RE: Hard drive on the EPP

["John H. Kim" <jokim@mit.edu>]

In message Tue, 25 Oct 94 16:06:07 PDT,
  george@cs.nps.navy.mil (Robert George)  writes:

>> data off the platter at 500k/s - 1MB/s.  If your drive is rated at
>>  10MB/sec and it has a 256k cache, the maximum time penalty for using
>>  EPP is waiting 0.25 seconds instead of .025 seconds.  In typical use,
>> you'll barely notice the difference.

> Wrong!

*Ahem*  Quite enthusiastic today, aren't we?  :-)  I'll concede, you win.
Although I still say for perhaps 50+% of the drives out there the
performance of EPP will be acceptable.

> The ThinkPad's disks have a data transfer rate off the platter of
> 24.5 - 35.8 Mbits/sec (quoting from the IBM internal technical documents).
> This, of course, equates to ~ 3 - 4.5 MBytes/sec.

Curious.  What are the specs on the 340MB drive?  How come Norton insists
I'm only getting 982k/sec throughput?  I'm a little chagrined at you calling
the throughput of my drive "state of the art 3 years ago."  If the 540MB or
810MB drive is 3-4x faster than the 340MB drive, I'm going to save up my
money.

>>   Most of the older disks I know of are 33 sectors/track and 1800 rpm.
>>    3600rpm disks started showing up in force a couple years ago, and
>>  5400 rpm  disks are still pretty rare (usually advertised as optimized
>
> The Micropolis SCSI-2 drive I just bought for my PC rotates at 5400 RPM --
> and it wasn't outrageously expensive.

Well, I never said they were outrageously expensive.  Just rare - you're
typically not going to get one unless you find out which models have the
faster spindle speed and specifically order it.

>> I have no idea what the specs on the TP's hard drives are.
>>
> The IBM drives spin at 3800 RPM, and have 112 sectors per track.

Say, since you've overflowing with all this info on the TP drives, do you
know where we can buy a case for it, or where we can buy the funky little
connector inside the case?  (Actually, I've tracked down the plug at the
drive end, it's just the cable and the TP plug I need)

> out there who have desktop PC's with Fast SCSI-2 controllers, try turning
> off synchronous transfers, which will drop your bus transfer rate from
> 10 MBytes/sec to 5 MBytes/sec.  You will notice a severe performance
> degredation under _normal_ DOS and Windows applications.

Since I doubt your drive is capable of >5MB/sec sustained transfer, would
you care to speculate what causes the performance degredation?  It may be
useful to know, since what you're saying is that drops in throughput beyond
the sustained transfer rate of a drive (i.e. transfer rate of 5MB/sec
dropped to EPP's 1MB/sec on a 900k/sec SCSI drive) can cause a severe
performance hit.
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John H. Kim        | "Mike Espy simply forgot he was no longer a Congressman."
jokim@mit.edu      | -anonymous, on the Secretary of Agriculture's resignation
jokim@uni.uiuc.edu | due to conflict of interest charges for accepting gifts.
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