Harddrive read speed in WinUAE vs real Amiga

[remz]

Hi Toni and everyone,

I was toying with streaming data from the harddrive, and it made me wonder: Is WinUAE emulating the harddrive speed too? I didn't find any settings in WinUAE, contrary to floppy disk, to manage emulation speed of the disk.

I was wondering if we know, on average, with Kickstart 1.3 or 2.0, with a mechnical harddrive, about what kind of read speed we can obtain on a real Amiga 68000 + just chip ram, to be able to estimate what is feasible in term of 'direct disk streaming'.

[paraj]

Pretty sure the answer is that WinUAE doesn't emulate drive speed.
As a quick test I whipped up a program that times reading a file to chip mem.
On my A1200 with CF-card adapter I get ~970KB/s reading from a FFS partition (with or without 060 enabled).
In WinUAE with A500+ cycle accurate setup (I was lazy and used ReadEClock, so KS2.0+ needed) I get ~43MB/s.

[patrik]

Originally Posted by paraj

Pretty sure the answer is that WinUAE doesn't emulate drive speed.
As a quick test I whipped up a program that times reading a file to chip mem.
On my A1200 with CF-card adapter I get ~970KB/s reading from a FFS partition (with or without 060 enabled).
In WinUAE with A500+ cycle accurate setup (I was lazy and used ReadEClock, so KS2.0+ needed) I get ~43MB/s.

With 43MB/s, it appears chipmem speed is ignored when reading to chipmem .

[remz]

It might appear "0 clock cycle" for the Amiga side when the emulator performs the real read on the host platform, and this imply the data is directly "injected magically" intio the destination memory buffer?
(because as we see, even a pure copy cannot much such speed)

[paraj]

Originally Posted by remz

It might appear "0 clock cycle" for the Amiga side when the emulator performs the real read on the host platform, and this imply the data is directly "injected magically" intio the destination memory buffer?
(because as we see, even a pure copy cannot much such speed)

Yes, haven't checked if that's actually the case, but it appears to be how it works (Using a HDF seems to be a bit slower (~5MB/s) rather than a shared folder, but maybe that's just a coincidence).

In other words, you probably shouldn't rely on WinUAE for testing how fast you can stream data from a HD on an A500. For that you probably want real-world testers or at relevant datasheets (and I guess if the disk is OFS and fragmented you have to provision for additional seek time for each block).

EDIT: Maybe there are some advanced emulation options I'm not aware of, so the above just goes for using plain shared folders/HDF.

[Toni Wilen]

DMA controllers are "immediate". PIO controllers are affected by CPU emulation mode.

Speed control does not exist. It isn't trivial.

[remz]

The next thing I wanted to try would be streaming from CD (at CDTV speed): I assume WinUAE does implement CD read speed emulation?
(Because I see a checkbox for enabling 'turbo CD speed')

[Toni Wilen]

Originally Posted by remz

The next thing I wanted to try would be streaming from CD (at CDTV speed): I assume WinUAE does implement CD read speed emulation?
(Because I see a checkbox for enabling 'turbo CD speed')

Yes, CDTV and CD32 has "real" CD speeds. (CDTV=1x, CD32 drive is 1x/2x, software controllable)

Correct speeds are needed because CD read speed and CD frame interrupts are used for timing.

btw, directory filesystem won't ever have speed limits because it isn't a block device but a filesystem. Hardfiles can be supported but is also very boring task to implement..