[Coco] Tandy Assembly Exhibit: CocoMEM

[Brett Gordon]

1+ on mni - would be much more practicable. I forget Jim's board is a gimme
wedge.  is the mni routed through the gimme by chance?  Being able to mask
the firq in user context would be defeating.

On Oct 12, 2017 10:40 AM, "William Astle" <lost at l-w.ca> wrote:

> I suspect a lot of "advanced" OS9 programs will fail under proper memory
> protection. Some of the descriptions of "clever" techniques I've heard over
> the years lead me to suspect all manner of things that really aren't kosher
> being (ab)used.
>
> Speaking with my OS development hat on, I would much prefer an NMI on a
> "segfault" over FIRQ or IRQ.[1] That way a program can't mask it, even
> temporarily, by disabling interrupts. That will make it a *lot* easier to
> identify the source of the fault in most poorly written programs since it
> will always occur immediately after the instruction that triggered it
> finishes, at least if I have my facts on the 6809 straight. Also, the NMI
> is edge triggered so you wouldn't have to maintain an interrupt state
> anywhere once it fires.
>
> To head off the primary objection: this doesn't need to conflict with the
> FDC's use of the NMI. One could simply decide that an NMI occurring in
> "system  mode" when an FDC read/write loop is active is an FDC interrupt
> and anything else is a protection fault. The coding for that isn't that
> difficult (software wise).[3]
>
> [1] Actually, I would much prefer something more integrated into the CPU
> but that isn't going to happen without replacing the CPU with something
> completely redesigned. Definitely not practicable[2] for a memory board.
>
> [2] Cool word, practicable. Let's call that the word of the day. :)
>
> [3] Well, no more difficult than getting user<->system IRQ handling
> correct, anyway.
>
> On 2017-10-12 08:14 AM, Brett Gordon wrote:
>
>> Cool beans!  A mmu with read/write protection (when exploited) should make
>> for some interesting times.  I wonder how many poorly coded nitros9 (and
>> fuzix) proggies will seg fault :)  I imagine a segfault triggers a firq
>> (cart) then?
>>
>> brett
>>
>> On Oct 11, 2017 10:38 PM, "RETRO Innovations" <go4retro at go4retro.com>
>> wrote:
>>
>> On 10/6/2017 11:00 PM, camillus gmail wrote:
>>>
>>> Hi Jim,
>>>>
>>>> Do you except preorders?
>>>>
>>>> I'm in for the 32MB @ $24 ( is this the total cost or just the mem
>>>> chips?)
>>>>
>>>> It's just memory chip cost, not total unit cost.
>>>
>>> Let me finish getting OS9 running (close, just need to verify >2MB
>>> support), clean up the Verilog, and price out the unit
>>>
>>> Jim
>>>
>>>
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>>>
>>
>
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