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AlarCity - for Vampire?page  1 2 3 

Andy Hearn

Posts 288
04 Jan 2018 15:32

sorry, I was just thinking of the potential "raw" speed of both a:-
OCS 16bit bus @ 7Mhz = ~13.3Mb/s
AGA 32bit bus @ 14mhz = ~53.4Mb/s

never mind:-
agnus blocking every 'odd' clock cycle for system access, only potentially allowing cpu bus master on every 'even' clock.
Copper/Blitter/DMA have priority to steal more 'even' cycles if needed,
Large/deep screen modes take additional 'even' cycles if needed to get data out to Denise and the DAC for display

so the 3.5meg/s for ECS/OCS and 7meg/s for AGA is representative of real world CPU to chip speeds. though I have seen 14Mb/s in some edge cases of hardware I seem to recall.

but even so. from just developing for an 020+AGA platform, I would say that these numbers make the vampire's implementation of the AGA chipset even more interesting, as ram access? not even a thing to stress about! :D

Gunnar von Boehn
(Apollo Team Member)
Posts 4737
04 Jan 2018 16:48

Andy Hearn wrote:

  sorry, I was just thinking of the potential "raw" speed of both a:-
  OCS 16bit bus @ 7Mhz = ~13.3Mb/s
  AGA 32bit bus @ 14mhz = ~53.4Mb/s

The memory is clocked the same MHz on both.
And memory can accessed at most every 2nd clock.

This means:
  OCS 16bit = 7 MB/sec
  AGA 32bit = 14 MB/sec 

Of this the CPU can at maximum use 50%.
So CPU max are 3.5 MB/sec and 7 MB/sec

* The AGA Bitplane DMA can do "double-fetch",
if enabled this raises the peak DMA Bitplane DMA to 28 MB/sec for AGA.

Andy Hearn

Posts 288
04 Jan 2018 17:04

aaaaaah haaaaa.... I knew the 50% thing, I just didn't realise the AGA chipram was clocked the same.

so an A1200 is a 14Mhz EC020 sat on 7Mhz ram. could they cripple it any more? no wonder the CPU danced when you plug in some fast ram!

Mr Niding

Posts 444
02 Feb 2018 19:59

Reminding people about this game;


Billy Nest

Posts 30
11 Feb 2018 20:01

This game is a must buy Vampire or not. I would love to see a Vampire RTG version too if this is possible. Vampire community is growing very fast And V4 is at the door for the next years.

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