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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: utri007 on January 18, 2020, 11:30:02 AM
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I have TerribleFire 520 accelerator wich has 68020 cpu, and it has no RAM it's own. Fast RAM is in GVP HD8+ ram & SCSI board.
This way it is a 1,68x faster than original A500.
OK, I can really understand this, BUT
I had a Supra turbo with very similar setup. I doesn't have RAM it is own and it uses external fast ram on side connector.
It was 5,89x faster than A500
How did Supra turbo was so much faster? Could 16kb cache explain this?
http://amiga.resource.cx/exp/supra28
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I have no idea of the clock frequency on your TF520, but the Supra seems to have 35MHz, which is a lot.
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It is 37mhz
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Care to share a screenshot of the Sysinfo report on TF520?
Does it have Cache option switched on?
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Here
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This is odd, certainly. It should be on-par with an A1200, at least.
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I know that there are performance problems with accelerators like this. But I wonder what makes difference between this and Supra accelerator? Can it really be that 16kb data cache wich supra has?
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Yes, cache is good. But Your Sysinfo screenshot doesn't make sense at all. It clearly recognizes the clock speed but still missed out Mips and Dhrystones. Even without Fast RAM it should be twice as fast as an A1200/14MHz.
Almost like running with handbrake. Is it configurable, jumpers maybe?
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it should be twice as fast as an A1200/14MHz.
A1200 has a 32-bit bus at least, this doesn't. Since '020 always wants to read 32 bits at a time, that means two bus cycles in a row. The waits will pile up badly.
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But the Supra has only a 68HC000, which is also not 32bit, afaik.
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Cache is effectively fastram wired directly to the CPU. They can work both as fast as each other.
If you have sidecar fastram and a cpu socket turbo board, the cpu must talk to the fastram through the Amiga500 bus, which is working at a much slower speed. So performance chokes.
It's like if you have 10 lane 70mph highway and then make it all go over a one-lane stone arch bridge with traffic lights. Big bottleneck.
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Cache is effectively fastram wired directly to the CPU. They can work both as fast as each other.
If you have sidecar fastram and a cpu socket turbo board, the cpu must talk to the fastram through the Amiga500 bus, which is working at a much slower speed. So performance chokes.
It's like if you have 10 lane 70mph highway and then make it all go over a one-lane stone arch bridge with traffic lights. Big bottleneck.
I know, but why Supra is that much faster? I t doesn't have ram, ram is in sidecar and CPU is 68000, biggest difference to Terrible Fire 520 is tiny 16kb data cache.
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Cache is effectively fastram wired directly to the CPU. They can work both as fast as each other.
If you have sidecar fastram and a cpu socket turbo board, the cpu must talk to the fastram through the Amiga500 bus, which is working at a much slower speed. So performance chokes.
It's like if you have 10 lane 70mph highway and then make it all go over a one-lane stone arch bridge with traffic lights. Big bottleneck.
I know, but why Supra is that much faster? I t doesn't have ram, ram is in sidecar and CPU is 68000, biggest difference to Terrible Fire 520 is tiny 16kb data cache.
Does the Supra feel that much faster though in real life use?
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I know, but why Supra is that much faster? I t doesn't have ram, ram is in sidecar and CPU is 68000, biggest difference to Terrible Fire 520 is tiny 16kb data cache.
I literally just told you why, right in the very first sentence.
Cache is ram. More importantly, it is ram which is directly connected to the CPU, there's no motherboard bus bottleneck between the two.
So obviously performance is better because it has direct access to 16kb of high speed ram here. 16kb is a very respectable size cache for a late 80s system.
This is the whole point of cache. Every system where CPU's access to main ram is slow uses cache for this. Including your modern day PC.
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Yes you did. Sorry. Cache seems to make huge difference even if ram is in side car. Wich is somewhat weird.
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This makes the TF520 almost useless, imho. Why burn this card with 35MHz for a Result of 20% against an A500/A2000?
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TF520 makes A500 1,7x faster than it originally was. Price is also very low, so it is very nice card for a price.
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Yes you did. Sorry. Cache seems to make huge difference even if ram is in side car. Wich is somewhat weird.
it's not weird at all.
every time your 020 board communicates with sidecar ram, it must do so over the Amiga 500 motherboard CPU bus, which is working only at the speed a 7mhz 68000 expects.
You can have a 200mph Ferrari, but if the speed limit on the road is 20mph, you won't get to the supermarket any faster than a lada.
Cache is a private race track for your Ferrari, you can go as fast as you want there.
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This makes the TF520 almost useless, imho. Why burn this card with 35MHz for a Result of 20% against an A500/A2000?
It's not useless, it's a step in the direction of even better cards. That is one of the great things with the TerribleFire series of cards, they evolve over time, become better and better, yet every card is very affordable, so upgrading every now and then does not cost a small fortune. And you can reuse parts, lowering the cost even further.
It was a different story when I bought the Phase5 Blizzard 1230 III right before the 1230 IV came, back in 1994... :p