus on VOS (Vulcan Operating System).

Since I am already posting in this thread, I will just keep it going! What's another 200 photos?... no big deal!

Sure is cool to see the breadboard pumping out 640x480 with 25 colors! I should have started this way the first time.
I remember when I first upgraded from EGA to 640x480 VGA... it was such a step up.

Does anyone know what the current record is for resolution is in a 6502 based system?
I know the BeebMaster and Acorn could do 640x256, but in only one color.
Vulcan can manage 720x480 with 256 colors, but I only use 640x480.

Retro never looked so good!

Cheers,
Radical Brad

[BigDumbDinosaur]

Oneironaut wrote:

Does anyone know what the current record is for resolution is in a 6502 based system? I know the BeebMaster and Acorn could do 640x256, but in only one color. Vulcan can manage 720x480 with 256 colors, but I only use 640x480.

I seem to recall that it was possible to achieve 640×400 in multiple colors on a Commodore 128D with the 8568 VDC running in interlaced mode. I've not seen it though.

[BigEd]

> Since I am already posting in this thread, I will just keep it going! What's another 200 photos?... no big deal!

A very long thread isn't a problem, but it's nice to get closer to one topic per thread. Otherwise the thread is misnamed, and we need to jump into the middle to find the topic change. A bit like using cassette tapes...

I do recommend starting a new thread. It's almost always the right thing to do.

[GARTHWILSON]

If it truly is another project, starting another topic would be appropriate. I don't necessarily recommend starting another one just because one is getting long though, since it means those who have commented before, who are interested but don't check in often, will no longer get email notifications when there are new posts.