*updating* 8088's

Allison ajp166 at bellatlantic.net
Mon Nov 19 22:03:23 CST 2007


>
>Subject: Re: *updating* 8088's
>   From: woodelf <bfranchuk at jetnet.ab.ca>
>   Date: Mon, 19 Nov 2007 20:39:49 -0700
>     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
>Chuck Guzis wrote:
>
>> Well, there's clock speed and then there's "apparent clock speed".  
>> Let's see, a 16MHz 80386sx is equivalent to what, a 10MHz 80286?

Actually it's teh other way around the 386 was more efficient than
286 for the same clock speed.


>So what speed does the memory run at is my question and how wide?

The SX narrows teh bus bandwidth so the memory is cycled either
faster to make up for it or has fewer idle states (bus availability).
that meant using 60ns 30pin simms.

>Playing around with homebrew micro design I am working on, a 500 ns
>memory cycle ( 2Mhz ) is about as fast as you can go with standard
>parts about 150 ns access time. My limiting factor is not memory
>speed but EEPROM and I/O chips dead slow speeds.

Those speed limits are consistant with pre 1978 parts for ram
and even in 1979 I had some semistatic rams that were 200ns.
Eproms were always slow and didn't break the 250ns barrier until 
around 82 but the mask roms were quite a bit faster.

I build with 6 and 10mhz z80s and 12mhz 8085s I have and theres 
little problem with finding static rams and Eprom (and EEprom) 
that can keep up. I say little problem as I can find plenty of 
parts that way too fast in non-DIP formats.  If I need faster 
I can easily find CMOS static rams in the under 25ns range 
(486dx used 32kx8 and even 64kx8 15ns parts for cache) and 
larger EE/Flash/Eproms in the sub100ns range.

Even back in 1982 I could get power hungry 2147(4Kx1) and 2167(16kx1)
parts in the 45ns range.  Drams even first out 4164s were under Tcy
of 300ns.  Old Eproms in the pre8K sizes (2716, 2732) were never fast
but 27C256s that do 150ns are really old parts and 27C010s I have 
are 150ns for the slow parts.

Zilog peripherals can be found still at 4mhz and the 8085/8088
(82xx) parts were good to 5mhz with later ones (82Cxx) good to 
125ns.


Allison

>> Cheers,
>> Chuck
>
>




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