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Yes and No (Announce)

posted by Japheth Homepage, Germany (South), 28.11.2007, 10:52

> Yes, but these 1.75K can be in upper memory (so no low memory is used), if
> you specify DEVICEHIGH=UIDE.SYS in CONFIG.SYS, and it's for a HDD/CD/DVD
> cache size of up to 200MB (a few KB more are taken for a cache size of up
> to 1GB), whereas neither XDMA[32] nor XCDROM[32] do any caching. Plus
> there are other drawbacks of the old XDMA/XCDROM too (bugs, less control
> and compatibility, and so on).
Some remarks from me:

1. According to the "official" UIDE site it is "Gone Forever" (http://johnson.tmfc.net/dos/drivers.html). It seems a bit strange to compare XDMA32 with something not available at all. It probably can be found on your boot disks images, but these also contain "stolen" software, which some people want to avoid to download.

2. Caching is sometimes good, and sometimes it is bad and can even slow down things. I prefer a cache available as a separate module. And I also prefer to use extended memory for 32bit protected-mode DOS programs, and not waste it for a cache if the system includes fast SATA drives. Therefore, the original QDMA, which just cached 1-sector reads in a 256 kB buffer, was a better thing IMO.

3. Yes, there were some bugs in XDMA, but it is SOFTWARE and those bugs are/will be fixed finally.

4. UIDE has to do up to 5 switches to protected-mode during an Int 13h when running in v86-mode (2 VDS + 1 Int 15h + 2 A20). Not that this does matter a lot as far as speed is concerned, but it clearly shows that a driver running in protected-mode is the BETTER design then.

---
MS-DOS forever!

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