FastRam block copy new commands thoughts

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exxos
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FastRam block copy new commands thoughts

Post by exxos » Sun Jun 03, 2018 9:31 pm

I was actually wondering about doing some sort of simple blitter internally in the PLD logic to block copy data or clear data in fast ram...

The thought came around in light of recent booster ideas of copying ROM to FastRAM via the PLD logic alone. Pretty much the PLD would copy and write data at the same time.. Not so simple with fastram to fast ram copy.. was still actually possible..

Basically what we would have is a start register, end register, and block size register. Where the PLD do the copying direct to and from fast ram and the CPU is only used to program the three registers. It will be a lot faster (aka less clock cycles) to do a copy this way rather than using the CPU..

Similar, a block clear could be done extremely fast by the PLD logic. Basically how it would work is a counter internally in the PLD is just set with the start address, and it would count up from this address according to the block size register. As the fast ram will be 10ns speeds, a block wipe can be done extremely fast. Obviously a block copy could be done pretty much with the same counters internally..

The question is, would such new functions be useful or even be used in future or current software ?
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Petari
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Re: FastRam block copy new commands thoughts

Post by Petari » Sun Jun 03, 2018 9:52 pm

I think that this is great idea, and I guess that will not need too much work.
Surely can help some SW.
Example: Great Giana Sisters on ST without blitter - whole graphic draw is based on block copy. If put level data in Fast RAM, can copy it in this way much faster to video RAM.
Yes, I know, you talked about Fast RAM to Fast RAM copy - but probably can solve Fast RAM to ST RAM - and it should be faster just because faster read, and not using CPU - little faster than with blitter ..
Fast RAM to Fast RAM can be good for sure, fast clear too. But I know only graphic code where could benefit from it. Surely can be useful in many other cases, it's only that there is not much new SW developed except games, as I see.
In some C compiler, where there is block copy command, could be useful :idea:
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Re: FastRam block copy new commands thoughts

Post by exxos » Sun Jun 03, 2018 9:58 pm

Yeah graphics will make use of faster functions, but at the moment ST-RAM is bottleneck until new MMU is developed.

Its why I start thread, as Lots of copy/clear can be done in fast-ram super quick, but the CPU (maybe blitter has access to fast-ram not sure?) would still need to block copy to video ram..

I'm sure a lot of post-processing could be done in fast-ram , then block copy that to ST-RAM.. I guess really need "super blitter" but I am not there yet and just looking for possible simple functions I could add in current booster PLD logic.

A thought would be things like sprites, fast-ram copy for many sprites , then copy 32K screen buffer to ST-RAM.. This way sprite processing always done in fast-ram. Really could have 1 or 100 sprites copy on fast ram frame buffer without to much speed loss anywhere.
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Re: FastRam block copy new commands thoughts

Post by exxos » Mon Jun 04, 2018 12:14 am

Actually, if I ditched the Atmel PLD and went for Altera one, I could program the suska blitter core into the same PLD as the booster...

I guess it depends on if the suska blitter can access the full ram range and run at 50MHz...
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

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Re: FastRam block copy new commands thoughts

Post by Petari » Mon Jun 04, 2018 9:25 am

Original Atari can access low RAM at address 8, and can access for instance IDE port - what is at other end of 24-bit address range. So, I'm pretty sure, that it can access any RAM area between 0 and $E00000, and ROM too. I did not test is specifically, but that's easy to do. And disabling access to some area would be actually just + logic in chip, without any sense. So, yes - blitter can transfer to/from Fast RAM.
There is 2 kind of people: one thinking about moving to Mars after here becomes too bad, the others thinking about how to keep this planet habitable.

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