Author
| eZ80 + FPGA
|
EVPON
msx lover
Posts: 93 |  Posted: February 17 2007, 14:30 |
Three questions:
1. It would be possible to make a MSX with the eZ80 + FPGA for the
other MSX IC’s?
2. This possible MSX would be fully functional?
(problems with external hardware apart)
3. What are the pros and cons?
|
|
AuroraMSX
msx master
Posts: 1227 | Posted: February 17 2007, 17:47 |
Quote:
| Three questions:
1. It would be possible to make a MSX with the eZ80 + FPGA for the
other MSX IC’s?
|
Well, there is an MSX using just an FPGA on its way ( One Chip MSX), and having an extra eZ80 can't hurt 
Quote:
| 2. This possible MSX would be fully functional?
(problems with external hardware apart)
3. What are the pros and cons?
|
Search MRC for discussions on the OCM and you"ll find questions like these and others addressed aplenty. |
|
EVPON
msx lover
Posts: 93 | Posted: February 17 2007, 19:02 |
Yes, I read the OCM discussions continuously, but my
main question is if the eZ80 (8 bit , 50MHz clock speed)
can be adaptable to the structure of the MSX without
problems. I commented the FPGA part because now is the
best solution.
|
|
ARTRAG
msx master
Posts: 1587 | Posted: February 17 2007, 19:06 |
no way,
you need cycle accuracy to run msx games
this is the reason why msx TR had TWO CPUs,
z80 AND R800
the latter can run z80 code, but without
cycle accuracy, you cut away 80% of the
existing SW
|
|
AuroraMSX
msx master
Posts: 1227 | Posted: February 17 2007, 20:27 |
Quote:
| no way,
you need cycle accuracy to run msx games
|
Really? I think this may be true for demos and newer games, that rely on nifty raster effects, but most of the older MSX soft should run just fine.
I remember playing all kinds of games just after I upgraded my MSX2 to 7MHz and finding most of them perfectly playable, apart from the fact that the sound was a mess. I'd say you could run about 80% of the existing software 
And ehm, the eZ80 should be able to handle 3579545Hz (thank you, manuel) as well. In that case, I don't see why it should not be possible to make an MSX out of the eZ80/FGPA combo...
|
|
msd
msx professional
Posts: 607 | Posted: February 17 2007, 21:40 |
A ez80 on 3579545Hz is still faster than a z80 on 3579545Hz .It uses less cycles per instruction
|
|
DamageX
msx freak
Posts: 162 | Posted: February 18 2007, 07:49 |
When MSX is ALREADY OBSOLETE, I don't see why anyone would insist that any new product still has to be cycle exact to run old games.
Aren't you glad your PC still has a 4.77MHz 8088 in it so that you can play that old snake game without it running too fast? Er...
I bet a 50MHz eZ80 can run a cycle exact 3.5MHz Z80 emulator.
|
|
dvik
msx master
Posts: 1302 | Posted: February 18 2007, 08:06 |
If you want all existing titles to run correctly you need to be cycle exact with old MSXes. But maybe it doesn't matter if 5 or so % of all games doesn't run correctly. Most games will run even if the z80 isn't cycle exact.
Only problem is for developers that want to use new machines to develop games that is supposed to run on old machines as well. Then the new machines has to be cycle exact or otherwise they are useless.
|
|
EVPON
msx lover
Posts: 93 | Posted: February 18 2007, 14:27 |
The Zilog web page says:
"The eZ80® executes Z80 code four times faster than traditional Z80s at the same clock speed"
On the other hand I also asked about ez80 at the HispaMSX. A user
said eZ80 has internal devices in the 00-5f area, obligatory in the MSX structure. Then this hypothetical MSX (eZ80 + FPGA) would not be viable .
|
|
msd
msx professional
Posts: 607 | Posted: February 18 2007, 15:23 |
The location of the internal I/o registers of ez80 can be programmed anywhere between 00 and 0xff.
|
|
|
|
|
