ECS Denise.. is it worth it ?

[SimonV]

What I would like to see is a "denise-switcher" like you have kickstartswitches. switching between ECS and OCS would be nice . I can use the ECS resolutions for my workbench on my multiscan, and switch to OCS for the old games.

And do not tell me to buy a graphicscard, I am talking about my A500

[Piru]

@Nostalgiac

Productivity isn't exactly standard VGA, but it's often close enough. If not, there's "VGAOnly" that is supposed to modify it closer.

[AmigaHope]

OCS Denise had half-brite mode, except for the revisions in the earliest shipments of A1000s (I forget the rev # that added EHB). I believe that you can still open EHB modes on the  original Denise, but you won't actually get the half-brite effect.

The high pixel clock (35ns) modes on ECS Denise weren't any slower than 16-color hires modes on OCS/ECS, because they limited you to 2 bitplanes instead of 4, thus keeping the bandwidth the same. ECS didn't actually add any faster fetch modes to OCS, so the bandwidth limitation remained.

AGA added faster fetch modes, which is why you can have 8 bitplanes at all pixel clocks.

[LoadWB]

Maybe that's what I was thinking, then, was Extended Half-Brite.  It's been sooooo long!  I've been on AGA for five years and a graphics card for two.

Does anyone have HB vs EHB info off the top of the head?

[Piru]

@LoadWB

Does anyone have HB vs EHB info off the top of the head?

HB is just shorter name for EHB.

[Piru]

@AmigaHope

The high pixel clock (35ns) modes on ECS Denise weren't any slower than 16-color hires modes on OCS/ECS, because they limited you to 2 bitplanes instead of 4, thus keeping the bandwidth the same.

Yeah. 16 colour hires is painfully slow, too :-D

[Brian]

@Zac67
I stand corrected... Knew SuperHires came with ECS but thought also 64 color mode for paintprograms requiered ECS but just verified with WinUAE that this was infact incorrect of me.

[AmigaHope]

@Aminicle

ECS Denise is 100% compatible with software and screenmodes designed for OCS, you wouldn't actually need to have both an OCS Denise and ECS Denise on a switchboard like the Kickstart switchboards.

Just open your Workbench and stuff in high scanrate modes. When you start up your old games, they'll open up 15Khz screens just like normal (though you might need to change monitors or add a monitor switch).

[AmigaHope]

@LoadWB

EHB == "Extra HalfBrite". When I say "half-brite" I'm talking about EHB. They're the same thing.

And like I said, EHB is in EVERY Denise, from OCS to ECS, and in AGA Lisa. The only exception is in the *VERY FIRST* revision of OCS Denise in some A1000s shipped in 1985.

EHB was added to Denise not long after, so lots of A1000s support EHB. If you have one of the very early Denise revisions in your A1000 that do not support EHB, you can swap it out for a later OCS revision Denise that supports it.

You might even be able to put an ECS Denise in an A1000, but I don't know if you would be able to do much with it as you can't fit an ECS Fat Agnus in the A1000. (A1000s use the original "thin" Agnus which comes in a DIP package rather than PLCC. ECS Agnus was only ever released in PLCC Fat Agnus form, so there is no upgrade possible.)

I think it *might* be possible to enable the ECS Denise 35ns  pixel clock and variable horizontal scanrate without having an ECS Agnus, but since Agnus controls the DMA clock (and thus the vertical sync) you would be limited to the same vertical refresh rates, and line doubling might not work. My guess is that AmigaOS would refuse to let you try it anyway and you'd have to resort to hardware banging to enable any sort of ECS screenmode.

[AmigaHope]

@Piru

Piru wrote:
Yeah. 16 colour hires is painfully slow, too :-D

Well, it's SOMEWHAT faster than 16-color hires, actually. The DMA bus contention is exactly the same as 16-color hires, but for a given graphical operation the CPU is writing only half as much data.

Basically the speed is exactly same as opening a 16-color hires screen but only writing to 2 of the 4 bitplanes.

So in interactive GUI use a 4-color Productivity/DblPAL screen feels about as fast as an 8-color 15Khz Hires screen, or 33% slower than the equivalent 4-color 15Khz Hires screen. (Double Denise DMA traffic but Blitter DMA and PIO traffic stays the same at same color depth).

Edit: This is an oversimplification, I should point out. In OCS/ECS the CPU gets the same amount of bandwidth to chipmem  no matter what. CPU writes to chip memory on a 2-bitplane screen will always go twice as fast as a 4-bitplane screen provided there is no blitter activity. The blitter, however, gets extra bandwidth from unused Denise DMA cycles, so things like moving a window and text rendering, as well as other typical blitter-accelerated GUI operations, will go faster when you have less Denise DMA traffic.

Generally though I think for the way most GUI operations "feel", the (ECS) 4-color 35ns DblPAL 640x512 == 8-color 70ns PAL Hires 640x512 is a good comparison, but if you use a patch to replace blitter functions with CPU block moves, then all the 4-color modes will actually feel exactly the same (although theoretically you're wasting the few DMA cycles that the blitter could be using that the CPU can't get at).

[Zac67]

I don't think, Denise' ECS features could be used with an OCS/A1000 Agnus - Agnus controls the chip bus and probably has to know a bit about the data being moved. Since vertical blanking depends on Agnus (as horizontal does on Denise), the most you could theoretically get out of it would be SHires.

Running these 'ECS modes' with maximum color depth (2 planes) will be painfully slow without fast RAM (16 or 32 bit). Denise' DMA cycles will use up >75% of bandwidth, pretty much starving the 68k & blitter. Even with fast RAM any manipulation is pretty slow, no comparison to AGA or even a graphics card.

[AmigaHope]

@Zac67

I think you could MAYBE coax a DblPAL-type mode out of an OCS Agnus/ECS Denise system... You'd set the pixel clock for 35ns pixels and double the horizontal refresh (I think Denise could force a horizontal blank without Agnus knowing about it)... and you'd keep the vertical blank the same. I really have no idea if Agnus has to cooperate with Denise on horizontal blanks (though I think you can free DMA time on the horiz. blanks so I guess there must be a capacity for Agnus to know about them). I really don't know enough about the internals to say for sure.

Denise at its maximum doesn't eat up much in the way of the CPU's allocated chip mem bandwidth, but at that point any *OTHER* DMA you do (particularly with the blitter) starts seriously hogging the bus away from the CPU.  By itself a 640x512x2bppx50Hz DblPAL screenmode eats just shy of 4 megabytes/sec of bandwidth. A1000/A500/A2000 chipset has roughly 3.5Mbytes/sec bandwidth dedicated to the chipset, and another 3.5Mbytes/sec that the CPU can use. You're not really stealing that much.

Once you start blitting stuff around a lot though, it eats up even more bandwidth and slows the graphics system down to a crawl (and basically kills the CPU if you have no FAST RAM). This is why CPUBlit-type patches speed up the system so much on high-bandwidth screens.

This goes double for A3000 ECS systems and AGA systems that give the CPU 32-bit paths to chip mem. Once you've eaten up the dedicated custom chip bandwidth, the blitter becomes a drag on the system rather than a benefit, as long as you have CPU cycles to spare.

Anyway the ECS 2-bitplane 35ns modes aren't so bad performance-wise, provided you have real fastmem and don't try to use the blitter. On the A3000 with its 32-bit chipmem  they're actually VERY nice if you don't like the fringing motion effects that you get on deinterlaced screens.

[Nostalgiac]

gosh - thanks to all - so much information :-)

I thought I knew the Amiga quite well once upon a time, but it seems there's a lot of stuff that came after I (tmp) left the scene  ;-)

I guess 9 euros are worth the gamble - it would really save a lot of space if I can chuck the 14" monitor back into the loft.

cheers !
Tom

[Zac67]

@AmigaHope

I think you could MAYBE coax a DblPAL-type mode out of an OCS Agnus/ECS Denise system... You'd set the pixel clock for 35ns pixels and double the horizontal refresh

This is what would have to be done - but I'm not at all sure if Agnus buys it.

(I think Denise could force a horizontal blank without Agnus knowing about it)... and you'd keep the vertical blank the same.

The whole 'DMA' timing is based on horizontal scan lines and controlled by Agnus (it's no real DMA since chip RAM is Agnus local memory actually, the CPU is DMAing) - you might be able to trigger horizontal and even vertical blanking with Copper - but AFAIK it's questionable whether (old) Agnus resets to a new scan line as well.

I really have no idea if Agnus has to cooperate with Denise on horizontal blanks

Agnus is doing ALL memory access for chip DMA and passing the data to the appropriate targets (Dave Haynie has written some very enlightening info about this in the unfortunate '8 MB chip RAM in A4000' thread), so it's absolutely essential that Agnus knows about what to do.

(though I think you can free DMA time on the horiz. blanks so I guess there must be a capacity for Agnus to know about them).

I don't really get the point here.

Denise at its maximum doesn't eat up much in the way of the CPU's allocated chip mem bandwidth, but at that point any *OTHER* DMA you do (particularly with the blitter) starts seriously hogging the bus away from the CPU.  By itself a 640x512x2bppx50Hz DblPAL screenmode eats just shy of 4 megabytes/sec of bandwidth. A1000/A500/A2000 chipset has roughly 3.5Mbytes/sec bandwidth dedicated to the chipset, and another 3.5Mbytes/sec that the CPU can use. You're not really stealing that much.

Running Hires/16 colors or SHires/4 colors uses ALL available chip RAM bandwidth during scan line (7 MB/s). The only access Copper, Blitter and CPU (in that order) get is during horizontal/vertical blanking (Paula and floppy are real time and have reserved time slots). If severe overscan is used, all operations slow to a crawl.

Once you start blitting stuff around a lot though, it eats up even more bandwidth and slows the graphics system down to a crawl (and basically kills the CPU if you have no FAST RAM). This is why CPUBlit-type patches speed up the system so much on high-bandwidth screens.

This goes double for A3000 ECS systems and AGA systems that give the CPU 32-bit paths to chip mem. Once you've eaten up the dedicated custom chip bandwidth, the blitter becomes a drag on the system rather than a benefit, as long as you have CPU cycles to spare.

But only if the CPU has 32 bit access to chip RAM (A3000/1200/4000) since even the AGA blitter works only on 16 bit at a time and actually wastes bandwidth. On A500/600/2000 systems you can't gain much, esp. w/o fast RAM.

Anyway the ECS 2-bitplane 35ns modes aren't so bad performance-wise, provided you have real fastmem and don't try to use the blitter. On the A3000 with its 32-bit chipmem  they're actually VERY nice if you don't like the fringing motion effects that you get on deinterlaced screens.

Actually the A3k's chip RAM isn't 32 bit, only CPU access is. ;-) (It's got two banks and the CPU can access both banks simultaneously, somewhat like modern dual channel chipsets that can access two 64 bit channels as 128 bit.)

Of course, deinterlacing is a different problem, but on my A3k I've used NTSC interlaced (flicker reduced 60 Hz instead of PAL) much more than Productivity - before I bought my Merlin graphics card that is. :-D

[AmigaHope]

@Nostalgiac

Well it's not going to help at all with games. Having full ECS will mean you can tweak your existing screenmodes though so that your flickerfixer can output modes that your monitor can handle, plus let you use 4-color ~31Khz modes directly.

Once you get the Super Denise installed, you should edit your screenmodes (stored in the Monitor files) so that your regular  screenmodes wind up at frequencies that your monitor can support. i.e. tweak your 15Khz modes so that your scandoubler/flickerfixer generates useable doublescanned modes. You are probably going to want to use more than the 4 colors that the native 31Khz ECS modes can do. XD

And again, this will not do diddlysquat for games. For that stuff you just need to get a better monitor that can handle a doublescanned PAL screenmode. =p