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Old 04 October 2008, 00:27   #231
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Join Date: Jun 2008
Location: planet earth
Posts: 1,115
sorry, but feel the need for another *bump*:

Gunnar von Boehn:

The mainboard will have
a) 256MB Chipmem (64bit)
b) 256MB Fastmem (64bit)

The SuperAGA Chipset will use the Chipmem always as chipmem.
The 070 will use the Fastmem as Fastmem.

Each CPU card (PPC/Coldfire/or 68060) should have local fastmem on board. (Just like all the good AmigaTurbo card did have.)

Local memory on the CPU Card will of course have lower acess latency for the CPU than the fast memory on the mainbaord.

Because of this the Fast-memory bank be "turned" into chip-memory (with a switch) when you add a CPU-Card.

So if you have a CPU Card.
A good setup is to have whatever amount the CPU card has a fastmemory as fast memory and use the on board memory as 128bit wide, 512MB chipmemory.

If the CPU card has 2nd level cache.
- The PowerPC cards have 2nd level cache.
- The Coldfire V5 has 2nd level cache.
- And a 68060 card could be designed to have e.g. 1-2MB SRAM as 2nd level cache.

So if the card have 2nd level cache then the latency to the main board memory is less of a factor.
With we selfmade the second level cache, as like on a 68060 card, then we can put the latency into account.
We could do things like speculative prefetching memory lines early ahead into the 2nd level cache. This would help a lot on hiding the latency.

A higher clocked 68060 with few MB of 2nd level would be very powerful compared to original classic 68k systems.

Of course when our 070 design develops as we hope it does then the systems does not need a CPU card at all.

Seperating the (optional) CPU from the Board has the advantage that the same board can be used for customer which want the baord with 070 or which prefer their board with 060. This will lower the cost of the system for everybody.

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