Pdp11/23+ EPROM upgrade

Roe Peterson roeapeterson at gmail.com
Fri Feb 6 05:41:12 CST 2015

> On Feb 6, 2015, at 4:11 AM, Johnny Billquist <bqt at update.uu.se> wrote:
>> On 2015-02-05 19:49, Roe Peterson wrote:
>> I want to update the EPROMs on my 11/23+, which currently has 2716s.  I'm going to need 64k chips, and I understand 2764s won't work on this board.
>> What are my replacement options?  I have a fairly capable programmer, it can probably handle anything with 64k capacity.
> ??? I don't get it.
> 64K chips? The 11/23 currently uses the 2716, which is what? 2K (bytes)? I doubt there are any more address lines going to that chip in the first place, and second, the memory is mapped in the I/O space which have a total of 8K, and that should cover not only the boot rom, but also all CSRs of all devices you have in the machine. A 64K chip is going to be totally meaningless.
> So why are you looking for a 64K chip? (27512 I would assume that would be...)

2716 = 16k bits = 2kbytes X 8 bits
2764 = 64k bits = 8kbytes X 8 bits

The latest rom images for the 11/23+ require 8kbyte chips.

>    Johnny
> -- 
> Johnny Billquist                  || "I'm on a bus
>                                  ||  on a psychedelic trip
> email: bqt at softjar.se             ||  Reading murder books
> pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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