Improve disk reading speed by sector order

[bugbiter]

I already tried several patterns with mediocre success. Instead of a 'dit dit.. dit dit..' sound I now get 'dit dit dit', But I want the fast 'dididididit' as when normally loading data.

There seems to be no resource as to what pattern exacltly Dos 2.5 for example hard formats the sector order. The strotmann document explains a lot but claims the sectors are numbered 1-18 in a straight circle (including sector 19 which is not used) but I am sure it must be kinda half-turn interleaved just comparing spin frequency and beeping rate.

Does anyone know more about the interleave layout? I think it's key for mastering this issue.

[Rybags]

Dos doesn't specify the interleave. In the vast majority of drives it's in a fixed order, and nothing you can do to get it to format differently other than something like a Happy board or modified firmware.

 

I still think you're way better off using a buffer, and if you start doing compression stuff you'll need that and more anyway and your IO speed problem will also potentially get worse.

[1050]

__________________________
CUSTOM FORMAT
Command: f($66)
AUX 1: --not used--
AUX 2: --not used--

Notes: This command formats a disk in single/double/enhanced density modes
AND allows the user to specify the sector ordering. The computer
sends a data frame of 128 bytes to the drive. The first 12 bytes are
the configuration bytes, and the next 18-26 bytes are the sector
numbers in order. The STANDARD sequences are as follows:

Single density 17,15,13,11,9,7,5,3,1,18,16,14,12,10,8,6,4,2.

Double density 18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1.

Enhanced density
1,3,5,7,9,11,13,15,17,19,21,23,25,2,4,6,8,10,12,14,16,18,20,22,24,26.


The standard ULTRASPEED sector skews are:
Single density 4,8,12,16,1,5,9,13,17,2,6,10,14,18,3,7,11,15

Double density 1,14,9,4,17,12,7,2,15,10,5,18,13,8,3,16,11,6

Enhanced density
4,8,12,16,20,24,1,5,9,13,17,21,25,2,6,10,14,18,22,26,3,7,11,15,19,23.

 

Text version of SpartaDOS Construction Set manual. You want info, this is chock full of it.

http://atariage.com/forums/topic/226714-spartados-32d-manual-or-help/?do=findComment&comment=3014356

 

[Rybags]

Really, I see absolutely no sense in pissing about with custom formats. It won't make it much faster, you'll gain much more by doing layout and I/O optimisations in the program and pic format.

Plus, it'll make no difference in emulation and probably run worse on stock drives.

[Heaven/TQA]

don't see the point either... except for academic researches... memory layout reorganisation plus using packer would make more sense...

[flashjazzcat]

Yep: Sledgehammer and nut spring to mind.

[bugbiter]

OK, well.

 

I'll rearrange the Picture data so it can be loaded into memory in one go. I dont think I can get it faster than this. I only have to pause once to slip one pic into the RAM under the ROM.

 

And I won't be using any buffer at all, I'll make a custom boot disk, using SIO calls (jsr diskinv), pointing the buffer address directly to target memory. (Ain't that called burst mode?)

Edited September 23, 2014 by bugbiter

[ricortes]

One of the things I haven't seen mentioned yet is custom sector layouts are hardware specific with respect to speed. If you use the USD ultra speed layout it will actually be slower on a stock 1050 or 810.

 

IIRC: diskinv only works for 128 byte sectors. A custom boot disk is a fine choice since you can have the widest hardware compatibility with that format.