mac portable accelerator

[techknight]

I touched on this subject awhile back, but now I am thinking about it and going forward with it.

The ram card was a successful failure, it worked great and I sold quite a few but interest dropped off quickly, and ebay was not getting any more interest. There are still a few I might assemble, but ultimately with little demand i scrapped the project, and will likely come to a close. My thoughts on that is probably that most portables come with at least a 1 to 3MB Ram card already which is plenty for the machine. But I digress...

So this is my next idea. Thoughts? As far as I am aware, there are no accelerators that exist for this machine. And I want to be able to run a 68020/68030+ just because I can. 

This is going to be a large project with many roadblocks I am sure. One being the machine isnt 32-bit clean of course, and I dont know how mode32 is going to act because I am sure the machine is going to return a gestalt that isnt like anything thats ever been seen. lol. 

For now, i think it will remain DelcROM-Less and simply take over the 68000 as a bus master. So without ROM, or drivers, itll appear as a 68020, and probably will not see the FPU without some sort of a patch to tell the OS that an FPU is present. 

This processor upgrade will probably over-tax the internal 5V regulator, but I have that covered. the full battery voltage I think is present on the PDS, so I will likely use an on-board switching buck regulator to power this card outside of the main system power. 

 

[trag]

The biggest obstacle I see is that the cost of 68030 chips faster than 16MHz has been rising the last few years.   Although, there is a lot of ten 40MHz 68030s for $150 available at the moment.    Many others (singletons) are listed in the $30 - $50 range.

In any case, the supply is not reliable, but for the volumes you're likely looking at, that probably doesn't matter.

 

[Brooklyn]

I like the idea a lot, I think the market will be limited similar to the RAM card, not many people have a portable, and some people like to keep them original.  

If you can use lessons learned here to design an accelerator to drop in to the SE/30 PDS...  

 

[techknight]

I am just going to make a couple one-off adapters just to have. 

 

[IPalindromeI]

IMHO, this needs to be documented for the future. This is what the wiki would be great for!

 

[CelGen]

This sounds like it would destroy the battery life of the machine. It could barely handle a hard disk or an ADB mouse. There's no way you can get away with an 030 accelerator.

 

[unity]

Was not one theory to upgrade the hard drive to an SD drive. This would free up power for the accelerator. In fact I think one suggestion was to run power to the card via a y-splitter for the SD drive. It would be a weird work around, but it would still be plug and play.

 

[TheWhiteFalcon]

There's also the fact that it's not exactly a laptop as is...

 

[techknight]

Yea, theres alot of things to consider. Which is why its in the discussion/brainstorm phase. Most accelerators were designed back in the day with PAL/GAL logic, and those things were massive power hogs. 

Has anyone here taken temp readings off the SE/30 PAL ICs? Yea..... BTW the SE/30 logic board by itself pull around 1.75 to 1.85 Amps on the 5V Rail when its running. Yes, i know this. lol. 

Nowadays, its all CPLD/FPGA so it should consume alot less, but of course the processor will consume a fair bit. How much? I dont know, I will have to look at the datasheet.

As far as speed is concerned, it might be cheaper for me to go with a QFP package pulled from junk logic boards. 

 

[unity]

Well I have a possible NOS Portable mobo coming from a member here. Odds are its still dead, even if NOS. But it may finally provide a base to get a working re-cap. If she boots, I will want a memory card for sure. If an accelerator comes from this, I would love one too. I am not too concerned about processors and such. I have a bunch of spares anyway and I bet some other members have extras like me. So dont let that small point hold you back. You could probably supply then loaded or not.

 

[techknight]

Well, theres multiple ways I can go about it. 

As far as clock speed is controlled, I will likely use an ICS511 which I have in the past, its a jumper-adjustable PLL clock multiplier. So I can 1.5X or 2X, or etc the base system clock which is 16Mhz

but also include a jumper to run at 16mhz, or use an external crystal. But I know for a fact I have to use and/nor/flipflop gates to sync up with the 16mhz clock due to the VPA/VMA/E synchro bus to talks to the SCC/VIA. 

I do need to figure out how DTACK is handled. I think its generated by the RAM controller instead of the GLU on the Backlit model. This is important because if I double the clock speed, that means there is going to be two wait states inserted for every single wait state on the bus, (Macintosh LC anyone?) and if DTACK comes too early then it may cause me issues with RAM accesses. Then again, since the macintosh will be treated as a 16-bit port to a 32-bit processor, its going to take two cycles for every 32-bit data transfer anyway. (again, Macintosh LC anyone?)

What would be awesome is if I can attach the 8MB of SRAM directly on the 030 CPU and make it 32-bit RAM instead of the 16-Bit RAM onboard. that would increase performance drastically, BUT the thing that gets in the way of this is the Overlay function. Somehow I would have to ignore the system board during RAM read/write accesses. But at the same time still follow the overlay during RESET

hmmmm soo many things. lol. 

 

[techknight]

the 68EC030 draws much less power, and is much cheaper. But... no MMU, so no virtual memory. Following the motorola application note for adapting a 68020/68030 in a 68000 system should make this fairly straight forward. 

 

[CC_333]

Can the MMU be somehow emulated by one of those microprocessor/CPLD things?

c

 

[techknight]

Well technically the entire 68030 and FPU and MMU can be emulated in a full scale FPGA, and it has been done in the Amiga world. But FPGA stuff is still kind of over my head at this point. I am just now getting to know CPLDs. 

 

[aplmak]

Techknight I'll buy one... I came thru on the RAM.. lol.. But I want one if you make em.... I could also give you some 030 processors for it... and co processors...  to cut your cost... I've got a strange ROM card for the portable now.. Similar to Hap's.. Says ESPIRIT Apple Confidential.. 

Matt

 

[CC_333]

Yeah, I understand.

What could be done is some sort of hybrid, where the discrete CPU is used, and an FPGA is installed with some super simple dummy code so the accelerator works as if the FPGA weren't there. This would allow you to get the basics working, and then as you learn more about programming the thing, you can use it to emulate anything else that might be wanted, such as an MMU or FPU (and any related GLU logic).

Or at least design the circuit with an FPGA in mind (with any necessary stuff needed to get it working electrically) so somebody (if not you) can add it later without a major redesign.

c

 

[bigmessowires]

Love it.

I was kind of thinking about making an accelerator board for the compact Macs, like the Plus and SE. Not that there weren't plenty of those around back in the day, but they're not exactly common now. And it would be fun to add modern goodies to it. If that interests you at all, I'd be happy to help, and I think there would be a much bigger market than for a Portable-specific accelerator. 

Either way, I think the only 68000-family CPU that's still in production is the 68SEC000, which goes up to 20 MHz. Digikey has the 16MHz version for about $15 if you're buying a few at once: http://www.digikey.com/product-detail/en/MC68SEC000AA16/MC68SEC000AA16-ND/954577

Beyond that, if you want 68K family, you'd probably have to use a Coldfire or Dragonball CPU. But I'm not sure those are still available either, and they're different enough that there might be software-level or ROM code incompatibilities.

Maybe you could find a box of old stock 68030's from one of the surplus parts warehouses or through octopart.com

 

[techknight]

Well, I think there is an open core/source project for FPGAs for at least a 68020 accelerator with FPU emulation as well. inside a single FPGA. 

That might be an option, although a bit over my skill level. I dont mind making an accelerator or joining in for other machines as long as I can backtrack and apply it to a new PCB to support the portable. 

 

[techknight]

Thinking about using an XC95144XL because of its high pin-count. This will allow me to route the entire address bus plus all the PDS signalling, as well as all the special control and handshake lines from the 68030 as well. 

This gives me room for experimentation of the logic without the need of re-spinning the board. I think these CPLDs have enough drive current to manipulate the bus directly using internal buffers. Save costs, but scouring the datasheet to be sure.