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Looking to replace my onboard SCSI chip and have a question.
- Thread starter Verault
- Start date
aperezbios
Well-known member
While I can't tell you what the -40 is (speed rating possibly?), I am very confident that you will be able to use the -40 variant without issue.
The datasheet (here) describes the 53C80-40 as being a CMOS replacement for the original NMOS 5380, but also describes the 53C80 as being functionally equivalent to the 5380.... So that makes all 3 functionally equivalent it seems....
It's not entirely clear from the datasheet, but I would be very surprised if the 53C80 and 53C80-40 where not cross compatible
It's not entirely clear from the datasheet, but I would be very surprised if the 53C80 and 53C80-40 where not cross compatible
Verault
Well-known member
Might not be compatible after all: https://68kmla.org/bb/index.php?thr...-plugged-into-the-scsi-bus.39144/#post-423125
SuperSVGA
Well-known member
You could try ZiLOG's version of it (https://www.mouser.com/ProductDetail/ZiLOG/Z53C8003VSG?qs=FsLZlD%2B%2Bd9cJEZW2nIhyXQ==), the pinout is the same as the 53C80 and it states it is compatible with the 5380 standard, so I would say there's a high chance of it working.
Edit: You could also try Utsource (https://www.utsource.net/itm/p/765398.html)
Edit: You could also try Utsource (https://www.utsource.net/itm/p/765398.html)
Kinda embarrassed I missed that on the datasheet!
aperezbios
Well-known member
Sure enough, the 53C80 and 5380 don't even have the same pin count. See https://bitsavers.computerhistory.o...0_SCSI_Interface_Chip_Design_Manual_Mar86.pdf
Page 3 of that PDF says the following: "A CMOS version of the NCR 5380, the NCR S3C80 is available in a 44·pin PLCC or a 48·pin DIP. Refer to Appendix A5 for information on the NCR 53C80."
Page 54 states, "The NCR 53C80 CMOS SCSI interface device is functionally equivalent to the NMOS NCR 5380 device. However, this chip does not offer pin compatibility. CMOS and NMOS are entirely different processes with inherently different device characteristics. All CMOS devices are designed to prohibit a condition commonly referred to as 'latch-up'. When the high current 48 mA drivers in the NCR 53C80 switch, noise level is sufficiently high, the output drivers become more prone to 'latch-up'. Therefore, for the CMOS design, pin compatibility has been foresaken for reliabilty. Four additional ground lines have been added to increase design stability. Having additional ground signals also allows the output buffers to switch more quickly, creating the added benefit of a faster design. This does not imply that the NMOS device is marginal in any respect."
Page 3 of that PDF says the following: "A CMOS version of the NCR 5380, the NCR S3C80 is available in a 44·pin PLCC or a 48·pin DIP. Refer to Appendix A5 for information on the NCR 53C80."
Page 54 states, "The NCR 53C80 CMOS SCSI interface device is functionally equivalent to the NMOS NCR 5380 device. However, this chip does not offer pin compatibility. CMOS and NMOS are entirely different processes with inherently different device characteristics. All CMOS devices are designed to prohibit a condition commonly referred to as 'latch-up'. When the high current 48 mA drivers in the NCR 53C80 switch, noise level is sufficiently high, the output drivers become more prone to 'latch-up'. Therefore, for the CMOS design, pin compatibility has been foresaken for reliabilty. Four additional ground lines have been added to increase design stability. Having additional ground signals also allows the output buffers to switch more quickly, creating the added benefit of a faster design. This does not imply that the NMOS device is marginal in any respect."
Franklinstein
Well-known member
From what it appears, the 53C80 chips should be identical regardless of any suffixes since they're the same CMOS-based 5380 core. I mean if you're stuffing it into an SE/30 it won't be getting any signals faster than 16MHz anyway (and only 8MHz in a Classic). The other thread referenced above seems to have had problems greater than a questionable SCSI chip so I'm not sure it adds any value to the discussion.
I think the original confusion was in compatibility with the original 5380 and the updated 53C80 design, and apparently there isn't any owing to a different pinout (and likely different voltages and other signals owing to the CMOS design).
Short answer: all NCR 53C80s should be compatible with one another, including Zilog (and other) clones, but in a very high-speed application you may need to look for one with a particular suffix.
I think the original confusion was in compatibility with the original 5380 and the updated 53C80 design, and apparently there isn't any owing to a different pinout (and likely different voltages and other signals owing to the CMOS design).
Short answer: all NCR 53C80s should be compatible with one another, including Zilog (and other) clones, but in a very high-speed application you may need to look for one with a particular suffix.
Verault
Well-known member
You can see what happened on this thread: https://68kmla.org/bb/index.php?threads/macintosh-classic-stalls-booting-when-
It didnt go well and I got burnt out so I put it back in storage to try and tackle another day and move on to other projects..
But I can say, to this date.. Never found a mac classic that could be saved. I would avoid them like the plague.
It didnt go well and I got burnt out so I put it back in storage to try and tackle another day and move on to other projects..
But I can say, to this date.. Never found a mac classic that could be saved. I would avoid them like the plague.
JT737
Well-known member
@Franklinstein -Thanks! Yea, my biggest concern was the pinout compatibility. I think that I found the same eBay auction that Verault did- some guy selling the NCR 5380 -40 SCSI chips. But I also found someone selling L5380JC-2 chips made by Logic Devices, and was unsure if those would work.
In the end, I bought a few LSI SYMBIOS 53C80S chips.....hopefully they will do the job.
@Verault - The Classic is definitely a tough computer to bring back from the dead. I have one that I recapped and repaired four traces on-and it worked well for a while! That is until I recently tried to start it up.....haven't bothered to look at it yet.
In the end, I bought a few LSI SYMBIOS 53C80S chips.....hopefully they will do the job.
@Verault - The Classic is definitely a tough computer to bring back from the dead. I have one that I recapped and repaired four traces on-and it worked well for a while! That is until I recently tried to start it up.....haven't bothered to look at it yet.
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