VOGONS

Search

Common searches

To be or not to be? Local bus IDE or ISA SCSI?

Topic actions

First post, by aries-mu

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie

Hi guys
Compaq Prolinea 4/66, 486 DX2 66, only ISA slots, nothing better.
Motherboard's local bus IDE (not EIDE!), which if I’m correct should have a 5 MB/s speed (am I wrong?).
With IDE drives it wouldn’t be a problem as they were turtles.
But I’m using a nicely fast IDE to SD card adapter, and the SD card is pretty fast.

I never considered installing an ISA SCSI card, a SCSI to IDE converter, and a fast CF card, because of ISA slowness and bottleneck, but now I’m wondering if the old IDE channel is a bottleneck worse than the ISA bottleneck.

In theory a 16 bit ISA should get to 16 MB/sec, which, vs the 5 MB/sec of the IDE channel, should favor the SCSI ISA CF card against the IDE – SD card (please don’t focus on SD/CF, they’re similar, just the CF doesn’t wanna work on that IDE controller).

What would be faster?

The main doubt, I guess, is what's exactly the "IDE" mode of the motherboard...
Because if it's PIO mode 2 or DMA Single Word 2 it's already 8.3 MB/sec.

Thanks

They said therefore to him: Who are you?
Jesus said to them: The beginning, who also speak unto you

Reply 2 of 6, by aries-mu

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie
derSammler wrote:

SCSI is always faster, because it's independent from the CPU. It has it's own processor and does all the work, unlike IDE.

Wow this sounds interesting!

But, wait a sec., somehow sooner or later the data must pass through the CPU! For example, you run a photoediting app, or a demanding game, the CPU reads the data from the drive, so the data must get to the CPU after crunched in the SCSI processor... and vice versa... What about the speed in these steps CPU → SCSI chip → CPU ? they would go through ISA...

Thanks

They said therefore to him: Who are you?
Jesus said to them: The beginning, who also speak unto you

Reply 4 of 6, by aries-mu

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie
derSammler wrote:

The data must go into RAM, and that's what the SCSI controller does on its own.

😕
I'm confused sorry...
I mean the RAM must communicate with the SCSI controller. The only connection between the 2, again, is the ISA bus... so, still, no matter how fast the SCSI chip is, it cannot provide data faster than the ISA bus... am I correct?

They said therefore to him: Who are you?
Jesus said to them: The beginning, who also speak unto you

Reply 5 of 6, by derSammler

Posted on 
User metadata
Rank l33t
Rank
l33t

Yes, but that doesn't matter, as the SCSI controller takes full control over the ISA bus to transfer the data into RAM. The 16 MB/s are not a real limit as you probably won't find a fitting hard disk that can constantly read more than 16 MB/s from the media anyway.

Reply 6 of 6, by aries-mu

Posted on 
User metadata
Rank Oldbie
Rank
Oldbie
derSammler wrote:

Yes, but that doesn't matter, as the SCSI controller takes full control over the ISA bus to transfer the data into RAM. The 16 MB/s are not a real limit as you probably won't find a fitting hard disk that can constantly read more than 16 MB/s from the media anyway.

I'm starting the get the taking control over thing... However that would apply to hard drives.
I would use, on the contrary, a net measured 250 MB/sec both read and write CF Card (300 MB/sec theoretical) via a CF-to-IDE adapter → SCSI to IDE converter

With the IDE channel, I'd also use a super fast SD card via IDE to SD converter.

So, if the super fast SD card is able to fully saturate the IDE channel, compared with an ISA-bottlenecked SCSI I wonder what's better...

They said therefore to him: Who are you?
Jesus said to them: The beginning, who also speak unto you

Go to top of page Go to top of page
Back to General Old Hardware
Close window
Close window