Rybags

You will usually only get a long IRG at the start of file (leader tone) when using CIO. When you write a record, the SIO output at the end should be logic 1 which is the same as the tone for IRG. You should be able to get a longer IRG by just having a delay between SIOV calls, and there should be no disruption in the leader tone. But don't use long IRG mode since it stops the cassette motor at the end of each write. Also since you're using SIOV you have the flexibility in that you can write out practically any record size that you want (I'm guessing you're probably already planning to do that) I used it in the day before I had a 1050 to create a fast loading AsmEd image - it had a loader that was a few blocks long then the entire 8K cart image was written as a single block. Also I used a VBI when writing it to increase the baud rate.

That's right - and appears to use PM objects for the vertical supports either side of the gongs. It's using Antic 6 (aka Gr. 1 ) which is only 1 colour per character cell vs 4 of 5 in Antic 4. But has the advantage of less DMA which allows the kernal to do that much, also badlines don't totally halt the CPU so there's also sufficient time to do the colour changes there as well.

The game was pretty compact in all forms - the computer version is actually only 6K on an 8K Rom.

560/561 points to the display list. You need to change the display list itself to point to your own screen Ram. In most cases display list + 4 will be what you need to change.

Location 88,89 is just the pointer to screen Ram that the OS refers to when doing character writes or pixel plots. There's also the actual screen addresses fetched by Antic which are in the Display List and you'd need to change those also. Typical Display List (560,561) will contain: 112 (3 times) 8 blank scanlines 66 LMS Antic Mode 2 (Gr. 0 ) low byte screen Ram high byte screen Ram 2 (23 times) 65 (Jump and wait for VBlank) low byte display list address high byte display list address You'd also need to ensure the screen memory doesn't cross a 4K boundary - without another LMS Antic will just wrap around and read from the current 4K block start.

The major different variant of 800XL is the later one which has Freddie. It would make sense that they use the 1-bit DRams only since we didn't see the 4-bit chips until later on in the XE lifetime.

Cool. I've looked at some of the code and documentation for this game some years back also with a view to converting it. The graphics mapping has a hardware addon that allows byte based addressing using the (ind,X) instructions - external hardware monitors the Sync pin on the 6502 and detects when certain instructions execute then modify the subsequent memory access. That alone was just about enough to turn me off attempting to do much with it. I just gave it a quick run - nice how you've set up ZXC to shoot from each base. Of course the aspect ratio isn't right but not much we can do about that other than adjust H-width on monitors that allow it. Though in fact a lot of LCDs will allow stretching a 4:3 image to fit in 16:9 which would probably make it about correct. Another thing I noticed - the sounds are practically identical. The arcade version runs 6502 at 1 MHz and supposedly it's Pokey at 1.25 which would mean that any AUDF values would need to be adjusted (and entirely possibly some poly sound esp type C would turn out very differently)

GTIA modes can only scroll at 80 pixel resolution, not 160. If done like that, character mode would be the likely avenue. But there's not really any advantage to be had here other than some extra colour. You could equally do a game in Antic 4 or 5 and just use chunky sprite movement for much the same CPU cost.

250ns is supposedly the maximul supported latency - though I don't think any DRam by that time was slower than 200.

Different numbers have been used to describe them. Supposedly 4464, 41464 and 2464 are much the same thing. I'm not sure on the exact reason, possibly when new chip carrier formats came out, or just different companies coming up with their own naming scheme.

4464 - no. That is the 4 bit x 64k DRAM. Only used by XEGS and 2/4 chip 65 and 130XE.

This appeared in my Google news feed. https://hackaday.com/2024/04/13/picontrol-brings-modern-controllers-to-atari-2600/ Not for USB controllers - just Bluetooth. But still handy as the latest couple of console generations tend to use Bluetooth.

Maybe slightly lift and reseat the major ICs. OS and Basic are the ones at top right near the serial plug (OS the bigger) Though that photo looks like not much is socketed at all?

The legacy video I would say is much the same, but entirely possible that it generates a stronger/more saturated colour signal which could affect mods that otherwise work well on a standard system. I can't recall if I tested RF on mine and probably didn't use the stock monitor port much either (600XL)

Are these components recommended for stock GTIA or Sophia usage case? By the looks of things the colour is way overdriven. Possibly the colour needs some attenuation. I don't think Sophia uses the tuning pot, it's just needed as the original GTIA uses internal delay taps which can have drift to achieve the phase delay where Sophia probably uses some sort of internal clock multiplier which would mean it's not required.