Accelerator without ram performance.

[utri007]

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

[TribbleSmasher]

I have no idea of the clock frequency on your TF520, but the Supra seems to have 35MHz, which is a lot.

[utri007]

It is 37mhz

[TribbleSmasher]

Care to share a screenshot of the Sysinfo report on TF520?
Does it have Cache option switched on?

[utri007]

Here

[TribbleSmasher]

This is odd, certainly. It should be on-par with an A1200, at least.

[utri007]

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?

[TribbleSmasher]

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?

[DamageX]

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.

[TribbleSmasher]

But the Supra has only a 68HC000, which is also not 32bit, afaik.

[CBH]

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.

[utri007]

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.

[paul1981]

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?

[CBH]

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.

[utri007]

Yes you did. Sorry. Cache seems to make huge difference even if ram is in side car. Wich is somewhat weird.