Booster clock switching + DMA nerding

[JezC]

@Badwolf I'll be interested to know if/when you think you have a final solution/version to test...

I think I do now, but it requires some physical modifications which I need to document. A new revision is probably on the cards.

If you're happy to cut a few traces and wire in a few bodges, then I'd be keen to get additional feedback.

BW

Yes, I'll probably finish the original build & briefly test it & then do the mods once know it's basically working.

No rush, just update us when you can! Thanks.

[Badwolf]

I think I do now, but it requires some physical modifications which I need to document. A new revision is probably on the cards.

If you're happy to cut a few traces and wire in a few bodges, then I'd be keen to get additional feedback.

BW

Yes, I'll probably finish the original build & briefly test it & then do the mods once know it's basically working.

No rush, just update us when you can! Thanks.

If you've not yet put on the socket strip and the pin headers, it's easier to cut the traces.

Basically you need to:

* Cut BG to BG on the headers (tiny trace between DIP64 pins 11.
* Cut the VCC line going to the CKE pin on the SDRAM (the short 45 degree trace to a via coming out of pin 37 on the RAM chip)
* Run a bodge wire from the BG line going to the motherboard to TP4
* Run a bodge wire from the BG line going to the CPU to TP5
* Run a bodge wire to the CKE pin on the SDRAM chip to TP3

Here's how I did it:

IMG_8002.jpeg (356.16 KiB) Viewed 2233 times

IMG_8003.jpeg (333.61 KiB) Viewed 2233 times

TP1 remains the TOS 2 decoder.
I've a plan for TP2, but probably only @coonsgm would be interested in that...

BW

[coonsgm]

What is this I would be interested in??? TP2 you say...

[agranlund]

What is this I would be interested in??? TP2 you say...

TurboPower2 ?

[coonsgm]

What is this I would be interested in??? TP2 you say...

TurboPower2 ?

Well then, I am 100% for more power. Turbopower is just that much better.

[JezC]

@Badwolf I'll dig out the board & check if I'd soldered the socket/headers on or not...been so long I honestly can't remember!

[Badwolf]

TurboPower2 ?

Well then, I am 100% for more power. Turbopower is just that much better.

Haha.

No, TP2 is Test Point 2. DSTB has five test points and four have now been co-opted by other functions, but TP2 appeared available.

I had it in my mind that you talked about measuring the effectiveness of accelerators on games in one of your videos -- or perhaps it was in a forum post. Anyway, one of my old dev boards pulsed a line when a write was made to the video shifter registers. Implication being that a double-buffering switch was occurring. I thought I may add that to TP2 on DSTB1 by default.

With a suitable frequency counter, it lets you measure the instantaneous FPS of any double-buffered game. Just set up a vaguely stable and repeatable section of play and note the frame rate. Try again with the booster.

8MHz STRAM:

IMG_8015.jpeg (191.4 KiB) Viewed 2098 times

16MHz ALTRAM:

IMG_8014.jpeg (193.14 KiB) Viewed 2098 times

8MHz STRAM:

IMG_8012.jpeg (187.09 KiB) Viewed 2098 times

16MHz STRAM (game doesn't support running in AltRAM):

IMG_8011.jpeg (193.76 KiB) Viewed 2098 times

We can therefore conclude Stunt Car Racer isn't really CPU limited and is memory limited instead. It would need a patch to let AltRAM kick in, or a MSTE-style cache to get much boost.

Frontier, OTOH, because it supports AltRAM (by accident -- hard coded frame buffer addresses), gains a healthy boost.

BW

[coonsgm]

This is an awesome way to technically measure the performance goodness and better understand where the bottleneck is in the system.