You won't find any useful information in the PM7500...What would be nice is if some of you out there could do the following: Open up your retro-mac, locate the SCSI controller chip and list the chip info on top. We all know that the NCR/Zilog 53C80 is common amongst most 68k Macs, but I'm not sure what type of chip was used on most SCSI only based PPC Macs (pre-G3). I'll check my PM7500 and see what it is. Although, I don't care much for mine, since I just use a PCI Adaptec AHA-2940-U2B card and an 80 GB U160 LVD/SE HDD.
73s de Phreakout. :rambo:
I'm not sure when Apple made the switch, but at some point they went from the 53C80 to the 53C96. Most of the Quadras seem to have a 53C96. I asked and someone wrote that the firmware for the 53C96 is fairly different from that needed for the 53C80. Different register addresses and funtions I guess. I've never looked into it myself.
The Q660AV and Q840AV do not have a distinct SCSI chip. They use the AMD AM79C950K. That is code named CURIO by Apple. It is a combination ethernet, serial port, SCSI chip. It basically combines the ethernet MAC, 85C30 serial chip and the 53C96 or 53C94 SCSI chip into one component. I have never found a datasheet for it.
The NuBus PowerMacs contain the CURIO chip. The PM8100 uses a NCR/SYMBIOS/LSI LOGIC 53CF96 for its second Fast (10 MBPS) SCSI bus. Note the 'CF' in the part number as opposed to 'C'.
The PCI Power Macs still use the CURIO chip for the slow internal/external SCSI bus, but they now use a custom Apple chip for the Fast internal SCSI bus. The code name for that custom chip was MESH, but I suspect that it is just the IP for the 53CF96 put onto silicon under Apple's name. I'm not certain of that, but it seems a fair bet. They already had the code to support the 53CF96 in the 8100. Why develop a different custom chip for the PMx500 family?
After that, while SCSI was still around, it was usually integrated into a larger chip.
The 53CF96 is hard to find and usually expensive when available. Still, it would be interesting to replace the drivers in ROM for the 53C96 with the drivers for the 53CF96, do the chip swap on the logic board (Quadras, I guess) and see if you can double the SCSI performance.
If doing that, I would start by looking in the ROM of the 8100, because it needs to have drivers for both the CURIO's 53C94/6 and the 53CF96. A comparison of the two might be informative. Unfortunately, they may also be in PPC code instead of 68K code. Still, one could compare the 8100 CURIO 53C94/6 driver with the Q840AV CURIO 53C94/6 driver for reference.
That sounds like a lot of work for a not very big improvement in storage performance.