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XDMA32/XCDROM32 VirtualPC and VirtualBox issues (Emulation)

posted by Japheth(R) Homepage, Germany (South), 11.12.2007, 11:31
(edited by Japheth on 11.12.2007, 11:45)

VirtualBox is based on Qemu. It uses a different BIOS which apparently hasn't Qemu's problem and allows to find the UDMA IDE controller without using XDMA32/XCDROM32's /P option. However, there's a problem with DMA in VirtualBox v1.52. I could only run XDMA32 reliable when using the new /B switch, which causes all reads to use the XMS buffer. Speed boost is still significant, fortunately (> 200%). Sample:

DEVICE=C:\JLOAD.EXE XDMA32.DLL /B


MS's VirtualPC 2007 is also somewhat strange. It's IDE controller supports DMA, but not UDMA. Therefore, to use XDMA32 and XCDROM32, one has to use the new /W switch, which allows the drivers to accept devices capable of "Multiword"-DMA only. For XDMA32, the speed increase is not significant (about 10%-15%), but using XCDROM32 with /W option boosts speed more than 100%. Sample:

DEVICE=C:\JLOAD.EXE XCDROM32.DLL /W

(use the drivers found in XJLM.ZIP)

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MS-DOS forever!

 

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