Emulated floppy speed

[stevendt]

SD Cased Version

I am finding that reading and writing to the SD card on the host system (not the PC used to create the card) is very slow, much sower than an actual floppy drive. I have tried SD cards up to class 6, but could buy class 10 if it makes an appreciable difference. Even with Class 6 though, I think that the speed should be far faster than it is.

Does anyone have any idea what might be wrong?

Does the FAT 32 allocation size make any difference to speed with the HxC?

Does the HxC slew setting make an appreciable difference? - If so, what is a good setting?

regards
Dave

[Jeff]

This is generaly an interleave/skew/gap setting problem : With the wrong interleave/skew/gap setting, the host machine may don't have the time to "catch" the next sector and must do some additionnal disk rotation to get it.
In the worst case the machine have to make 16 rotation to get the 16 sector present on a track... (0.2s *16 = more than 3s...)

To got the right interleave/skew/gap setting : update the firmware with the 1.8.1.7 (in your email box), and format one of your image on the host machine.
Send me back the image by email.

Anyway about the SD i recommend good quality sdcard model : Class 10 Sandisk Extreme Series is an good examples. I got one here and this is a very good card.

For industrial usage (24h/24h working during many years), SLC flash based SD are recommended.
Some examples :
http://www.psism.com/industrialsd.htm
http://www.atpinc.com/p2-4a.php?sn=00000395

[stevendt]

Hi Jeff,

thanks a lot for the reply. I thought that your e-mail had got lost, but I found you in "Spam"

That's great - I will update the firmware and send you a formatted image.

Thanks for the card info too - I will get one of the Sandisk Extreme cards that you suggest, I have had good experiences with lower class SD cards,

regards
Dave

[Jeff]

Waiting for the feedback

[Jeff]

The feedback :

Hi Jean-François

I can see where the "Jeff" comes from now


Thanks a lot -

That firmware has made a big difference! - I have not done any quantitative testiing yet, but the speeds are now much more like I would have expected.


The formatting seems to work fine, with an image previously created on the PC with my parameters, that I assume would have been "formatted" anyway?

Still, using the system's FORMAT command, the "disk" was (re)formatted fine and I could write, read and check it.


Just out of interest, I also copied an IBM 720K formatted image on to the SD card, and formatted that - it also worked well, overwriting the existing format.


[That leads to a question for a future "enhancement" - would it be possible to create a "blank" image on the card directly from HxC and then have the system format it as per its requirements?. i.e., to make it unneccessary to pre-populate the SD card?]


You can probably analyse the formats anyway, but the system that I am usiing (Memotech FDX, with a Type 07 Floppy) uses :-

DS/DD
80 Tracks
16 Sectors per track
256 Bytes per sector

The two formatted images are attached.

By the way, in HxC, what is the difference between MFM and IBM_MFM, both seem to be readable by my sysyem?

regards