Marco wrote on 2024-04-03, 19:32:Sorry to reopen but again found a point that is making up my mind. […]
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Jo22 wrote on 2017-09-03, 16:46:SmartDrive can be counter-productive on slow systems.
Especially if you've got a fast HDD or a flash medium already. […]
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SmartDrive can be counter-productive on slow systems.
Especially if you've got a fast HDD or a flash medium already.
I think SmartDrive makes sense for single-speed CD-ROM drives, though.
150KB/s are barely enough for CD-ROM games with FMVs.
Sorry to reopen but again found a point that is making up my mind.
I read this statement already somewhere else but never could find a prove for this.
It could only be about cpu utilization. As i benchmarked on my 386sx DOMs, CFs and large 16MB Cached HDDs. Read/Write instructions where always faster with smartdrv. I timed various copy operations for that. My explanation is that access to memory ram is always faster than the access via PIO - even there is a fast hdd or large cache behind. It will still be behind the PIO I/Os
Hi there! I believe at the time I was thinking mainly about SmartDrive on slow 286s and SmartDrive on 386/486s in conjunction with the usual memory managers (v86 can slow them down).
Because, to be really useful, SmartDrive requires lots of memory for buffering/chaching data.
So either EMS (fast via chipset/dedicated board) or Extended Memory is being required in some form.
I really recommend trying out the cloaking-enabled SmartDrive versions (Helix products).
They don't require EMS or help of v86 based memory managers.
Another factor to consider is linear reads vs random reads.
Playing back a wave file or movie is different to reading a couple of data files.
That's like with the issue with modern NCQ enabled hard disks (native command queueing).
In theory, NCQ is great (elevator principle, in which every floor is being reached in most efficient way), but it can also slow down linear access.
So it really depends on how the caching algorithm works, I guess.
Some programs are sector based (SmartDrive?), while others are FAT/file based (FastOpen).
The 150KB/s CD-ROM drive are (were) sort of a dilemma, I think.
They can't buffer any meaningful data and do always "squeak around" a lot (thinking of the Mitsumi LU005S here):
There's always lots of head movement involved, for each file being accessed.
So at this point, I think, SmartDrive can't hurt performance anymore here.
Any type of caching being done (be it reading ahead in a linear fashion or be it reading random, nearby sectors etc) reduces erratic head movement, even if there's little actual performance being gained.
The use of a cache makes it effectively slower sometimes, maybe, but at least the erratic head movement goes away.
The drive will operate more smoothly, all in all.
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
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