[Techtalk] Largest hard drive useable with an Intel Celeron 466

[Alvin Goats]

> I'm thinking of building a fileserver using an Intel Celeron 466 I have.
> What's the largest hard drive that I could use with that processor (or,
> if the answer is "depends", how do I find out)?
> 

The CPU is not where the issue resides, although it and the motherboard
dictate what speed the bus interface is and subsequently what devices
can be optimally added to the system performance wise. 

The problem is ultimately always with the hard drive controller chips.
The BIOS may have some limitations, but once a partition of a type and
size the BIOS understands gets booted, the OS can take over and do more.
This was the 'trick' used by Ontrack and others to get around the
original IBM PC BIOS limits for DOS. Linux uses similar tricks to break
some barriers. 


So....you need to find out what type of controller chip you have and
research the limits of that chip.

The original IDE interface couldn't handle more than 504M hard drives,
the EIDE (or ATA-2) added LBA (logical block addressing) which broke
most of the memory barriers. You probably have an EIDE interface with an
enhanced DMA (UDMA/33 or maybe a UDMA/66). The UDMA is simply the
interface maximum burst mode speed. The interface is only a transfer
point, addressing (or capacity) is done inside the hard drive (the
controller chip is on the drive and not in the controller card or
motherboard). 

There are sometimes some issues with running a higher level UDMA device
on a lesser one (timing issues with the bus interface) which should be
looked at with the disk drive manufacturer (UDMA/100 drive on a UDMA/33
bus). There are modes and PIO's with the EIDE interface that had some
limits, but if you have a UDMA/33 or higher, you shouldn't have any
issues with running really large drives. 


Ancient MFM, RLL and ESDI drives were "dumb" drives, the controller chip
is in the card or motherboard and the limit was at the board. Again, the
board issue was really the controller chip. 

SCSI controllers have similar issues for disk drives as MFM/RLL/ESDI. My
Adaptec AHA-2940AU has a limit of an 8GB disk, and a maximum of 7
drives. Capacity limits vary depending on the interface (narrow or wide)
as well as the chip set. Firewire currently has a 200GB drive being
offered by Western Digital, so the capacities are much higher. And the
firewire can daisy chain up to 62 devices vs. the 7 I have. Hmmmmm
...... 200GB x 62 devices ... 12.4 TB? mmmmmmmmmmmmmmm


Now, if you want to go to extremes ..... ;):   

EIDE motherboard chips can typically handle 4 drives, assuming one is a
CD, then you have 3 drives to use. You can add additional USB drives
(assuming your Celeron card has a USB interface) and add as many drives
as the bus allows. And you can add a SCSI or Firewire card to add as
many drives as you can fit on the SCSI or Firewire bus. That gives you 3
different simultaneous interface paths and as many disk drives as you
can stick on each one with the drive capacity limits that each possess.
SCSI and Firewire can be addressed so that you can run multiple cards,
so if you have the space for additional cards ....

And this methodology can be done on a 386SX-16 with linux, if you don't
mind waiting a few seconds or so. Just think, a 386SX-16 with a terabyte
of storage! ;)  

Reasonably, a 486DX-66 can make a good fileserver, so anything faster is
that much better. A lot of places have looked seriously at adding server
capacity by resurecting old 486's and Pentiums with Linux. 


I hope this helps you some, if so let me know.

Alvin