Posted By
Litwr
on 2013-08-11
13:35:13
|  Re: Z80 GUI: SymbOS
@JamesD
You eventually got a fact - [http://www.faqs.org/faqs/apple2/faq/part6/]. I've just downloaded DOS 3.3 System Master disk and by a2tools got MUFFIN. Its size is 27 sectors or 6397 bytes. So the speed according to the given link is 718 bytes/sec for standard DOS (50% slower than C1551 standard speed) or 2782 bytes/sec for enhanced EsDOS (this is slower that C1541 turbo mode).
It is the real speed - it is not just math speculation! So I have to say that Apple II is not so closed as I thought earlier. :-)
Let's try to calculate maximum speed for 1MHz 6502. If we want to have 10 KB/s data flow then we should get 100 KBit/s of raw GCR-data. It gives us 9 cycles per bit (10 cycles are reserved to the whole byte processing). 9 CPU cycles mean 2-4 CPU instructions which should distinguish 0 from 1 and pack bit into byte. Please make you own conclusion.
Thank you again! 
@MMS
I have to repeat that I am astonished by Commodore 8250 drive. It can use 1.1 MB per double density floppy! The gigantic IBM could make 1.2 MB at 1984 only and only for expensive high density media. IBM hardware allows to use only about 800KB for double density disk. So Commodore disk hardware were very advanced for 1980. It is mystery why they stopped to develop and even to use so good technology.
**edit @JamesD
Apple IIc plus has 4MHz CPU. It theoretically allows to read a track per one revolution and got 20 KB/s but the real transfer rate maybe lower. It is very difficult to get real numbers about Apple worlds. :-( Apple IIc plus uses special disk controller so CPU doesn't have to make all things but wiki says that this controller is not necessity for 4MHz mode. Such calculation for C128 2MHz mode should get 10 KB/s but C1571 burst mode gives only 3 KB/s. :-(
|
