Submission for comp-unix-microport

[The Daily Fishwrap]

Path: tolerant!voder!apple!rutgers!njin!princeton!siemens!drexel!ipc
From: ipc at drexel.UUCP (Image Processing Center)
Newsgroups: comp.unix.microport
Subject: Re: Ramdisks and microport unix
Summary: INBOARD and bus memory.
Message-ID: <845 at drexel.UUCP>
Date: 4 Jan 89 10:56:18 GMT
References: <732 at inuxh.UUCP> <5022 at b-tech.ann-arbor.mi.us>
Distribution: usa
Organization: Drexel University, Phila., Pa.
Lines: 27

In article <732 at inuxh.UUCP> dyson at inuxh.UUCP (John Dyson) writes:
 
>the top instead of from the bottom.  Since I have an Inboard/386 and
>only 3MB of its memory is 32bits and the top of the memory is supplied
>by and Above Board, the ramdisk also keeps programs from executing from
>the slow memory.  The /unix runs in slow memory also, but I have not noticed

Does any brand of '386 unix automatically allocate it's buffers (and 
maybe kernel space) starting from upper memory?  If not, can it be 
made to do so?  
> 
You will find that the INBOARD works very well with bus memory if you
perform the ollowing modifications:

1) Increase the bus speed to 10mhz. This usually requires only burning
faster roms.
2) Replace the memory board with an Everex RAM 3000, which can run with
0 wait states at up to 10mhz using ordinary 120ns parts, and costs less
than $100 unpopulated.

The net improvment is to halve the access time of bus memory, according
to the following formula:

     Tnew = Told (8/10) X (2/3) = 0.533 Told

The result is that the difference in throughput will be negligible, and
you won't have to scheme about memory allocation.