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AuthorTopic: What are the real speeds of Zorro II and III ?  (Read 1342 times)

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What are the real speeds of Zorro II and III ?
« on: April 29, 2007, 03:32:35 AM »
In another thread, I saw somebody say that the transfer speed of the Zorro II slots is 7 MByte/S (perhaps 7.14 MB/S considering the clock) and that the transfer speed of the Zorro III slot is 25MByte/s.

Something doesn't make sense here.

If the Zorro II slot operates at 7.16 MHz and it is a 16 bit bus (16bit = 2 byte) then its transfer speed should really be 14.32 MByte/s. And if the Zorro III bus operates at 25MHz and it is a 32 bit bus (32bit = 4 byte) then its real transfer speed should be 100 MByte/s.

Does anybody know the truth about the maximum realistic (not the theoretical unachievable speeds...) transfer speeds of these busses ?
 

Offline Piru

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Re: What are the real speeds of Zorro II and III ?
« Reply #1 on: April 29, 2007, 03:53:42 AM »
Quote
In another thread

Which thread?

The figures quoted are totally wrong.

Anyhow, Zorro II maximum speed is about 3.58MB/s. Zorro III theoretical maximum is 50MB/s, but (afaik) chipset limitations put the real life maximum performance to about 25MB/s. Typical real life performance is somewhere around ~20MB/s.

Here's some more, and here.
 

Offline LoadWB

Re: What are the real speeds of Zorro II and III ?
« Reply #2 on: April 29, 2007, 05:32:52 AM »
I looked up "cool" and quite literally found a picture of Dave Haynie.


I'm curious... why not a Zorro III card with an SDRAM slot supporting 512MB or 1GB?
 

  • Guest
Re: What are the real speeds of Zorro II and III ?
« Reply #3 on: April 29, 2007, 05:55:43 AM »
@Piru

Thanks, and nice links too!

The speeds of Zorro III seems very similar to VESA Local Bus speeds popularized after EISA.
 

Offline alexh

Re: What are the real speeds of Zorro II and III ?
« Reply #4 on: April 29, 2007, 09:55:35 AM »
Quote
If the Zorro II slot operates at 7.16 MHz and it is a 16 bit bus (16bit = 2 byte) then its transfer speed should really be 14.32 MByte/s.

That would be true if only there were not four clocks per bus cycle (Amiga Hardware Reference Manual, Page 391). There doesnt seem to be a burst mode and so 1 bus cycle is 16-bits. This is where the 3.58Mbyte/s value that is quoted in lots of places comes from.

(Note that Zorro II is a CPU clock synchronous bus and so PAL systems are 7.09MHz or 3.54Mbyte/s)

Quote
And if the Zorro III bus operates at 25MHz and it is a 32 bit bus (32bit = 4 byte) then its real transfer speed should be 100 MByte/s.

Zorro III is a totally asynchronous bus and so "25MHz*32-bit" is meaningless. The maximum speed of the Zorro III bus is determined by the setup-and-hold times of strobe signals going to the BUSTER. These are discussed in the HRM but I am not going to quote/prove them here.
 

Offline Iggy_Drougge

Re: What are the real speeds of Zorro II and III ?
« Reply #5 on: May 07, 2007, 02:22:25 AM »
Quote

LoadWB wrote:
I'm curious... why not a Zorro III card with an SDRAM slot supporting 512MB or 1GB?

Zorro III memory is extremely slow; ask anyone who owns a DKB 3128 or Fastlane Z3.
A4000/25MHz/64MB/20GB/RetinaBLTZ3/FastlaneZ3/CatweaselMKIII/Ariadne/A2301
A3000/40MHz/32MB/6GB/Merlin/Buddha/X-Surf/FrameMachineII+Prism24
Draco60/50MHz/128MB/15GB/Altais/DracoMotion/DV/IOblix+net
 

Offline Vincent

Re: What are the real speeds of Zorro II and III ?
« Reply #6 on: May 07, 2007, 03:07:42 PM »
Quote

Iggy_Drougge wrote:
Zorro III memory is extremely slow; ask anyone who owns a DKB 3128 or Fastlane Z3.

So it's fastlane during rush hour then ;-)
Xbox360
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I don\'t think I have the stomach for it." - Raziel
 

Offline mboehmer_e3b

Re: What are the real speeds of Zorro II and III ?
« Reply #7 on: May 07, 2007, 04:24:24 PM »
Quote
... but (afaik) chipset limitations put the real life maximum performance to about 25MB/s. Typical real life performance is somewhere around ~20MB/s.


For 20MB/s you will need to break some timings, especially on the /DTACK signal to get fast. This may work with many CPU card, or not. Write accesses are no problem with today's logic, but reads are, especially if you go for synchronous designs (see below).

I would not expect more than 15MB/s from a real life Zorro III card. With old chipsets and logic you can reliably do asynchronous designs, yielding in high speed (and the danger of spikes, too).

With modern high speed logic and I/O chips you will have to go for synchronous designs. Simply as new chips will accept even small spikes as /RD or /WR signals, so you will need quite some amount of synchronization logic (which Dave Haynie did mention already in the BigRAM documentation - "metastability").

Which means that synchronisation will cost extra time, but this can't be avoided if you want a stable system.

Next problem is that almost no CPU card (> 030 CPU) does support burst accesses on Zorro III. I have seen only 030 CPUs doing burst accesses up to now on Zorro III.
So you can't utilize the Zorro III burst mode which may give you extra performance.

Michael

 

Offline Piru

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Re: What are the real speeds of Zorro II and III ?
« Reply #8 on: May 07, 2007, 04:26:49 PM »
Eow, that's quite sucky.
 

Offline Karlos

Re: What are the real speeds of Zorro II and III ?
« Reply #9 on: May 07, 2007, 05:47:17 PM »
Are there any buses on classic systems that aren't woefully slow?

I remember getting a bit excited when I first fitted my BVision card, thinking "Well, it's got a local mini-pci connection to the Blizzard, I bet that should outperform a lot of the bix box amiga rivals for raw transfer speed".

Poor naive fool I was ;-) It gets about 16MB/s write speed using move16 on the 040 and about 18MB/s on the PPC (using 64-bit FPU register based transfers).

No where near fast enough for decent video streaming, or to max out the GPU with basic polygon rendering requests. Like just about every piece of hardware for any classic system, let down by dire bus performance.

Still, at least it's a bit faster than the mediator in that regard...
int p; // A
 

Offline adolescent

Re: What are the real speeds of Zorro II and III ?
« Reply #10 on: May 07, 2007, 07:19:04 PM »
@Karlos

Are you ever going to compile and post your bus test benchmarks?  (Or, have you?)

Time to move on.  Bye Amiga.org.  :(