Difference between IDE controller on 1997 beige G3 and 1998 beige G3

[Phipli]

I see specific differences between first release and the enhanced model. However any further changes appear to to me to be component compatible builds to upgrade performance of what's called Rev.B. There are A/B/C ROMS with the latter likely required for making full use of the Rage II Pro Turbo, which I'm guessing is the same package as the more pedestrian variant on earlier Rev.B logic boards that are identical to what some are calling a Rev.C board?

No note of a third variant of the system board mentioned on everymac, just component upgrades?

Pro Turbo runs fine with a Rev A ROM - thats the Drivers job

 

[powermax]

Pro Turbo runs fine with a Rev A ROM - thats the Drivers job

All Beige G3 ROMs I've seen so far contain Open Firmware drivers as well as native drivers for soldered on-board ATI GPUs. Otherwise, those chips would not be recognized at all.

 

[trag]

Still looking for the delete button. POsted too soon.

 

[trag]

Do we need new ROM SIMMs for that or is it possible to reflash old ones?
BTW, I remember seeing a Wiki page with pinouts for various PowerMac ROM SIMMs.
It looks like the page has disappeared. I can't find it anymore.
IIRC, it was created by @trag but I'm not sure...

My ISP of 25 years shut down or will soon. File is now located here: http://sphinxgroup.org/Apple_pinouts/Firmware_Module_Pinout.txt

 

[Phipli]

My ISP of 25 years shut down or will soon. File is now located here: http://sphinxgroup.org/Apple_pinouts/Firmware_Module_Pinout.txt

@trag

Do you have a copy of your site for yourself? I just scraped it (hope you don't mind). I won't have anything that doesn't have public permissions, but I can share a copy with you if you want. It's a 1.1GB zip.

 

[trag]

@trag

Do you have a copy of your site for yourself? I just scraped it (hope you don't mind). I won't have anything that doesn't have public permissions, but I can share a copy with you if you want. It's a 1.1GB zip.

Thank you. I have a local copy, but that was a kind offer.

I'm not sure I would glorify my collection of files by calling it a "site". It's just stuff I've thrown up into on-line file space over the years for convenience as circumstances dictated.

 

[Phipli]

Thank you. I have a local copy, but that was a kind offer.

Excellent, I assumed you had, but wanted to be sure.

I'm not sure I would glorify my collection of files by calling it a "site". It's just stuff I've thrown up into on-line file space over the years for convenience as circumstances dictated.

My site is similar. It's an Iceberg - 90% under the surface. Little bit of UI and lots of folders only accessed by direct links

 

[powermax]

Note that the ATA implimentation on the Beige G3 was pretty funky at the ROM level. The machine suffered from the same Int 13h 8.4GB boot barrier despite that problem being specific to the PC BIOS!

You're right with that 8.4GB barrier on Beiges. I did some research on this issue. Here my results:

• both Beige ROM revisions I have dumps for contain ATALOAD driver. This is actually the same old code as found in some Power Macintoshes and Power Books with default IDE support like PM 5200 or PB 1400c.
• ATALOAD uses the old fashioned CHS {cylinder, head, sector} addressing for disk accesses.
• ATALOAD issues IDENTIFY DRIVE command to the drive, then uses the values in words 1, 3 and 6 of the returned data as disk geometry for the consecutive disk accesses.

The last fact is the actual culprit because the drives larger than 8.4GB should report their default geometry as having 16,383 cylinders, 16 heads and 63 sectors per track in the words 1, 3 and 6 respectively. That gives the maximum capacity of about 8,1GB (binary) or 8.455GB (decimal). Reporting such a limited capacity in the deprecated variables allows them to work with legacy operating systems like DOS or Windows 95.

The 8.4GB barrier on Macs is therefore caused by relying on deprecated information in the drive identification data. I don't know why Apple kept that old code for that long. At the times Beige G3 machines were released the majority of the ATA drives could use LBA addressing instead of CHS. SCSI uses LBA addressing from the very beginning.

 

[NJRoadfan]

The beige G3 came out in 1997, a year before the Int 13h extensions became available on the PC, although this really didn't apply to Macs. Going by the presence of the IDENTIFY DRIVE command and PIO4 transfer rates on the circa 1994 Performa 630 series, one could assume the original code targeted the ATA-2 standard. This fully supported direct 28-bit LBA access to drives, but Apple clearly didn't use it in their ROM driver. The now legacy CHS addressing was limited to 24bits, thus the silly 8.4GB limit.