Can eZ80 speed up MSX?

Can eZ80 speed up MSX?

Post by Pierre Giel » Fri, 24 Sep 1999 04:00:00



eZ80: easy and simply 4 times faster?

I've looked at the documentation of Zilogs new CPU, the eZ80 and think
it is interesting. Even without changing the clock speed, it should be
4 times faster than a standard Z80, which would mean a virtual 14,3
MHz on a standard MSX and even 28,6MHz on a 7MHz machine. The CPU
could run at higher clock speeds (up to 80MHz) but that would require
major changes in the rest of the MSX-hardware.

So, does anybody know if it would be possible to just pull out the old
Z80A (or in some cases the Z80H) and replace it with the eZ80 (on a
little printed circuit board to make it fit in a DIL-socket) ??? I'm
not all that familiar with hardware and the Zilog site doesn't clarify
if you can do that.

Of course, in this case you wouldn't use the advanced posibilities of
the eZ80, like directly addressing 64MB of RAM and using the internal
TCP/IP stack which makes it easy to connect to the Internet. But at
least it would be simple and 100% compatible.

Any ideas, someone?

Pierre

 
 
 

Can eZ80 speed up MSX?

Post by Sander Zuidem » Fri, 24 Sep 1999 04:00:00


I guess it's interesting too, but

- No MMU (I thought)
- In what speeds other than 80Mhz will the chip be available, for 80Mhz is
(I think) WAY too much for our poor VDP


Quote:> eZ80: easy and simply 4 times faster?

> I've looked at the documentation of Zilogs new CPU, the eZ80 and think
> it is interesting. Even without changing the clock speed, it should be
> 4 times faster than a standard Z80, which would mean a virtual 14,3
> MHz on a standard MSX and even 28,6MHz on a 7MHz machine. The CPU
> could run at higher clock speeds (up to 80MHz) but that would require
> major changes in the rest of the MSX-hardware.

> So, does anybody know if it would be possible to just pull out the old
> Z80A (or in some cases the Z80H) and replace it with the eZ80 (on a
> little printed circuit board to make it fit in a DIL-socket) ??? I'm
> not all that familiar with hardware and the Zilog site doesn't clarify
> if you can do that.

> Of course, in this case you wouldn't use the advanced posibilities of
> the eZ80, like directly addressing 64MB of RAM and using the internal
> TCP/IP stack which makes it easy to connect to the Internet. But at
> least it would be simple and 100% compatible.

> Any ideas, someone?

> Pierre


 
 
 

Can eZ80 speed up MSX?

Post by Pierre Giel » Fri, 24 Sep 1999 04:00:00


On Thu, 23 Sep 1999 16:05:34 +0200, "Sander Zuidema"


>- No MMU (I thought)

The eZ80 can run in native Z80 mode (64kB). The MMU is not enabled
then.

Quote:>- In what speeds other than 80Mhz will the chip be available, for 80Mhz is
>(I think) WAY too much for our poor VDP

It should be able to run at lower speeds. The information on the Zilog
website just states that it can run at a speed of *up to* 80MHz. And
that the eZ80 is 4 times faster than a Z80 at the same clock speed.
That alone would already make it interesting to a lot of MSX users.

Pierre

 
 
 

Can eZ80 speed up MSX?

Post by Pierre Giel » Fri, 24 Sep 1999 04:00:00


So I got impatient... I've mailed this question to Zilogs customer
support:

Dear Sirs,

The specifications of the new eZ80 CPU are impressive. I've read in
the description that it will operate 4 times faster than a Z80 at the
same clock speed, which makes me wonder if I can simply replace a Z80
with an eZ80 without having to change the rest of the hardware design?
Would it be possible to just pull out the old Z80A and replace it with
the eZ80 on a little printed circuit board to make it fit in a
DIL-socket?

Sincerely,
Pierre Gielen

Now once more, I'm impatiently waiting for an answer...

 
 
 

Can eZ80 speed up MSX?

Post by Denni » Fri, 24 Sep 1999 04:00:00


Now once more, I'm impatiently waiting for an answer...

So ame I please keep share your mail's from zilog with this NG.

Dennis

 
 
 

Can eZ80 speed up MSX?

Post by G.S. Vigneau » Sat, 25 Sep 1999 04:00:00




Quote:>eZ80: easy and simply 4 times faster?

>I've looked at the documentation of Zilogs new CPU, the eZ80 and think
>it is interesting. Even without changing the clock speed, it should be
>4 times faster than a standard Z80, which would mean a virtual 14,3
>MHz on a standard MSX and even 28,6MHz on a 7MHz machine. The CPU
>could run at higher clock speeds (up to 80MHz) but that would require
>major changes in the rest of the MSX-hardware.

>So, does anybody know if it would be possible to just pull out the old
>Z80A (or in some cases the Z80H) and replace it with the eZ80 (on a
>little printed circuit board to make it fit in a DIL-socket) ??? I'm
>not all that familiar with hardware and the Zilog site doesn't clarify
>if you can do that.

>Of course, in this case you wouldn't use the advanced posibilities of
>the eZ80, like directly addressing 64MB of RAM and using the internal
>TCP/IP stack which makes it easy to connect to the Internet. But at
>least it would be simple and 100% compatible.

>Any ideas, someone?

>Pierre

Zilog may not want to commit themselves at this
early stage. The current Processor Description
document is too incomplete to offer conclusions.

Up to page 16 of the eZ80 Operational Description,
the answer seems to be "Yes".  But, at the bottom of
page 16, there is the following note:

  "The Z80 and Z80180 instruction sets include an
  RETI instruction that is used for servicing Z80
  peripherals. Because the eZ80 does not include
  these peripherals, nor does it allow them to be
  connected externally, there is no reason to ever
  conclude an eZ80 ISR with an RETI."

This is especially confusing, because earlier pages
discuss the IEI-IEO daisy-chain feature which is unique
to Z80 peripherals.

If the eZ80 runs 4 times faster than a Z80 at the same
clock frequency, there's a potential for problems with
memory i/o in an existing Z80 circuit -- particularly
with slower ROMs. And. timing loops may cause problems
with some i/o devices, such as floppy drives.

I think a bigger potential hassle with the eZ80 is the
mixed 16/24-bit architecture. Typical code that works in
Native Z80 mode will crash in ADL mode, and vice versa.

The eZ80 creates a new native data type: the 24-bit
integer, meaning that special compilers will need to be
written for it (the compiler makers will be delighted,
for the new business). How does the 24-bit integer work
within Zilog's little-endian world, where bytes/words
are stored in reverse order? For example, the following
two data lines are equivalent in a 16-bit little-endian
environment...

    dw  1234H                     ; int
    db  34H, 12H                  ; char, char

With long integers, these three lines are equivalent...

    dd  12345678H                 ; longint
    dw  5678H, 1234H              ; int, int
    db  78H, 56H, 34H, 12H        ; char, char, ...

Is this the 24-bit integer/register scenario?...

    dd  123456789ABCH                   ; longint
    dw  789ABCH, 123456H                ; int, int
    db  0BCH, 9AH, 78H, 56H, 34H, 12H   ; char, char, ...

The eZ80 programming model is also awkward: The
"Virtual Z80" mode is said to offer multiple Z80
tasks their own partitions -- but "interrupts and
trap locations are never mapped." This means that
*all* tasks must share common interrupt service
routines, located in the first 64k of memory.

Greg Vigneault

http://home.korax.net/~telic
September 24, 1999, Toronto.

 
 
 

Can eZ80 speed up MSX?

Post by Pierre Giel » Sat, 25 Sep 1999 04:00:00




>  "The Z80 and Z80180 instruction sets include an
>  RETI instruction that is used for servicing Z80
>  peripherals. Because the eZ80 does not include
>  these peripherals, nor does it allow them to be
>  connected externally, there is no reason to ever
>  conclude an eZ80 ISR with an RETI."

What kind of peripherals do you think they mean? The Z80 SIO or CTC,
etc.? As far as I know, the MSX does not use these.

Quote:>If the eZ80 runs 4 times faster than a Z80 at the same
>clock frequency, there's a potential for problems with
>memory i/o in an existing Z80 circuit -- particularly
>with slower ROMs.

I doubt if that is true. The eZ80 just executes instructions faster
*internally* because less clock cycles are needed per instruction.
That may affect timing loops but will it also influence bus speeds?
This question remains to be answered.

Quote:>I think a bigger potential hassle with the eZ80 is the
>mixed 16/24-bit architecture. Typical code that works in
>Native Z80 mode will crash in ADL mode, and vice versa.

If you only use it in Native Z80 mode, the eZ80 should be 100%
compatible with the Z80. There is no need for a new data type like the
24-bit integer, because only ADL mode requires this.

My point was that the eZ80 could make all MSX computers faster without
making them incompatible. That means replacing a Z80 with an eZ80
which runs in Native Z80 mode at standard clock speed (3.58MHZ).
If that is shown to be possible, it would already be a step forward.
After that, we can still experiment with the other posibilities, like
the TCP/IP stack or the MMU.

Pierre

 
 
 

Can eZ80 speed up MSX?

Post by Seliou » Sat, 25 Sep 1999 04:00:00


Quote:>My point was that the eZ80 could make all MSX computers faster without
>making them incompatible. That means replacing a Z80 with an eZ80
>which runs in Native Z80 mode at standard clock speed (3.58MHZ).
>If that is shown to be possible, it would already be a step forward.
>After that, we can still experiment with the other posibilities, like
>the TCP/IP stack or the MMU.

Well, if you can get it done on hardware, I can help you create a eprom with
compatible code (if RETI is unavaillable) to test it.

At 7 Mhz, it would be 8 times faster than a normal MSX ?? That is VERY
interesting !

 
 
 

Can eZ80 speed up MSX?

Post by G.S. Vigneau » Sat, 25 Sep 1999 04:00:00


Quote:>What kind of peripherals do you think they mean? The Z80 SIO or CTC,
>etc.? As far as I know, the MSX does not use these.

That's correct -- standard MSX doesn't utilize the Z80 IEI-IEO
feature. My remark was a general comparitive comment on the Z80
versus the eZ80. On this point, I think that the preliminary document
is skewed; the eZ80 very likely does support IEI-IEO.

Unfortunately, the eZ80 data doesn't include timing diagrams which
would reveal if there may be bus-speed issues.

Based on the early technical data, my opinion is that the eZ80 *can*
be used -- via a daughterboard -- to directly replace a Z80 or Z180.
I'll  certainly be  trying it with my Spectravideo-328!

Regards,

Greg_

http://home.korax.net/~telic
September 24, 1999, Toronto.

 
 
 

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