Posted By
Litwr
on 2013-08-11
13:37:12
|  Re: Z80 GUI: SymbOS
@JamesD
Thank to you I'll become an Apple ][ expert soon.  You are right I missed disk controller. I was sure that CPU makes all job like at Commodore 1541/1551. So my mathematical speculation proves nothing for Apple ][ drive speed.
@MMS This gives us why C1541/1551 is limited to 4 KB/s. I'm not 100% sure about this result. We should ask disk drive guru (Gaia, IstavanV, Krill, ...) to know truth.
However the facts give us Apple ][ drive speed below 3KB/s. The file MUFFIN is at the distribution disk and can't be severe fragmented.
The interleave may speed up the specific DOS only. The interleave means nothing for an advanced DOS. IMHO EsDOS or DavidDOS are advanced ones. The advanced DOS may read sectors in any order. If sectors 1, 2, 3 were requested, for example, then this DOS may read sector 1, then 3, then 2. This DOS may calculate proper place for each sector in the memory. So it may place the last read sector to the start of data in the memory and the first read sector to the end.
The wiki article about Apple DOS contains the next phrase. ''The Apple IIGS operating system, GS/OS, would eventually employ an even more efficient "scatter read" technique that would read any sector that happened to be passing under the read head if it was needed for the file being read.'' It illustrates the idea given above.
My intention was to know the standard speed with the standard DOS. It is below 800 KB/s - it was good for earlier 80s. So our discussion is about maximum speed to load file. The facts give about 3 KB/s. Any theory without facts is speculation or an exercise of power. 
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