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Posted By

Litwr
on 2014-10-28
01:39:41
 Re: Z80 GUI: SymbOS

Dear JamesD, I am very sorry - I noted you edit lines only today.
Amstrad CPC and PCW wait states system is very easy. It rounds all the instructions time to the upper 4*n states. So JP NNNN will take 12 states, LD A,B - 4 states, etc. The every raster line provides 256 states (64 NOPs - *EDIT*) for CPU. Amstrad CPC has one of the best for the 8-bit world video system with 16 KB RAM. The speed of the video RAM is the same as other RAM or ROM.
Xlife-8 project makes some changes in the Amstrad CPC world - It caused the appearance of the Yagol -
http://www.cpcwiki.eu/forum/news-events/xlife-8-for-cpc6128-is-released/msg86121/#msg86121
http://www.cpcwiki.eu/forum/applications/yagol4cpc-alpha-release/msg88036/#msg88036 :-)
BTW the close work with z80 shows that you are right: the 6502:z80 speed ratio for the updated Xlife-8 is close to 2.4:1 (or 3:1 with Amstrad's wait states). So Commodore 64 Xlife-8's performance is close to Amstrad CPC at 2.8 MHz, Commodore+4 - 3.4 MHz, Commodore+4 with blank screen - 5.1 MHz, Commodore-128 - 6 MHz, PAL Commodore +4 at the NTSC mode - 6.4 MHz.
I have also a question for you. Do you know any reason why the best 8 bit CPU 6809 was so underclocked (only 0.89MHz at the Dragon-32/64 and TRS-80 Color)?



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