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nubus scsi card any benefit?
- Thread starter jholt5638
- Start date
Trash80toHP_Mini
NIGHT STALKER
Until the Q950 and Q840AV, SCSI performance on the Mac was uniformly pathetic and only achieved "barely" acceptable in those models. I'd think even a standard SCSI card would blow the doors off the crappy implementation of SCSI on the Mac, so it certainly can't hurt to try!
Which Mac?
Is the card Fast/Narrow SCSI II or Fast/Wide SCSI II like the JackHammer?
Which Mac?
Is the card Fast/Narrow SCSI II or Fast/Wide SCSI II like the JackHammer?
Trash80toHP_Mini
NIGHT STALKER
Doesn't sound like a SCSI card part number, especially from NatInt. They made Digital I/O cards and the like for the Mac. If it's an IDC50M header connector like a MoBo or internal SCSI device that's sticking out the backplane, it's definitely not a SCSI card.
NatInt used that connector, but it's for hooking up all sort of lab equipment/sampling and digitizing analog inputs etc.
edit:
Bingo!
http://www.ni.com/pdf/manuals/320640.pdf
http://www.datasheetarchive.com/NB-MIO-16X/Datasheets-UD1/DSAUD003430.html
Sounds like a typo or simple mistake substituting an "M" for the "N" for the NuBus designator, but "MIO" would be NatInt's Model Number terminology for a Multifunction I/O Card.
NatInt used that connector, but it's for hooking up all sort of lab equipment/sampling and digitizing analog inputs etc.
edit:
Bingo!
http://www.ni.com/pdf/manuals/320640.pdf
http://www.datasheetarchive.com/NB-MIO-16X/Datasheets-UD1/DSAUD003430.html
Sounds like a typo or simple mistake substituting an "M" for the "N" for the NuBus designator, but "MIO" would be NatInt's Model Number terminology for a Multifunction I/O Card.
Last edited by a moderator:
Paralel
Well-known member
Here are the official SCSI transfer rates for given Mac models according to Apple:
http://support.apple.com/kb/TA29470?viewlocale=en_US
Most of them really suck, of course, since many of them are based on the 53C80, this is no surprise.
Also, for the PB 500 series, when it says "Custom IC" they really mean it's a 85C80 derivative smashed together with the serial controller into one chip, probably to save space/money/etc...
For the PB 500 series, if one can get a Rev C card cage, your system will be far better off booting from a decent CF card than the internal SCSI Bus.
http://support.apple.com/kb/TA29470?viewlocale=en_US
Most of them really suck, of course, since many of them are based on the 53C80, this is no surprise.
Also, for the PB 500 series, when it says "Custom IC" they really mean it's a 85C80 derivative smashed together with the serial controller into one chip, probably to save space/money/etc...
For the PB 500 series, if one can get a Rev C card cage, your system will be far better off booting from a decent CF card than the internal SCSI Bus.
Last edited by a moderator:
Interestingly, the tech note doesn't mention the second Fast Internal Bus in the 8100. Only the external/internal bus is mentioned. The "custom" chip starting with the AV Quadras and running through the NuBus PowerMacs and on into the PCI PowerMacs is the AMD AM79C950 which Apple called CURIO. It containsthe equivalent of a 53C94, an 85C30 and some kind of ethernet MAC. It was a custom job from AMD for Apple and the datasheet is not available.
The 8100 was the first Mac with a Fast SCSI bus in addition to the regular slow bus. While the Q900/950 had dual SCSI busses, they were both based on the 53c96. The 8100 used the 53CF96 for it's internal Fast bus.
After the 8100, Apple switched to their "MESH" chip for the internal Fast SCSI busses in the PCI PowerMacs. I suspect, but don't know, that MESH is really just a licensed 53CF96. One of these days, maybe I'll try replacing one with the other to prove or disprove it.
Elfen
Well-known member
In discussing this with dad, is it possible to replace the 53C96 chip with the 53CF96 and automatically improve performance? Or does the ROM has something to say about the speed limits the buss can have? He has been wondering for months, what if he replaced the old slow 5380 from the old Macs with a faster chip like the 53C96. Pin to pin compatibility would be an issue but an adapter could fix that. But would ROM slow down the data transfers?
In the 8Bit days, dad has swapped out older 6502s from various machines with faster ones and managed to get some improvement out of the old machine.
Trag,
This is super interesting, but not surprising. You're not the first to have such musings! If one searches the mailing lists of the netbsd project and linux kerel there was much speculation about it. Since the two chips are so similar in package and driver spec, I'd say your hunch is right on the money. The MESH chip is likely a licensed and improved version of the earlier chip.
//wthww
This is super interesting, but not surprising. You're not the first to have such musings! If one searches the mailing lists of the netbsd project and linux kerel there was much speculation about it. Since the two chips are so similar in package and driver spec, I'd say your hunch is right on the money. The MESH chip is likely a licensed and improved version of the earlier chip.
//wthww
ArmorAlley
Well-known member
jholt5638: Will switching to nubus scsi controller give any boost over the onboard one?
In my experience, the advantage of a NuBus SCSI card is firstly to give access to the very (well, relatively very) new SCA drives that are very large, quiet, fast and hot. As has often been discussed in these fora, many SCA drives will not work on an 8-bit SCSI bus. All Mac internal SCSI-buses are 8-bit. LVD-SCSI is 16-bit and it would almost usually allow the use of 146GB SCA drives. Such a drive is useful in Quadras and above, which can run Mac OS 8.1. Your Q700 mightn't be able to read a 127GB volume quickly, but with 8.1 it *will* be able to do it.
The second advantage is speed. With the newer drives with their larger caches and faster spin times, 8-bit SCSI can access only so much data per second. 16-bit SCSI can access much more. Whether that is useful or not is another matter.
As a matter of reference, I ran Speedometer 4.02 on my IIfx. The rating for disk for the 50-pin HD in there at the time was 1.3 while the equivalent rating for a SCA-drive with 80-pin-to-68-pin adapter connected to a NuBus FWB JackHammer was 2.8
In my experience, the advantage of a NuBus SCSI card is firstly to give access to the very (well, relatively very) new SCA drives that are very large, quiet, fast and hot. As has often been discussed in these fora, many SCA drives will not work on an 8-bit SCSI bus. All Mac internal SCSI-buses are 8-bit. LVD-SCSI is 16-bit and it would almost usually allow the use of 146GB SCA drives. Such a drive is useful in Quadras and above, which can run Mac OS 8.1. Your Q700 mightn't be able to read a 127GB volume quickly, but with 8.1 it *will* be able to do it.
The second advantage is speed. With the newer drives with their larger caches and faster spin times, 8-bit SCSI can access only so much data per second. 16-bit SCSI can access much more. Whether that is useful or not is another matter.
As a matter of reference, I ran Speedometer 4.02 on my IIfx. The rating for disk for the 50-pin HD in there at the time was 1.3 while the equivalent rating for a SCA-drive with 80-pin-to-68-pin adapter connected to a NuBus FWB JackHammer was 2.8
Trash80toHP_Mini
NIGHT STALKER
The FWB JackHammer ROCKS! I'ce got the PLI QuickSCSI NuBus card in the pet IIfx, never thought to test it against the JackHammer in the Radius 81/110 though.
Not sure I'd bother with it IRL because it likely (certainly?) requires NuBus 90 to give it free rein.
After the recap, gotta do time trials of both on both now!
Not sure I'd bother with it IRL because it likely (certainly?) requires NuBus 90 to give it free rein.
After the recap, gotta do time trials of both on both now!
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