DingusPPC: A more accurate PowerPC Mac emulator

[Arbee]

So, it's not DMA'd on the Q630, it's SCSI PIO <facepalm>

The only 68k Macs with DMA SCSI under Mac OS are the Quadra AVs. (IIfx has hardware for it but only A/UX uses it).

 

[croissantking]

I think there was, and all Apple did for the 6200/6300 was redesign the logic board such that it was built in.

Would the upgrade have actually been a 6200 board? (As opposed to a LCPDS 601 card)

A clue to this, I believe, is that the 630 and 6200 logic boards are interchangeable and will run in each other's chassis. I'm not sure if the 6300 LB would run properly in an unmodified 630 or 6200 chassis, but the later ones (6360, 6400, etc) almost certainly won't run properly without chassis mods.

The only issue with running 6360/6400/6500 etc boards in a 630 chassis is the lack of 3.3V from the PSU. A 6300 or 6320 board would drop into a 630/6200 with no problem.

 

[CC_333]

Would the upgrade have actually been a 6200 board? (As opposed to a LCPDS 601 card)

I'm not sure.

If not, what does a PPC upgrade for a 630 look like?

The only issue with running 6360/6400/6500 etc boards in a 630 chassis is the lack of 3.3V from the PSU. A 6300 or 6320 board would drop into a 630/6200 with no problem.

I see. I thought it was something along those lines, but I couldn't remember for sure (my knowledge is a bit rusty from having been on the sidelines for the better part of a decade (2019-ish to now-ish)).

c

 

[croissantking]

I'm not sure.

If not, what does a PPC upgrade for a 630 look like?

Question for the hive mind then, is there one?

 

[CC_333]

Question for the hive mind then, is there one?

Indeed.

A quick search uncovered this LEM article (take it with appropriately-sized gain of salt): https://lowendmac.com/2016/powerpc-601-cpu-upgrades-for-68040-macs-with-lc-pds/

If the article is correct (why wouldn't it be?), there apparently was an Apple Power Mac Processor Upgrade (APMPU for short) made by DayStar and featuring initially a 66 MHz PPC 601. DayStar also marketed the upgrade directly as the PowerCard 601, and later also released a 100 MHz version of it.

When DayStar went under, Sonnet took over the design and sold it as the Presto PPC.

Hopefully someone can confirm all this.

c

 

[Snial]

<snip> Apple Power Mac Processor Upgrade (APMPU for short) made by DayStar and featuring initially a 66 MHz PPC 601. <snip>

Hmmm. I guess the card came with a full GD emulator, 4MB PPC ROM?

 

[CC_333]

What's a GD emulator?

I'm pretty sure the 4 MB ROM is necessary for it to work, so it must have been included?

c

 

[croissantking]

What's a GD emulator?

I'm pretty sure the 4 MB ROM is necessary for it to work, so it must have been included?

c

Gary Davidian - the guy who wrote the 68k emulator

 

[Snial]

What's a GD emulator?

Cr CroissantKing’s reply.

I'm pretty sure the 4 MB ROM is necessary for it to work, so it must have been included?

Not necessarily. If the system boots from 68K, it’ll check for a PPC ROM, but it could be a minimal ROM. Then you could load the PPC ROM from disk, like a NewWorld Mac does, because you already have a CPU that can do that. Then juggle the (PPC) MMU tables so the ROM is in the right location, then jump to the right place in the PPC Rom, it’ll reboot and we’re in PPC mode.

I should clarify, I suspect these upgrade cards do actually have whole 4MB ROMs.

 

[trag]

The machines had what was essentially a 6100 ROM set on board, according to one of the Daystar support dudes I communicated with, way back when in the days when if you called for support, you might end up talking to one of the engineers. These outfits were small. Often just a couple of guys.

There were three basic types of PPC upgrade from Daystar. Ones targeted at the IIci cache connector (Turbo601), ones with the Quadra PDS connector, and ones with a 68040 PGA connector.

I don't think there was one for the Color Classic/LCII connector, but I could be mistaken. I did not know that the Value040 existed until I ended up with seven or eight of them.

In all cases, because they're based on the first revision of the 68K emulator included in the X100 ROMs, using Connectix's "Speed Doubler" will provide a substantial boost in performance for most tasks.

 

[powermax]

So, it's not DMA'd on the Q630, it's SCSI PIO <facepalm>.

No. Apple engineers call it pseudo-DMA. It's supposed to work like that: an I/O ASIC provides a special HW register whose content will be moved over the real DMA interface to/from the target device. In PowerMacs, it's mostly the Curio ASIC.
The I/O ASIC provides all required signals for the DMA interface, just like a real DMA engine.

Programmed I/O (PIO) is slightly different: it doesn't use DMA signals and it always transfers 8 bits at a time.

The AMIC ASIC in the Power Macintosh 6100 provides all three types of transfer interfaces: PIO (8-bit transfers), pseudo-DMA (16-bit transfers) and real DMA (bulk transfers). The former two are used by the ROM loader to locate and load the required device drivers that switch to real DMA.