[Coco] Replacing Dynamic RAM with Static RAM

Fri Jun 11 20:37:07 EDT 2010

J&R,
Whats your name btw.

I have circuit boards for another project that should have all the
connectivity and stuff needed to implement this.  I just don't know
what the logic design is.  So, we could avoid PCB costs too, at least
for low volumes.

I'm also quite good at the soldering part.

Steve

On Fri, Jun 11, 2010 at 4:40 PM,  <sales at gimechip.com> wrote:
> Absolutely - putting the logic into a CPLD would be ideal. The ideal latch
> would be a 9-bit non-transparent if you decide to put the design into a CPLD
> - you can use the schematic entry and let the development suite generate the
> HDL's. I'll send you all of the info when I get it together, if you want -
> just let me know - I love working out this stuff. It's like a puzzle, only
> way better :-)
> J&R
> ----- Original Message ----- From: "Stephen Adolph" <twospruces at gmail.com>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Friday, June 11, 2010 2:56 PM
> Subject: Re: [Coco] Replacing Dynamic RAM with Static RAM
>
>
>> I have a large quantity of 1M x 16 3.3 V SRAM chips, and a large
>> quantity of CPLDs.
>>
>> These parts are perfect for such a card.
>>
>>
>>
>> On Fri, Jun 11, 2010 at 3:06 PM,  <sales at gimechip.com> wrote:
>>>
>>> I just noticed the mention of using a single 2-Meg SRAM. That's what I've
>>> been working on, but the SRAM is 1024x16 for a total of 2-Megs by eight.
>>> The
>>> GIME has a 16-bit databus (sort of). Even bytes are in one bank and odd
>>> bytes in the other, thus a 16-bit SRAM or two 8-bit SRAMs are ideal. It
>>> can
>>> be done with an 8-bit wide SRAM as well, I suppose, but I haven't tried
>>> that
>>> yet.
>>>
>>> I am using a 16x4-bit RAM array with associated multiplexing circuits to
>>> extend the MMU registers by 8-bits.
>>>
>>> Since I'm using Static RAM, no modified refresh is required, plus if the
>>> SRAM is battery backed, the various RAMdisk software can be non-volatile
>>> (although some of the RAMdisks initialize the disk automatically - that
>>> behavior would have to be patched out)
>>>
>>> The video can only exist within a 512K block - this is a GIME limitation.
>>> Using Tony's method, a register holds the Video Bank data. During a video
>>> cycle, the video bank data is presented to the RAM to select 1 of 4 of
>>> the
>>> 512K banks for video.
>>>
>>> The CPU, however, can access the entire 2-Megs via the normal paging
>>> method.
>>> During a CPU cycle the DAT register addresses are presented to the Static
>>> RAM.
>>>
>>> There's a little bit more to it than that (for example, the dual WE*
>>> signals
>>> must be accounted for - I've done this by multiplexing them and using A0
>>> to
>>> select which one passes to the SRAM for R/W* control - A0=0=even bank,
>>> A0=1=odd bank). This should be completed soon. I'll upload everything to
>>> coco3.com and maltemedia for any who want to make use of it.
>>> J&R
>>>
>>> ----- Original Message ----- From: <sales at gimechip.com>
>>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>>> Sent: Friday, June 11, 2010 1:50 PM
>>> Subject: Re: [Coco] Replacing Dynamic RAM with Static RAM
>>>
>>>
>>>> Yes, that's what these were for, but I also uploaded a file that uses a
>>>> 256Kx16 SRAM for the CoCo3 for 512K. It needs a bit of work. It's here:
>>>> http://www.coco3.com/community/2010/06/512k-simm-and-sram-files
>>>>
>>>>
>>>> ----- Original Message ----- From: "Stephen Adolph"
>>>> <twospruces at gmail.com>
>>>> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
>>>> Sent: Friday, June 11, 2010 1:21 PM
>>>> Subject: Re: [Coco] Replacing Dynamic RAM with Static RAM
>>>>
>>>>
>>>> Interesting.
>>>> I've got a background activity thinking about how to use a single 2MB
>>>> SRAM
>>>> chip.
>>>> Seems that this is a way to replace each individual DRAM with an SRAM.
>>>>
>>>> Similar, yet different. hmm more thinking.
>>>> Steve A
>>>>
>>>>>> On 6/11/2010 8:57 AM, sales at gimechip.com wrote:
>>>>>>>
>>>>>>> Over the past year, I've had some success at replacing DRAM with
>>>>>>> SRAM.
>>>>>>> I
>>>>>>> have posted some of the schematics and designs to CoCo3.com in these
>>>>>>> threads:
>>>>>>>
>>>>>>> http://www.coco3.com/community/2010/05/512k-upgrade-question
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> http://www.coco3.com/community/2010/06/4164-dram-sram-replacement-1-by-jr-of-gimechip-com
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> http://www.coco3.com/community/2010/06/4164-dram-%E2%80%93-sram-replacement-2-by-jr-of-gimechip-com-c19-march-2010
>>>>>>>
>>>>>>> It is relatively simple to demultiplex the multiplexed address lines
>>>>>>> and
>>>>>>> to replace DRAM with SRAM. The above links should provide a great
>>>>>>> deal
>>>>>>> of
>>>>>>> information on how I've gotten it to work.
>>>>>>>
>>>>>>> As soon as I get the rest of my documents together on the 512K, 1M&
>>>>>>> 2M
>>>>>>> CoCo 3 Static RAM upgrades, I'll get those posted as well. -J&R
>>>>>>>
>>>>>>> --
>>>>>>> Coco mailing list
>>>>>>> Coco at maltedmedia.com
>>>>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Coco mailing list
>>>>>> Coco at maltedmedia.com
>>>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --------------------------------------------------------------------------------
>>>>>
>>>>>
>>>>>
>>>>> No virus found in this incoming message.
>>>>> Checked by AVG - www.avg.com
>>>>> Version: 9.0.829 / Virus Database: 271.1.1/2931 - Release Date:
>>>>> 06/11/10
>>>>> 01:35:00
>>>>>
>>>>>
>>>>> --
>>>>> Coco mailing list
>>>>> Coco at maltedmedia.com
>>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>>>
>>>>
>>>> --
>>>> Coco mailing list
>>>> Coco at maltedmedia.com
>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>>
>>>>
>>>>
>>>>
>>>> --------------------------------------------------------------------------------
>>>>
>>>>
>>>>
>>>> No virus found in this incoming message.
>>>> Checked by AVG - www.avg.com
>>>> Version: 9.0.829 / Virus Database: 271.1.1/2931 - Release Date: 06/11/10
>>>> 01:35:00
>>>>
>>>>
>>>> --
>>>> Coco mailing list
>>>> Coco at maltedmedia.com
>>>> http://five.pairlist.net/mailman/listinfo/coco
>>>
>>>
>>>
>>> --------------------------------------------------------------------------------
>>>
>>>
>>>
>>> No virus found in this incoming message.
>>> Checked by AVG - www.avg.com
>>> Version: 9.0.829 / Virus Database: 271.1.1/2931 - Release Date: 06/11/10
>>> 01:35:00
>>>
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>>>
>>
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> http://five.pairlist.net/mailman/listinfo/coco
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.829 / Virus Database: 271.1.1/2931 - Release Date: 06/11/10
> 01:35:00
>
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco
>