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The reason they didn’t do a full 640×480 was because they were focused on TV-compatible video hardware, not because an 8MHz 68000 couldn’t handle it. Even with

The reason they didn’t do a full 640×480 was because they were focused on TV-compatible video hardware, not because an 8MHz 68000 couldn’t handle it. Even without Commodore’s terrible corporate structure they would have had a rough time improving Amiga because they painted themselves into a corner with an expensive chipset that developers had to work with directly for good performance and that didn’t have a lot of room to grow in a compatible fashion—the first real revision to the Amiga was 1990’s A3000, the A500 was just a value-engineered A1000 while the A2000 was just an A1000 with internal slots. No real change for 5 years would have prevented market growth, even if corporate management had been at all competent. They would have had a lot more leeway to make more interesting systems faster without the crushing weight of compatibility engineering. Apple was incredibly smart on that front with Macintosh—and the early introduction of Mac XL helped ensure developers didn’t ignore the “don’t touch the hardware directly” directive, at least for business software. That made the Mac II possible in 1987, and by the A3000’s release in 1990 Apple had an entire line of full 32-bit workstations that ran virtually all Mac software without weird caveats. And Windows 3.0 was also in the mix at that point on 386 and better PC hardware…

bogantech 3y ago
> The reason they didn’t do a full 640×480 was because they were focused on TV-compatible video hardware, not because an 8MHz 68000 couldn’t handle it. The interleaved memory access of the CPU & Agnus means that the amount of data that can be pulled from the RAM is directly related to the bus speed. This, combined with the horizontal line frequency and the bus width determines how many memory accesses there can be per line - to get a 640x480 progressive scan you'd have to double the amount of accesses per second and there's not enough access slots to do this at 7 MHz. When A1200 came out (too little too late by the end of '92) with AGA the CPU speed was doubled to 14MHz with a 32-bit wide bus which finally allowed for higher resolution progressive modes, more colours etc.
- eschaton 3y ago
  Or you dual-port the VRAM. Or you have a division between RAM banks managed by the OS, e.g. “slow” and “fast.” Or you have the custom chips mediate access to the VRAM entirely, but offer a DMA feature for, say, block transfers of bits. Or… There are lots of ways to support a full 640×480—or more—with an 8MHz 68000. Sun, Apollo, and HP all supported at least 1024×768 on their 68000/68010 workstations.
_the_inflator 3y ago
I agree. What seemed to be a game changer at the time and maybe was for a short period, the blitter and the bitmap concept, showed later on to be more of a burden than an asset.
bcrl 3y ago
The A3000 wasn't really much of a revision. True, it had a hack that made it possible for the CPU to access chip memory 32 bits at a time, but the chipset remained using a 16 bit data bus for all accesses. When running in the 640 pixel wide hires graphics mode using 4 bits per pixel, the memory bandwidth was completely saturated. The really sad part is that a motherboard the AGA chipset (which actually increased memory bandwidth for graphics, but not for the blitter and other parts of the chipset) was ready in an A3000 form factor about a year before the A4000 shipped. Heck, the A4000 couldn't ship in quantities to meet demand because Commodore was cash starved and couldn't afford to pay HP to make more chips. What a series of complete and total failures by management.
- eschaton 3y ago
  Yikes! So even the A3000 was hobbled by decisions made in 1983-85!

bogantech 3y ago

> The reason they didn’t do a full 640×480 was because they were focused on TV-compatible video hardware, not because an 8MHz 68000 couldn’t handle it. The interleaved memory access of the CPU & Agnus means that the amount of data that can be pulled from the RAM is directly related to the bus speed. This, combined with the horizontal line frequency and the bus width determines how many memory accesses there can be per line - to get a 640x480 progressive scan you'd have to double the amount of accesses per second and there's not enough access slots to do this at 7 MHz. When A1200 came out (too little too late by the end of '92) with AGA the CPU speed was doubled to 14MHz with a 32-bit wide bus which finally allowed for higher resolution progressive modes, more colours etc.

eschaton 3y ago
Or you dual-port the VRAM. Or you have a division between RAM banks managed by the OS, e.g. “slow” and “fast.” Or you have the custom chips mediate access to the VRAM entirely, but offer a DMA feature for, say, block transfers of bits. Or… There are lots of ways to support a full 640×480—or more—with an 8MHz 68000. Sun, Apollo, and HP all supported at least 1024×768 on their 68000/68010 workstations.

_the_inflator 3y ago

I agree. What seemed to be a game changer at the time and maybe was for a short period, the blitter and the bitmap concept, showed later on to be more of a burden than an asset.

bcrl 3y ago

The A3000 wasn't really much of a revision. True, it had a hack that made it possible for the CPU to access chip memory 32 bits at a time, but the chipset remained using a 16 bit data bus for all accesses. When running in the 640 pixel wide hires graphics mode using 4 bits per pixel, the memory bandwidth was completely saturated. The really sad part is that a motherboard the AGA chipset (which actually increased memory bandwidth for graphics, but not for the blitter and other parts of the chipset) was ready in an A3000 form factor about a year before the A4000 shipped. Heck, the A4000 couldn't ship in quantities to meet demand because Commodore was cash starved and couldn't afford to pay HP to make more chips. What a series of complete and total failures by management.

eschaton 3y ago
Yikes! So even the A3000 was hobbled by decisions made in 1983-85!