[Coco] Tandy Assembly Exhibit: CocoMEM

[RETRO Innovations]

On 10/6/2017 6:40 AM, Francis Swygert wrote:
> Date: Thu, 5 Oct 2017 09:09:41 -0500
> From: RETRO Innovations <go4retro at go4retro.com>
>
> On 10/5/2017 6:14 AM, Francis Swygert wrote:
>> Just read your page on CoCoMEM -- impressive indeed! From what I read the memory is soldered to the board and you have been testing 4MB. I can't imagine really needing/using 4MB (well, could pre-load graphics/data for games, fetch from RAM instead of disk/storage as needed... might be faster.. and maybe the ubiquitous RAM drive...), but if you wanted more it would have to be soldered in as well. So one point... are there larger capacity chips that have the same pin-out as the ones used? if so, a simple socket might be the easy way to allow expanded memory -- would take up a lot less room than traditional SIMMs.  Frank Swygert
>>    Fix-It-Frank Handyman Service
>>    803-604-6548
>>
> Sadly, sockets are not available for the small IC packaging SRAM options
> utilize.  And, the packaging changes between sizes (2x2MB is what's on
> the board, while larger options require a different PCB footprint).
> ======================================
> That's what I was afraid of (no sockets or larger packaging). IMHO, the best thing to do is to consider just what more than 4MB would be used for. Even OS-9 has a practical limit as to what it can effectively use. Sure, you can have 20 windows open in memory, but 20 processes actually working would be impractical... maybe four doing something (but not much on a real 2 MHz CoCo3!). Probably four open and only two actually working (on in background, one in foreground) would be the practical limit. So other than storing data, what can the extra memory be used for? Gamers could speed things up by having graphic data loaded from the start, and of course a RAM disk for fast data access for something like a spread sheet (if anyone still does that with a physical CoCo3). But is more than 4MB really useful to all but a handful of people? If not, and I certainly can't see it, then 4MB is probably a good number. Of course it's like Gene said -- what's the cost difference for more? If only a few bucks for 8MB... But all the way to 32MB? I just don't see where it's useful -- beyond graphics screens for games. Then the game would have to be written to take advantage of the memory -- would run slow on a 512K machine, or not at all. There are existing 2MB upgrades though, so if it was compatible with those...  Lots to consider to make it practical!!
>   Frank Swygert
>   Fix-It-Frank Handyman Service
>   803-604-6548
>
Concerning Gene's question that you reiterate:

512kB = $3.41 base cost (@ 100 unit prices)

1MB = $3.66 base cost

2MB = $11.74 base cost (yep, I know...).  Better to do 1 x 1MB @ 7.32, 
but still too expensive

4MB = $4.63 base cost

8MB= $5.97 base cost


So, from a strictly financial perspective, there is little advantage to 
going below 8MB, and no value in doing 2M. You can save a bit and not 
affect the PCB footprint by designing for 4MB/8MB, as they use the same 
IC footprint, so I guess I could support those two sizes.  But, there's 
a cost to handling two variations of the board, and extra software to 
test, so I'd prefer not doing that.

I admit when I asked the question initially, I had not consulted the 
sales figures, but the refined question now would be:

You're getting 4 or 8MB.  Does anyone see value in doing more?  Paul 
planned on 16MB, so at least was considering things (maybe not realistic 
things, but...)

All that said, I'll probably design a 64MB board or two, just for me :-) 
Just for bragging rights

Jim



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