Quadra/Performa 630 HDD question

[Themk]

Can a SCSI hard drive be attached to the SCSI bus that is used for the CD-ROM drive?

I know it comes with an IDE drive; which I plan on keeping, I was just wondering if I could stuff in a second HDD (the one I am thinking of would be SCSI). Oh, and I would also like to keep the CD-ROM drive too. Now, I know that the connector on the edge of the logic board is a little bit nonstandard, but there has to be a 50-pin connector somewhere for the CD-ROM drive, so using a multi ended cable I should be able to keep the IDE HDD, the SCSI CD-ROM drive, and add a SCSI HDD. Correct?

Thanks

 

[Johnnya101]

Yes. Like with external drives too. If you've got an external scsi drive, you can make it a cd rom.

 

[Themk]

Great. I was looking at service source (is that the right name?) and it talks about the scsi adaptor for the CD ROM. Just got to get a multi ended scsi cable, and it should be good.

 

[Brett B.]

It has been a few years since I've had my LC630 opened up but I can tell you that it's not as simple as plugging in a cable.  The logic board edge connector (inside the computer, not on the logic board itself) has built in ribbon cables for SCSI, IDE, etc... there is no internal 50 pin connector on the logic board, the SCSI cable is part of the edge connector.

You may be able to use some sort of 50 pin passthrough connector attached to the back of the CD-ROM drive, although space may be a concern.  I also don't think you'll have enough Molex power connectors for three drives at once... or enough space inside the computer for the second hard drive, for that matter.  Perhaps above the logic board.  In any case, I would be worried about the extra heat and power draw.

Bottom line to me would be to use a larger IDE hard drive if storage capacity is your goal, or an external SCSI drive.

 

[Themk]

This was kind of a "what if" question. I want to see if I can hack A/UX on to this. A/UX doesn't support IDE, but it does support the SCSI controller. That was my motivation for a second SCSI HDD.

Molex power connectors are solved by a simple splitter. Mounting the drive is not a concern; I can easily fabricate a mounting sled. Thank you!

 

[Trash80toHP_Mini]

A/UX can run on the 630 architecture? Whatever  .  .  .  not my thing:

Hacking the loom leading from the edge connector to the CD bar (edge connector) is doable. Split the cable to free up the proper 50 lines. Punch a 50Pin IDC Male connector to that center section and there's your internal SCSI port. There's room to spare under the CD bay for a SCSI HDD installation, so make sure you orient the connector correctly in terms of keying and pointing it at the stealth bay. Use a standard F<->F SCSI cable to make your connection. CD's terminated, but you should be ready to use an active terminator on the SCSI HDD if needs be, the Y cable setup isn't strictly kosher.

edit: don't recall if there'd be room, but you could cross cut those split away 50 lines to install a pair of the male connectors. Then you can use a standard multiple position cable to reestablish the severed CD connection, keeping the configuration of the cable linear. Stuff as many SCSI bits as you can get to fit into the "speaker bay." Additional length shouldn't hurt the FDD cable, it makes up the center section of the "SCSI" ribbon cable, doing double duty as alternate ground lines.

Haven't got the stuff handy ATM, going from the 3D model on the back of my eyelids.

 

[Themk]

Sigh, this hack is now in the wrong subforum :-/
 
Anyway, back to business.
 
Sounds good to make a Y cable. I'll look more at the machine later, it's not at my place yet. The "speaker bay" sounds lovely! The HDD I would use has a jumper for active termination, so it would be no biggie to enable that.
 
The guys over at the 'fritter have hacked A/UX on to the Quadra 650, so I am hoping that a similar procedure will get it up and running on the Quadra 638CD (performa 638CD started life with 33MHz LC CPU, gonna get 40MHz full 040; I think that qualifies it as a Quadra)

 

[Trash80toHP_Mini]

Electronically controlled sort of "active" as in just as much as needed when needed termination. Interested in the drive details if it has that capability.

 

[Themk]

Nah, I think its just your bog standard active SCSI termination, but enable able by flipping a jumper.

it is an IBM Ultrastar 2XP. DCHS-04U 4.5GB. Nice SCSI drive. 7200RPM, and fast. No mac can take advantage of how fast the drive is though, but the random read performance makes for a very snappy system.

 

[Themk]

Did some more looking around, I think I can run a multi-ended cable, have one end go back to the logic board, one end connect the CD-ROM drive, and then the last end go to my HDD, and then I'll terminate at the HDD (thinking I might also have to stick a terminator on the external port?). Now, I wonder if A/UX can be hacked to work with IDE (not likely). NetBSD supports IDE though, so if you just want a Unix on your 630, you don't have to do this SCSI hack. It's only if you want to run A/UX that you have to do a SCSI hack. I think if you want any Unix to run (I know NetBSD requires this), you need to have a full 68040. It isn't difficult to "quadra-fy" your LC/Performa version, just you need to know about it.

 

[Trash80toHP_Mini]

Quadra 630 is a bit on the quirky side. Its revolutionary architecture all but certainly makes it incompatible with A/UX.

 

[Themk]

At least its not a AV series machine. I still have some hope for this. It is going to require some hacking, but hopefully it works in the end. I'm hoping that the architecture is close enough to the 610 and the 650 architecture, rather than the AV architecture (though I realize in the timeline, this comes after the AV machines).

Also, I am aware of some of the differences, but what specifically makes it have a "revolutionary architecture"? (Isn't it also the last 68k based mac too?)

Now a slightly off topic question, I wonder what happens if you install a Quadra AV rom in to this machine. That would be cool if that worked, as I like the 'bong' startup chime introduced with the AV ROMs. (of course after you do that any hope of running A/UX goes out the window)

 

[Trash80toHP_Mini]

You'd break the already half assed/half borked IDE implementation for sure.

Interesting that this came up. I just started a rant discussion about Apple peripheral implementations and their habit of breaking industry standards by invariably going the way of the infinite loopiness. Did they ever even crack the book on IEEE Standards?

 

[Themk]

In the end, I'm not sure how much cheaper ATA ended up being for Apple. After all, they still included a full SCSI bus, with an internal connection for the CD-ROM drive too! (Got to solder a ROMSIMM slot to the motherboard, and shove a 840av flashed ROMSIMM into it.)

 

[Trash80toHP_Mini]

Need to set up a definitive benchmarking regime for a controlled test between 630 IDE and its SCSI implementation. I don't think it was any slower than the Mac's pathetic SCSI throughput. Touting SCSI as FAST in the fanboy wars or calling IDE "cheap" with the inference that it was s-l-o-w in the magazines was ludicrous. SCSI was FAST in workstation implementations and s-l-o-w on Macs.

All I know was that the Quadra 630 got a HUGE IDE drive transplant for a very reasonable price, I wasn't doing anything where disk was much of a limiting factor, money was.

 

[Themk]

I think I read a benchmark from LEM saying that the IDE on the 630 was no slower than SCSI on a Quadra 650. (Infact the IDE beat the SCSI in a couple tests!) I think the main point of that benchmark wasn't to methodically document its speed, but to rather debunk the myth that IDE was slower than SCSI.

53C94 is used in Q650 I believe. I gotta pop out the logic board and check to see what is on-board the 630. Also, the Quadra 630 supports PIO Mode 2 I believe, which is speced at 8.3 MB/sec, now while you won't be going that fast on a Q630 most likely, that would suggest that IDE is at least as fast as SCSI, even SCSI in a Quadra 950!

 

[Themk]

SCSI was FAST in workstation implementations and s-l-o-w on Macs.

the aging 53[C]80 controller needed to die sooner than it did with macs. Like you say, the SCSI performance on macs is nothing to write home about. Another thing to note is that controller uses an 8-bit data bus. Which means that on otherwise 32-bit machines, the bus could only transfer 8 bits of data at a time to the SCSI controller!

 

[Themk]

All I know was that the Quadra 630 got a HUGE IDE drive transplant for a very reasonable price, I wasn't doing anything where disk was much of a limiting factor, money was.

I think the ATA is to an advantage here. I have so many old ATA drives laying around, I am just going to shove a large-ish 7200RPM drive in there, and I will be golden. You could even use those cheap, (and ubiquitous) IDE to CF adaptors, and pop in an industrial CF card for some solid-state action! It would be even cheaper than SCSI2SD for possibly even greater performance!

 

[Compgeke]

Need to set up a definitive benchmarking regime for a controlled test between 630 IDE and its SCSI implementation. I don't think it was any slower than the Mac's pathetic SCSI throughput.

I actually did this kind of testing on the Powermac 6400. The results were the fastest drive was a 7.2k IBM Deskstar 60 gig hard drive, IDE. The SCSI itself wasn't great, kept about on par with the IDE bus but it's a terrible implementation on the 6400 (and older). It gets its ass kicked by my Supermac S900 with its onboard SCSI and let's just ignore the 9600 with the ATTO Ultra 160 card. I'll have to see if I can dig up the results somewhere, I used to have some graphs and stuff made.