I wrote a detailed description of R800 for the Wikipedia, most of this information I gathered while making some projects using VHDL and FPGA. I hope you enjoy the info.

Nice!

Just one note... RISC is not a fixed set of characteristics a CPU should have. In essense, the R800 is designed upon many RISC ideas, and thus has the right to call itself RISC.

One of the most popular RISC CPU's, the ARM, also has complex addressing modes and does not resemble the 'typical' RISC CPU.

So the R800 is a RISC processor running a CISC instruction set.

Also note, CISC does not really exist as a term. It just means 'everything not RISC'.

Also note, the Z80 architecture /is/ mainly load-store, and looks much more RISC than, say a 68000 or 80x86 does.

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In essense, the R800 is designed upon many RISC ideas, and thus has the right to call itself RISC.

Every modern processor is RISC if you look at it that way. My pc has a Intel Pentium 4 RISC CPU!

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So the R800 is a RISC processor running a CISC instruction set.

No, the R800 is a CISC processor.
RISC involves two things: implementation and, more important, architecture. The Z80 (and thus the R800) architecture has nothing to do with RISC...

Troll alert!

Sjoerd, don't you have something better to do than trying to pick fights?

Everybody with some knowledge of CPU's knows a Pentium 4 is in fact a RISC processor with a x86 translation layer on top of it.

After some mature conversation on IRC, you seem bent on trying to pick fights with me. Two in one night!

I should know better than to reply to this, but no moderators seem to be around today... From now on, I will take the following to heart:

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                          /|  /|  |                          |
                          ||__||  |       Please don't       |
                         /   O O\__           feed           |
                        /          \       the trolls        |
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                     /    |\____\     \     ||
                    /     | | | |\____/     ||
                   /       \|_|_|/   |    __||
                  /  /  \            |____| ||
                 /   |   | /|        |      --|
                 |   |   |//         |____  --|
          * _    |  |_|_|_|          |     \-/
       *-- _--\ _ \     //           |
         /  _     \\ _ //   |        /
       *  /   \_ /- | -     |       |
         *      ___ c_c_c_C/ \C_c_c_c____________

Thank you, Ricardo! Great entry, very informative. I like the fact that it's true to facts and doesn't try to represent R800 as something it is not.

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Each 30us, the CPU is halted for 4us, this time is used to refresh a block of the RAM.

Does that mean that the R800 spends 12% of its CPU time on refreshing the RAM? Is this figure really that high? I always figured it to be lower...

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Everybody with some knowledge of CPU's knows a Pentium 4 is in fact a RISC processor with a x86 translation layer on top of it.

Yes, translated to RISC-ops, right? That's what Intel wants you to think, because somehow it sounds better. It's called marketing. Pentium == CISC. Try google 'risc vs cisc' or something.

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After some mature conversation on IRC, you seem bent on trying to pick fights with me. Two in one night!

Well, don't take it personally. Everybody who says R800 is RISC can get this reaction. Because it is not. That has nothing to do with you. I even thought of editing my reaction here, but I was already too late. OTOH it would be kinda stupid to not react just because it's you.

{mod:bart}

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I should know better than to reply to this

. You should listen to yourself some more. The fact that you feel lured into a fight doesn't make up for swearing and personal insults.
{/mod:bart}

The RISC Wikipage clearly confirms what I said.

We'll talk again when you get a clue!

Take a scale, write RISC on one side, and CISC on the other side. Put all the things that are RISC-y in the R800 on the RISC side, and all the things that are CISC-y on the CISC side. It WILL tip over to the RISC side. Again, it's very much like ARM, which has a lot of CISC features.

R800 is a RISC implementation of the Z80 achitecture, and that's final!

Well every smart person can say That The R800 is a risc Processor

The r800 the little brother from the R8000 (used in the silicon grafix machines)

and the R stands for Risc

since when do you spell Cisc with an R from R800

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Does that mean that the R800 spends 12% of its CPU time on refreshing the RAM? Is this figure really that high? I always figured it to be lower...

Well, the Z80 spends a lot more time on refresh!
It's just a bit of a bummer the R800 is halted some periods.. It could affect line interrupts and such...

sadly al the stuf around the r800 is working slower than the r800 it self thats why the r800 has to wait a Lot.

Removed some off topic forumpostings. From now on, only on topic, please!

There are a lot of removings lately...

Oh, I almost forgot! The R800 is a RISC processor!

http://rds.yahoo.com/S=2766679/K=R800+RISC/v=2/SID=e/TID=DFXH_2/l=WS5/R=2/*-http://216.109.117.135/search/cache?p=R800+RISC&ei=UTF-8&cop=mss&u=en.wikipedia.org/wiki/R800&w=r800+risc&d=E10D41D841&icp=1&.intl=us

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Oh, I almost forgot! The R800 is a RISC processor!

No, the R800 is a CISC processor.
RISC involves two things: implementation and, more important, architecture. The Z80 (and thus the R800) architecture has nothing to do with RISC...

There.