Re: upgrading CBM-3040?

On Mon, Nov 13, 2017 at 8:14 PM, Mike Stein <mhs.stein@gmail.com> wrote:
>
> ----- Original Message -----
> From: "Francesco Messineo" <francesco.messineo@gmail.com>
> To: <cbm-hackers@musoftware.de>
> Sent: Monday, November 13, 2017 1:48 PM
> Subject: Re: upgrading CBM-3040?
>
>
>> On Mon, Nov 13, 2017 at 7:37 PM, Mike Stein <mhs.stein@gmail.com> wrote:
>>>
>>> ----- Original Message -----
>>> From: "Francesco Messineo" <francesco.messineo@gmail.com>
>>> To: <cbm-hackers@musoftware.de>
>>> Sent: Monday, November 13, 2017 11:33 AM
>>> Subject: Re: upgrading CBM-3040?
>>>
>>>
>>>> On Mon, Nov 13, 2017 at 3:17 PM, william degnan <billdegnan@gmail.com> wrote:
>>>>> Yes.  There was an upgrade kit.  If you can find the chips or steal them
>>>>> from a 4040 drive here is what I found:
>>>>>
>>>>> Replace the 6530 with the CBM chip 901466-04
>>>>> UL1 gets a 901468-12
>>>>> UJ1 gets a 901468-11  (take from 4040 UK1)
>>>>> UH1 gets a 901468-13
>>>>
>>>> ok, the last three chips can be 2532 EPROMs with the right content, no
>>>> problems here.
>>>> Looking at the schematics, it seems that the 6530's ROM is selected by
>>>> /RS0 only, so in theory, I could
>>>> make an adapter to tie /RS0 of the original 6530 high, and use the
>>>> select signal to enable another external EPROM for the new
>>>> code. The rest of the 6530 should continue to work as expected, am I right?
>>> ---
>>> Some drives use 2332s with an active-high chip enable and it looks like that's the case with the 2/3/4040 drives' CS2, so you might also have to add an inverter in order to use 2532s.
>>
>>
>> right.... clock phi2 from the 6502 (buffered) goes to pin21 of all the
>> ROMs. It prevents the ROMs to be selected during the low part of phi2.
>> Now I'm puzzled, what would drive the data bus during the low part of
>> phi2 that they had to prevent a possible bus conflict?
>>
>> Frank
> ---
> Isn't that when the 6504 takes control of the bus?

Ah yes, makes sense. I didn't notice that the two CPUs shared the data bus.
>
> m
>
>
>        Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list