[Coco] 68764/68766 EPROMs

Mon Oct 5 21:52:50 EDT 2015

Could not open links, got 404 - not found.  Is this the same thing as the 24 to 28 pin adapter for FDC or is it a specific pin arrangement for the motherboard only?

I might be having 26-3134A CoCo 2 on the way in a few days.  It's likely to have a 24-pin ROM slot with Color BASIC only but from what I've read this model has some strange 24 pin ROM chip in a 28-pin socket but a 27128 can be installed if jumpers are set.  What's going on with that?

- Chad H
http://sites.google.com/site/cbhlab101/

-----Original Message-----
From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Zippster
Sent: Monday, October 05, 2015 7:20 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] 68764/68766 EPROMs

Hey guys,

I received some PCBs back today from OSH Park and  assembled an adapter.  They work great.  They fit perfectly on American CoCo2 motherboards and F boards, even D boards (barely).

Simple, cheap ECB ROM replacement for these machines.

- Ed

<https://drive.google.com/open?id=0B1sgl615FlGnUDRsa0J2ZVZwYkU <https://drive.google.com/open?id=0B1sgl615FlGnUDRsa0J2ZVZwYkU>>
<https://drive.google.com/open?id=0B1sgl615FlGnN0p3YTZxd0NtUEk <https://drive.google.com/open?id=0B1sgl615FlGnN0p3YTZxd0NtUEk>>
<https://drive.google.com/open?id=0B1sgl615FlGnRHVEMEhMcHlqSUE <https://drive.google.com/open?id=0B1sgl615FlGnRHVEMEhMcHlqSUE>>
<https://drive.google.com/open?id=0B1sgl615FlGneGNOQTNNOTB4RVU <https://drive.google.com/open?id=0B1sgl615FlGneGNOQTNNOTB4RVU>>

> On Sep 21, 2015, at 7:00 PM, Al Hartman <alhartman6 at optonline.net> wrote:
> 
> Very cool!
> 
> My burners will handle 68766 EPROMS, but being able to use a 2764 will help lots of folks.
> 
> Thanks for doing this!
> 
> -[ Al ]-
> 
> -----Original Message----- From: Zippster
> 
> I just started drawing an adapter up a few minutes ago.
> Cutting a deal for the proms to go with them.  They will be far less than $18.
> I have quite a few CoCos that could use an ECB, so it’s something I’ve 
> been intending to do anyway.
> 
> I’ll should have files off to OSH Park tonight or tomorrow, there’s 
> not much to an adapter like this.
> 
> - Ed
> 
> 
> 
>> On Sep 21, 2015, at 5:53 PM, Al Hartman <alhartman6 at optonline.net> wrote:
>> 
>> This is not for a disk controller. Ron needs an Extended BASIC ROM for a Coco he bought. I no longer have any masked ROMs, and offered to burn him one if he could get me the blank EPROMS.
>> 
>> But a 2764 with an adapter will cost as much as that 68766 for $18.00, unless Ron can wire one up himself.
>> 
>> Clearance isn't a problem for an ECB ROM.
>> 
>> -[ Al ]-
>> 
>> -----Original Message----- From: Arthur Flexser
>> 
>> P.S.  It is also possible to bypass the disk controller clearance 
>> problem by having a 28-pin 2764 or 27128 EPROM in a 24-pin disk 
>> controller socket with pins hanging off the end and other pins bent 
>> outward to not plug in, hand-wiring a few connections between things.  Not pretty, but workable.
>> 
>> Art
>> 
>> On Mon, Sep 21, 2015 at 6:33 PM, Arthur Flexser <flexser at fiu.edu> wrote:
>> 
>>> There have been various such adapters in the CoCo and non-CoCo 
>>> markets. I sold one with ADOS for a time.  Cloud 9 sells a 
>>> particularly low-profile one, though it is somewhat more expensive 
>>> than those sold by others. There is not quite enough clearance for 
>>> most adapters in the Tandy disk controllers--some have tried cutting 
>>> a hole in the plastic cover, or just living with the cover not quite 
>>> being able to snap shut (the screw will keep the cover from coming 
>>> off, and the controller can still be inserted in the cartridge slot.  
>>> Probably not great for the long haul to have pressure on the circuit 
>>> board, though.)  The Disto controllers, with their sheet metal 
>>> covers, have a bit more clearance.  The problem of clearance is 
>>> greatly magnified if you want to piggyback a SmartWatch real-time 
>>> clock underneath the Disk Basic ROM.  (I went with a 
>>> cutting-a-hole-in-the-cover method there in my own CoCo system.)
>>> 
>>> A consideration that also exists is that it may be harder to find an 
>>> EPROM programmer capable of programming the 6876x series than for the 27xx EPROMs.
>>> 
>>> Art
>>> 
>>> 
>>> On Mon, Sep 21, 2015 at 6:14 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
>>> 
>>>> Would it be more practical to make an adapter to plug in more 
>>>> common 27xx series EPROMs? I don't recall how much physical clearance is in there.
>>>> 
>>>> --
>>>> Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/
>>>> 
>>>> 
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>>> 
>>> 
>> 
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