On Mercredi 12 Septembre 2001 18:39, Wolfgang Lenerz wrote:
> Hi all,
>
> I've recently had some time to play around with my all new Q60.
>
> I'm very happy with it, it is a nifty beast.
Yes indeed !
> This also gave me the opportunity to test the CD driver. Indeed, I (of
> course) waznted to get my usual setup also going on the Q60. Sp I
> copied my QPC QXL.WIN fimle to a CD (i've written abaout this
> before) and, with the help of many of you, actually managed to het
> it going.
> I had to change one instruction in the ATAPI driver, else it would
> completely crash the machine, but, once that was done, it works (if
> anyone is intered in the tweak, contact me, I'll be sending an email
> to Thierry a bit later to tell him about it, as well).
I wonder what this instruction is as none of the beta-testers had
reported any crash so far...
> I then used the QXLTOOL utility to transfer my files (about 40 MB
> in a 70MB qxl.win file).
>
> The good point : IT WORKS. I was able to tranfer the files from the
> qxl.win CD to the hard disk. As far as I can tell, there was *NO* file
> corruption or anything.
Then you are lucky as I DID experiment some files corruptions (I guess
qxltools does not retry when an error occurs and read-retry after error
is not yet implemented into the CDROM driver)...
> Hats off to Thierry and J. Hudson.
Thanks, but as far as I am concerned, the work on the CDROM driver is
_far_ from being over.
> The bad point is: it is really s-l-o-w. the 35 MB mentioned above
> took about 36 hours (yes!) to transfer.
No wonder here: there is simply no caching mechanism implemented so far...
> I don't know whether this is
> due to the driver or QXLtools, I'll attempt to find out at a later stage.
In fact this is due to both:
- the driver lacks caching and must reads at least 2Kb of data each time
2Kb or less is to be read (you can't read less than 2Kb of data from a
CD).
- qxltool issues a read for each filename, file length, date, dataspace,
(etc...) fields and, as the QLWA filesystem got 512 bytes per sector,
it reads 512 bytes at a time (combined with the missing caching of
the driver, this means that in fact each 512 bytes block is read 4
times from the CDROM !).
> It was very noticeable that copying files thatlay towaords the end of
> the disk took MUCH longer (at the same file size) than some that
> lay at the start of the disk.
Here again the reason is lack of caching: each time a file is copied,
qxltool gets the sector numbers from the FAT which is located at the
start of the disk and then go get the corresponding sector; I suspect
it does so for each sector of a file (there is therefore as many head
moves as there are 512 bytes blocks in a file !).
As I wrote previously: the QXL.WIN file access on CD-R was just a quick
hack. The driver is still in an early alpha state and will only go beta
once proper error recovery/correction and data caching is implemented.
QDOS/SMS forever !
Thierry (currently in Djibouti).
