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To: RagTimeBand who wrote (2616)	6/12/1998 12:09:00 PM
From: Mark	Respond to of 5944

What about off-loading the CPU's workload? Emory I guess there are three possible things you might be refering to - 1) Controller command management - Whilst most SCSI controllers are script driven, the newer EIDE controllers are also. 2) Interrupt overhead - I cannot think of any reasons why there should be any significant difference between the interrupt overhead of a script-driven EIDE vs. SCSI ? 3) Cache management - A SCSI drive has integrated cache management which an EIDE drive does not. The host would have to perform this activity in an EIDE arrangement, which would be an increased overhead. However, my experience of ADVANCED operating systems (not Mickey-soft) is that the disk driver software likes to have good control over all of the disk transfers - i.e. it has it's own cache/track/etc., management routines, which somewhat minimises the benefit of the integrated SCSI caches. So, yes I agree that EIDE places slightly higher demands on the host, but only in respect of the disk cache. If the high-end OS's define how the mass market will go, then in time it is likely that NT, etc., will want to have more control over the HDD track management, etc., so this will become a non-issue. Mark

To: RagTimeBand who wrote (2616)	6/12/1998 5:04:00 PM
From: OrionX	Read Replies (1) \| Respond to of 5944

Hello Emory, What about off-loading the CPU's workload You're absolutely correct on this point. Most average people and some so called experts also don't understand this point either. I'm sure many of your have read some of the product comparisons with regards to CDROM drives. Why is a product such as one from Plextor more efficient when reading data (program installs, games, data retrieval) by using much less of the CPU cycles than one with an EIDE interface? As low as 30% CPU utilization for a good SCSI CDROM drive versus up to about 90% for an el cheapo EIDE drive. Surely the on board cache size makes a big difference but also the ability of the SCSI I/O susbsystem to manage data access mostly on its own without the constant need of the CPU involvement gives the CPU time to address other things. The bottom line, SCSI offers system efficiency. I get better I/O on my P166 with a SCSI CDROM drive than I've seen on many store demos running P266 with their run of the mill CDROM drives. With many programs, specifically games, running off the CD, it makes sense to have a good I/O balance to avoid those jerky screen refreshes. It baffles me that many people will spend like crazy on a new video adapter 200$+ but then run their new 3D games off a 79$ CDROM drive. Looks to me like people aren't getting really educated on how their PCs actually work. Maybe Intel et al want to keep things this way.