Found a Neat Mod From Back in The Day in My 128k

[Trash80toG4]

Yep, did just that. When I got a NewLife board for my 512K I found its CPU package was Killy Klip incompatible so I got a dirt cheap 128K board from Shreve to keep the 512K safe from harm. Soldered it up and chickened out. Took it over to my buddies at Tekserve to test it out. They gave it back with 2.5MB installed, saying it was a very interesting board. Had provision for TTL video out, which was a big reason for buying it. They never got that up and running before going kaput.

 

[retr01]

If you want a modern replacement, @Stephen made this: https://github.com/Stephen-Arsenault/CloneyClip

Thank you, @Kai Robinson! I bookmarked it. Maybe one day, my collection will grow to include a Mac 128k or 512k.

 

[retr01]

I got a dirt cheap 128K board from Shreve

Shreve Systems in Louisana? Wow. Too bad that place is gone.

 

[Trash80toG4]

Apple I's $666.66 price tag in 1976 is $3,471.68 today, a whopping 420.76% jump! Much more than the Mac IIfx's 126.71% jump.

1977 brought Carter-StagFlation-Oil Embargoes etc. I wonder if much of that differential happened across just the first few of the intervening 13 Years? There's little comparison between 6502/68K periods and today that makes much sense.

@Stephen have you refined your design since we last talked about it at the MLA? ISTR you saying it needed some?

 

[trag]

Yep, did just that. When I got a NewLife board for my 512K I found its CPU package was Killy Klip incompatible

You had the ceramic package 68000 on your 512K?

The ceramic package is flatter than the plastic package and doesn't fit the Killy clip properly.

 

[mg.man]

Apols for being late to this thread, but I too had a surprise a while back when I picked up what was supposed to be an 'original' 128k... What I discovered when I opened it up was the following...

Yep... that's an original 128k 'board, but "fattened" out to a full 2Mb!! And... it still works!

This represents a brief period of time when eager enthusiasts were willing to "risk it all" to reach the dream they were sold with the 128k (and 512k).

Completely agree!

 

[retr01]

I have been thinking about the 68000 capability to address up to 16 MB of RAM and the Mac 128k and 512k. Now that there were add-on cards back in the day to slap on the mobo, it shows how careless Apple was back then.

I am sure you wonder why Apple was careless with the 128k and 512k. Apple did NOT allow connecting address lines from the 32-bit 68000 to address 0 to 23 lines (24-bit) out of the processor to the memory. Yet, those small companies connected to more address lines and allowed more memory.

So, why just 2 MB? Why not more? I know it was expensive back then for RAM, but did the add-on cards already have full 0 to 23 lines connected? Are they capable of maxing out of 16 MB despite what they say on paper?

My question is, HOW MANY lines are running from the 68000 to memory?

• Stock 128k / 512k boards - 19 lines?
• Perspect Systems Inc
• and others?

Or do those add-on boards use the memory paging trick, nothing fancy like connecting to more address lines?

 

[mg.man]

So, why just 2 MB? Why not more?

No expert here, but I'm pretty sure ROM and maybe I/O (?) is mapped into the 16Mb space. I've read somewhere that this is why the compacts up to the SE were limited to 4Mb max.

 

[mg.man]

...it shows how careless Apple was back then.

I'm not sure it was just that... but also an acute shortage of DRAM chips. For example, I have a genuine Apple replacement (box, docs and all!) IIgs motherboard that came with the attached advisory. There's no date, but it does make you wonder what might have been gobbling up the DRAM supply...

 

[retr01]

No expert here, but I'm pretty sure ROM and maybe I/O (?) is mapped into the 16Mb space. I've read somewhere that this is why the compacts up to the SE were limited to 4Mb max.

In the Plus and SE, Apple only connected 22 lines out of 24 out of the 68000. That meant the Plus and SE could only address 2 to the 22nd power bytes, which is 4,194,304 or 4,096 kilobytes, equaling 4 megabytes. The 68000 processor connects to the 24 lines, translating to 16,777,216 bytes or 16 megabytes.

Memory mapping by software in the ROM and operating system is secondary to what the hardware can and could further limit. I did read somewhere that Apple's System OS did map memory that only this much was usable for the system and programs, leaving any other space for some other functions.

 

[retr01]

I'm not sure it was just that... but also an acute shortage of DRAM chips. For example, I have a genuine Apple replacement (box, docs and all!) IIgs motherboard that came with the attached advisory.

Yeah, it makes sense. However, Apple was kind enough to up the memory because those chips were available (and it was probably cheaper due to supply constraints). I have displayed the paper for those who do not want to download the PDF and for preservation efforts.

There's no date, but it does make you wonder what might have been gobbling up the DRAM supply...

Around the early 1990s, some chip shortages, including the 256k DRAM chips.

 

[Trash80toG4]

You had the ceramic package 68000 on your 512K?

The ceramic package is flatter than the plastic package and doesn't fit the Killy clip properly.

Ancient history, but yeah, 128K board came in with the same package type so did the soldered header install. Stock 128K boards were all but useless electronics waste back then and don't get any better when downgraded to pseudo-original status now. If it's been upgraded its a Mac, if it's at 128K it's an all but useless RoadApple. With an external FDD you can get some stuff done on a 512K. 128K=Bopkes

edit: don't bother looking it up, bopkes is Yiddish for goat droppings = utterly devoid of worth