7 ms·

I wonder how much faster the ARM2 would have been compared to the 68k in a first-generation Amiga. The Amiga's chip memory only delivered 7 MBytes/s, shared bet

by tralarpa 11mo ago

I wonder how much faster the ARM2 would have been compared to the 68k in a first-generation Amiga. The Amiga's chip memory only delivered 7 MBytes/s, shared between the CPU and the chipset! With its 32-bit instruction words, the ARM2 would have been very far from its theoretical performance.

memsom 11mo ago
Well - I used Archimedes computers with ARM2 and owned an Amiga 500+ and honestly, I couldn't tell you the Arcie was faster. It certainly didn't have the custom chips, so it is probably not a fair comparison.
lproven 11mo ago
> I wonder how much faster the ARM2 would have been compared to the 68k in a first-generation Amiga. Considerably faster. I looked at both (and the ST) and bought an Archimedes. ARM chips benchmarked from the ARM2 up to the RasPi 3B+: https://stardot.org.uk/forums/viewtopic.php?t=20379 https://stardot.org.uk/forums/viewtopic.php?t=20379 68000 benchmarks around that time: http://www.faqs.org/faqs/motorola/68k-chips-faq/ http://www.faqs.org/faqs/motorola/68k-chips-faq/ ARM2: Dhrystone/sec 5463 68000 @ 8MHz: Dhrystones 68000 2100 MIPS https://en.wikichip.org/wiki/acorn/microarchitectures/arm2 https://en.wikichip.org/wiki/acorn/microarchitectures/arm2 https://en.wikipedia.org/wiki/Instructions_per_second https://en.wikipedia.org/wiki/Instructions_per_second ARM2: from 6 to 10 million instructions per second, depending on instruction mix 68000: 1.4 MIPS typical. (For comparison: Intel 8086 at the same speed, something like 300 Whetstones, 0.5 MIPS. So either of them stomped all over a comparable x86 machine from that time.) So, very roughly, ARM2 was between 2-3x faster in typical use. Note: . Neither CPU could do FP in hardware. . Neither had cache memory. . The Amiga had a lot of complex hardware acceleration for graphics; the original ARM2 machines from Acorn (Archimedes A2305, A310, A400) had essentially none. So, Amiga games could do things that on the Arc required raw CPU, typically done careful hand-coded assembler.
- tralarpa 11mo ago
  Yes, but that's my point: the ARM2 cannot get faster than 1.25 MIPS in an Amiga because of the memory bandwidth (assuming that the CPU uses 5 MBytes/s of the available 7 MBytes/s that it has to share with the graphics chipset).
  - actionfromafar 11mo ago
    To this day my pet peeve is that Commodore didn't ship Amigas with a tiny amount of scratch RAM independent of the shared bus. Would have been so useful.
    - lproven 11mo ago
      Is that not the distinction between Chip RAM and Fast RAM in real machines? https://en.wikipedia.org/wiki/Amiga_Chip_RAM https://en.wikipedia.org/wiki/Amiga_Chip_RAM
      - rasz 11mo ago
        Afaik only A3000 and A4000 shipped with Fast ram, both computers werent really price competitive with PCs.
      - actionfromafar 11mo ago
        A large amount of Fast Ram would have been even more useful, but if you are cost optimizing the BOM, just a tiny sliver of it (it being Fast RAM) would have been effectively a "manual cache" managed by the developer and would have been incredibly useful for anything computation intense, like flight simulators, spreadsheets, anything not involving just blitting graphics really.
        rasz 11mo ago
        And it wouldnt even be that hard, just two 2kx8 SRAMs (like the ones in every NES/Famicon) and CS line going from the chipset to map it somewhere high outside the range of the chipset was very logical, easily doable in 1987 and most importantly cheap. Those 6116 srams were below $2 retail in 1987 (Byte magazine retail prices), so $4 for big performance boost. Hell, smart Commodore would design A500 with second trapdoor near the CPU. Ship unpopulated but offer official Commodore "turbo ram" expansion carts: - $25 4KB version. $8 BOM, 2x $1.95 6116 - $40 8KB. $12 BOM, 2x $3.5 6264 - $100 64KB. $28 BOM, 2x $12 62256 - Extreme $400 256KB. $120 BOM, 8x $12 62256. Would stick out due to big PCB so make it an attractive piece of plastic with cool logo and "EXTREME" design. Map it at D80000 (potential 256KB of space for activities) and let software vendors auto detect fitted option by running quick memory test. Easy speed boost and easy extra money for Commodore.

memsom 11mo ago

Well - I used Archimedes computers with ARM2 and owned an Amiga 500+ and honestly, I couldn't tell you the Arcie was faster. It certainly didn't have the custom chips, so it is probably not a fair comparison.

lproven 11mo ago

> I wonder how much faster the ARM2 would have been compared to the 68k in a first-generation Amiga. Considerably faster. I looked at both (and the ST) and bought an Archimedes. ARM chips benchmarked from the ARM2 up to the RasPi 3B+: https://stardot.org.uk/forums/viewtopic.php?t=20379 https://stardot.org.uk/forums/viewtopic.php?t=20379 68000 benchmarks around that time: http://www.faqs.org/faqs/motorola/68k-chips-faq/ http://www.faqs.org/faqs/motorola/68k-chips-faq/ ARM2: Dhrystone/sec 5463 68000 @ 8MHz: Dhrystones 68000 2100 MIPS https://en.wikichip.org/wiki/acorn/microarchitectures/arm2 https://en.wikichip.org/wiki/acorn/microarchitectures/arm2 https://en.wikipedia.org/wiki/Instructions_per_second https://en.wikipedia.org/wiki/Instructions_per_second ARM2: from 6 to 10 million instructions per second, depending on instruction mix 68000: 1.4 MIPS typical. (For comparison: Intel 8086 at the same speed, something like 300 Whetstones, 0.5 MIPS. So either of them stomped all over a comparable x86 machine from that time.) So, very roughly, ARM2 was between 2-3x faster in typical use. Note: . Neither CPU could do FP in hardware. . Neither had cache memory. . The Amiga had a lot of complex hardware acceleration for graphics; the original ARM2 machines from Acorn (Archimedes A2305, A310, A400) had essentially none. So, Amiga games could do things that on the Arc required raw CPU, typically done careful hand-coded assembler.

tralarpa 11mo ago
Yes, but that's my point: the ARM2 cannot get faster than 1.25 MIPS in an Amiga because of the memory bandwidth (assuming that the CPU uses 5 MBytes/s of the available 7 MBytes/s that it has to share with the graphics chipset).
- actionfromafar 11mo ago
  To this day my pet peeve is that Commodore didn't ship Amigas with a tiny amount of scratch RAM independent of the shared bus. Would have been so useful.
  - lproven 11mo ago
    Is that not the distinction between Chip RAM and Fast RAM in real machines? https://en.wikipedia.org/wiki/Amiga_Chip_RAM https://en.wikipedia.org/wiki/Amiga_Chip_RAM
    - rasz 11mo ago
      Afaik only A3000 and A4000 shipped with Fast ram, both computers werent really price competitive with PCs.
    - actionfromafar 11mo ago
      A large amount of Fast Ram would have been even more useful, but if you are cost optimizing the BOM, just a tiny sliver of it (it being Fast RAM) would have been effectively a "manual cache" managed by the developer and would have been incredibly useful for anything computation intense, like flight simulators, spreadsheets, anything not involving just blitting graphics really.
      - rasz 11mo ago
        And it wouldnt even be that hard, just two 2kx8 SRAMs (like the ones in every NES/Famicon) and CS line going from the chipset to map it somewhere high outside the range of the chipset was very logical, easily doable in 1987 and most importantly cheap. Those 6116 srams were below $2 retail in 1987 (Byte magazine retail prices), so $4 for big performance boost. Hell, smart Commodore would design A500 with second trapdoor near the CPU. Ship unpopulated but offer official Commodore "turbo ram" expansion carts: - $25 4KB version. $8 BOM, 2x $1.95 6116 - $40 8KB. $12 BOM, 2x $3.5 6264 - $100 64KB. $28 BOM, 2x $12 62256 - Extreme $400 256KB. $120 BOM, 8x $12 62256. Would stick out due to big PCB so make it an attractive piece of plastic with cool logo and "EXTREME" design. Map it at D80000 (potential 256KB of space for activities) and let software vendors auto detect fitted option by running quick memory test. Easy speed boost and easy extra money for Commodore.