Spain, April 23th 2000
Hello to everybody.
I will tell some things about Z380 in a fast way.
1- As I own one Z380 card, I know what I am talking about.
2- About a FlashRom for Z380 BIOS: It is dangerous !! If you program the
BIOS and make a bug, maybe the Z380 will never run again because the bug.
So, how can you correct the bug if you cannot use Z380 to re-program the
FlashRom ??
It is like PC FlashRom Bios trouble, and famous VIRUSES. The virus delete
the BIOS memory, and you must waste the main board !!
Well, you can use a removable FlashRom chip, but I don't know if it is easy.
Anyway, it will increase the price of the board, and can allow some non
compatibility if people reprogram the BIOS by his way.
3- About the comparisons from Z180 to Z380, I heard a lot of incorrect
things from Z380. Please, read the Z380 information from Zilog's web
www.zilog.com ) Documents are in PDF format.
The Z380 seems to be the definitive Zilog's processor. It is fully 32 bits
processor, and the instruction set is very proper, as it includes a lot of
new instructions, addressing modes, and so.
You can make 32 bits loads, operations and comparisons, even without using
DDIR commands (because you can turn from 16 bit mode to 32 bit mode with
only one command)
The memory is fully linear ( 4 GB of addressing space )
4- I think that the Z380 solves the MSX CPU limitations.
The best feature, is the linear memory (32 bits to access it) because it
allows to make long programs that deal with long data segments. Now, you
don't need to map the memory like the Z80, using the memory map.
At the same CPU speed, Z380 is double fast than Z80 executing the same
instructions.
This Z380 card is 14.3 MHz, so, it is similar to a Z80 at 28.6 MHz.
And if you use 32 bits registers, you do the same things with half
instructions.
5- New instructions: The MULT and DIV instructions are always useful, but
they are used very few times. Anyway, you have them.
But the more interesting instructions, are the ones like 32 bits transfer,
relative jumping ( CALLR, JR with 8,16,24 bits of relative address)
Also, the 8 sets of registers (HL,DE,BC,AF,IX,IY) that allows you to make
faster routines avoiding so much memory access.
At the 16 bits memory mode, you can make faster data loads...
I think that the Z380 instruction set is perfect to MSX.
The only thing is that by now, the speed of 14.3 MHz is the only way of
having a mid-prize board, but it is enough for MSX.
6- Other thing: The "BOTH" mode of using the LPE-Z380 card: It doesn't turn
off the main MSX processor: That is, you use the Z80+Z380 or R800+Z380 at
the same time.
As the Z380 needs the MSX CPU to manage with internal I/O data, memory, DISK
Rom, and so, it is a very special way of working:
-The main program can run on the Z380
-The MSX CPU works as Hardware sever ( ports, MSX memory, Roms like diskrom,
keyboard, VDP, Vram, ...)
So, it is a paralell working mode, in wich you add the both processor's
power.
This way, you can use the MSX hardware (like VRAM) at 100% because the Z80
is 100% transferring data.
If you use only 1 processor at the system, you will not use VRAM at 100%
because the processor also must run the whole program.
Well, that's all by now.
Bye.
Daniel Zorita [EMAIL PROTECTED]
****
MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED]
and put "unsubscribe msx [EMAIL PROTECTED]" (without the quotes) in
the body (not the subject) of the message.
Problems? contact [EMAIL PROTECTED]
More information on MSX can be found in the following places:
The MSX faq: http://www.faq.msxnet.org/
The MSX newsgroup: comp.sys.msx
The MSX IRC channel: #MSX on Undernet
****
