Padial's eMSX2++ - how soon and how much?

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Van Sonic_aka_T

Enlighted (4130)

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12-05-2004, 14:31

It should be.

Van anonymous

incognito ergo sum (116)

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12-05-2004, 14:40

It should be.

But R800 compatibility can have an an other implementation then the original design.

See AMD and Intel..and therefore other CPU performance..

Or am I talking B*llSh*t?

Van anonymous

incognito ergo sum (116)

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12-05-2004, 19:15

But R800 compatibility can have an an other implementation then the original design.

See AMD and Intel..and therefore other CPU performance..

Or am I talking B*llSh*t?
That's correct.
Basically R800 is a better implementation of the Z80 design. (Plus the added multiply unit ofcourse).
Improving upon the R800 implementation is hard, as it already executes one instruction per clock.

There are 2 ways you can improve the speed:
1. Increase clockfrequency. This needs FAST RAM, as the R800 already uses a few tricks to get the maximum performance out of its (IIRC) 150ns RAM. Any clock increase will need to be coupled with faster RAM. Ofcourse RAM nowadays is as fast as 2ns Smile

2. Make a superscalar implementation, which means executing more than 1 instruction in parallel each clock. This massively complicates the architecture, putting the Z80 on the level of the Intel Pentium, complexity-wise.

Van [D-Tail]

Ascended (8258)

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12-05-2004, 20:50

About the memory access times... I heard the GT and ST had another type of memory. IIRC the GT memory had a lower access time (not much, about 10ns or so, but still... Wink)

Van anonymous

incognito ergo sum (116)

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12-05-2004, 21:06

Actually, GT's are normally a bit slower than ST's. It has to do with the refresh period needed for 512K which is higher than with 256K or 1024K(!).

The effective speed of a R800 using 256/1024K is 6.72MHz, while with 512K it is 6.47MHz.

This info comes from a cpu speed utility written by AtoC, a japanese MSX expert.

Van [D-Tail]

Ascended (8258)

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12-05-2004, 23:44

YAY! I've got the owning Turbo R then Smile A1ST w/256 kB RAM! No memory expansion for me anymore Smile Big smile LOL!

Van dhau

Paragon (1570)

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13-05-2004, 05:16

Hey man, 256 KBytes is quite enough, but 512KBytes or better yet 4MBytes are so much better... Even if GuyveR800 is right about CPU speed, most of the time you will run in Z80 mode, so it's irrelevant...

Van anonymous

incognito ergo sum (116)

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13-05-2004, 13:14

I dunno about you, but 90% of the time I use my turboR, I'm running in R800 mode.

Van IC

Hero (557)

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13-05-2004, 22:57

wasn't there a tool called chgcpu to change it to R800?!

Van Sonic_aka_T

Enlighted (4130)

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13-05-2004, 23:22

There is, but it'll boot on R800 by default. Unless you're using like DOS1 or old software. What surprised me though, is that a lot of games run just fine in R800 mode.

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