02 August 2018, 21:22 | #81 | |
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02 August 2018, 22:06 | #82 | |
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Had Commodore released a system where the CPU had similar bandwidth to Chip RAM as Lisa had, it would have been far more capable of 3D games like Doom/Doom II, especially with an accelerator added. Not a very Amiga-like solution, but would've worked a treat in the short term. Chunky GFX would've been great too, but overall less important. |
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03 August 2018, 02:49 | #83 | |
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03 August 2018, 10:07 | #84 |
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We can speculate all we like, but one thing would've killed the Amiga stone dead even if Commodore HADN'T gone bust:
The Sony PlayStation Honestly, the Amiga was being hammered by the PC and consoles of the time, and the PlayStation absolutely hammered the PC and consoles of the time. Simples. Put simply, in 1994 and early 1995, there was no PC that could stand up to the technical prowess of the Sony console, so how on earth would the Amiga have been expected to compete? Face it, it's the march of progress, and these pieces of hardware had their time. All we can do is dream how things could've been better (and boy, they certainly could have been instead of the business-obsessed, money-grabbing, inept-minded and short-sighted Commodore execs that ruled the roost after they kicked out Tramiel), and, short of inventing a time machine and going back to the 80s and making everything right with the Amiga, there's not a lot we can do about it. In any case, the Amiga would've had a natural end to the series anyway, if Commodore hadn't gone bust. They released the original hardware (OCS), a step-up (AGA) and they would've released their ultra-advanced hardware... and then that would've been it. And I heard this from Dan Wood of Kooky Tech, so ask him. |
03 August 2018, 10:28 | #85 | |
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None of this casts shade on what a great machine the Amiga is and there were some real hardware pushers and good games that came out in the latter period in late '93 / '94. For Commodore and the Amiga to have had a fighting chance of keeping a pace the A1200 should have been out by October of 1990 to compete comparably well with the Mega Drive and SNES - AGA may not have compared to the SNES's graphics but with a couple of years on the market, devs would have been more familiar with AGA and working around some of its limitations just as they did with OCS/ECS. After that Dr Ed Hepler's Hombre based CD console in 1994 may have kept a pace with the PSX. And all the above somewhat depends on Commodore management not being total cockwombles. |
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03 August 2018, 13:22 | #86 |
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A Commodore console wouldn’t/couldn’t have competed with the PSX, but a Hombre Amiga computer would have not been in competition with it, it always confuses me when people say the PS1 would killed everything at that time, simply not true as obviously PC’s and Mac’s lived through that era, and if the Amiga fanbase and Commodore kept going they would have too.
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03 August 2018, 13:40 | #87 |
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Apple had a pretty tough time of it in the mid 90s too, no idea if they were on the brink. Was it the iMac and the iPod that turned it round for them?
It's probably useful to compare Apple's and Commodore's fates - niche computer makers squashed by the PC juggernaut on one side and Japanese consoles on the other. Is it that Apple cultivated a brand? It's not tech. or engineering that got Apple through but marketing. An earlier suggestion for the A500 / A600 to go downmarket is the only way I can see C surviving that, if they had carved themselves out a niche market as the cheap / first / bedroom computer. |
03 August 2018, 14:57 | #88 | |
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The suggestion was the exactly the thing Commodore should have made with the A1200, made it a cheap slim A500 instead (ditching CDTV, A500+, A600 and A1200 AGA) and held out for Hombre instead of rushing AGA into the market they already owned and in turn self combusting in on itself thanks to Commodore confusing the very consumers they were trying to sell to. Mac’s had the DTP market, PCs had the higher end mainstream computer gaming, the Amiga had the lower end computer market, there was no reason why the Amiga couldn’t have continued on this tangent. Even the budget console market was still selling Megadrives and Snes into 1998 even with the so called unstoppable PS1, thats the good thing about markets, there is more than one level. |
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03 August 2018, 15:13 | #89 | |
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Lisa is a special case and gets ~28MB/second - which means that AGA machines can access chip memory speed much faster than OCS & ECS but sadly only for the display. (and my point about bandwidth was that given the choice, I'd rather have seen a non-chunky Amiga with ~28MB/second Chip RAM bandwidth for all devices than a chunky one with ~7MB/second) The total bandwidth is shared, so any access done by either the chipset or the CPU potentially slows the other down (i.e. the A500 has about 7MB/second of bandwidth in total, of which the CPU can get about 3.5MB/second). Now follows the long version --------- I'll explain it for Chip RAM, because the answer for Fast RAM is "it all depends on what kind of Fast RAM". For Chip RAM, however, the results are known We need to know only a couple of things:
For all Amiga's, the speed of the chip memory bus is the same: about 3.54MHz (you might have heard it's 7MHz, but this is not actually true - a 7MHz memory bus@16 bits would allow for double the memory speed the Amiga actually has) For OCS Amiga's and all but one of the ECS Amiga's, the access width for both chipset and CPU is 16 bits For AGA Amiga's and the Amiga 3000, the access width from the perspective of the CPU is 32 bits For AGA Amiga's, the chipset accesses the bus as 16 bits wide - apart from Lisa, which accesses it as either 16, 32 or 64 bits wide In all these cases, the CPU is further limited in maximum bandwidth - it generally doesn't get more than 1/2 of the total slots the bus offers. Given these numbers, we can calculate the total Chip RAM bandwidth. Do note, however, that the bandwidth as seen by the CPU and as seen by the chipset can be different. The total available bandwidth doesn't change, but the ability to access it does. Code:
A500/A1000/A2000/A600 Total Chip RAM bandwidth = 3.54*16/8 = ~7MB/second Max CPU bandwidth = 3.54*16/8/2 = ~3.54MB/second* A3000 Total Chip RAM bandwidth = 3.54*16/8 = ~7MB/second Max CPU bandwidth = 3.54*32/8/2 = ~7MB/second** A1200/A4000/CD32 Total Chip RAM bandwidth (all except Lisa)= 3.54*16/8 = ~7MB/second Total Chip RAM bandwidth (Lisa only)= 3.54*64/8 = ~28MB/second*** Max CPU bandwidth = 3.54*32/8/2 = ~7MB/second** **) 32 bit Chip RAM access is limited to ~7MB/second instead of 14MB/second because 32 bit Chip RAM incurs a wait state (presumably from Agnus/Alice) ***) Lisa can access the Chip RAM in a more complicated way, which allows a quadrupling of standard bandwidth but requires the chip to fetch 64 bits every time I hope this helps. |
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03 August 2018, 15:45 | #90 | |
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In fact the situation seems simpler than that. The bus runs @3.5Mhz. However half the bus clocks are reserved for video output, regardless if they're used or not. Therefore at 16 bits we're limited to 3.5/2Mhz *2 bytes transfer speed, i.e. 3.5MB/s. And at 32 bits it's simply twice that amount. Of course Alice/Lisa can get all cycles and can do 7MB/s in 16 bits, 14MB/s in 32 bits, 28MB/s in 64 bits (actually double CAS). |
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03 August 2018, 15:45 | #91 | |
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03 August 2018, 17:17 | #92 | |
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In any case, the rest of my figures where at least correct |
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03 August 2018, 18:00 | #93 |
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Yup, anyway one sure thing is that chipmem is deadly slow. 50Mhz '030 has to wait ~28 clocks for a single access :/
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04 August 2018, 00:21 | #94 | |
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Yes, but all is not lost here, after writing into chip ram, the 68030 can continue executing code in parallell in fast ram, provided no more memory accesses are done during these 28 cycles. This means you can fetch data from memory into registers before doing the chip ram write and then continue calculating stuff in registers only after a chip write. This usually works rather well with a 68030, as some instructions are still rather slow, but a 68040/68060 starts to be too fast to use the idle time well, and there is a limit how much stuff you can read into unused registers before a chip write. |
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04 August 2018, 03:16 | #95 | |
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@roondar. Thanks for that long explanation it helped a lot.
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04 August 2018, 03:35 | #96 |
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04 August 2018, 09:27 | #97 |
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10 August 2018, 18:32 | #98 |
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Here is a nice an very detailed Blog about what it takes to speed up an Atari ST from 8MHz to 16MHz (and beyond) - not just the CPU but also access to the "ST RAM" (= our ChipRAM).
Very interesting as he tries many ways and documents not only success but also failure. It is not that easy ;-) The date is being clocked into the shifter at double speed, so the display simply runs out of data each scan line. Apart from that, the GLUE and MMU control the video syncs so they become unsuable also. The only way it could work is to re-build the video syncs, and build a new shifter than can take increased data input speeds, but still output at the correct speeds. Same would be true of course for the Amiga Custom Chips ... but I guess Commodore could have done that, if they would have realized early enough that the Amiga is a "computer platform" and not just a one-hit wonder... I think a real (switchable) 14MHz mode could/should be done by the time of ECS. |
10 August 2018, 19:08 | #99 | |
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16 August 2018, 17:05 | #100 |
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I think technology moved so fast throughout the 1990s that you needed to be able to rapid-fire release hardware upgrades to keep up. We went from 25MHz 386s and 68030s at the beginning of the decade to 1GHz Athlons chips at the end. Commodore never stood a chance.
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