🚀 go-pugleaf

>In article <3842@utah-cs.UUCP>, halff@utah-cs.UUCP (Henry M. Halff) writes:
>> Several clones advertise that they use a 8088-2 processor.  Can
>> anyone tell me what the difference is between an 8088-2 and an
>> 8088 is?
>> 
>An "8088-2" includes functions/circuits that an 8088-based machine requires a
>additional (support) chips for.  While an 8088-2 -based machine also requires
>support chips, the overall logic chip count is reduced substantially - thereby
>reducing cost, size, and (usually) failure points.
>  g. pavlov, fstrf, amherst, ny.

Hold on, there!   The 8088-2 part is functionally the same as the 8088.  It
is spec'd to run at up to 8 MHz, whereas the 8088 is only spec'd to run up
to 5 MHz.

G. Pavlov's reply sounds like s/he was describing the 80188 part, which does
indeed pull alot of the required outboard support logic onto the chip (clock
gen, timers, rupt controller, DMA, etc).  The 80188 also provides a *few*
additional instructions (push-all/pop-all, variable length shifts, etc).

The clones that Mr. Halff refers to likely run at 8 MHz, though they probably
have a switch or mode in which they run at 4.77 MHz (necessary for *true*
compatibility with brain-damaged s/w that uses s/w timing-loops).



To anticipate a probable question ... yes, you can replace an 8088 with an
8088-2, *BUT* it will not increase the performance of your system, as the
processor will still be clocked at the 4.77 MHz rate (for a true PClone).
Increasing the clock on a PClone is an "iffy" proposition, as the rest of
the system was probably not designed for higher speed operation.

A very reasonable way to boost vanilla PClone performance a bit (10-15%,
overall), is to replace the 8088 with a NEC V20 processor.  While the
clock will still be 4.77 MHz, the NEC chip performs many operations in
fewer cycles than does the 8088.

As a bonus, the V20 includes the additional instructions that the 80188 has,
plus it includes several "new" instructions that provide bit operations,
packed decimal arithmetic, and a few others.  The V20 also has an "emulation-
mode" for the 8080 uP instruction set, and can execute 8080 code directly
(of course appropriate control and dispatch s/w is needed to use this in
a system).

There is an EXCELLENT two-part article on the V20 (and the V30, which is
the 8086 replacement) in the Nov/Dec '85  and  Jan/Feb '86  issues of
"Micro/Systems Journal" if anyone is looking for more information.

Currently, V20's go for about $20 (look at the ads in the back pages of
BYTE), though I've seen them locally for around $15.  As a suggestion,
if you plan to make this upgrade, try to get the 8 MHz version of the
V20 (even if it will only be run at 4.77 MHz);  it seems that there *is*
a slight difference in the spec for the clock duty-cycle that *could* cause
a problem (erratic operation, etc.) if the 5 MHz part is used (the NEC
part-numbers for the 8 MHz parts are: uPD70108C-8 and uPD70108D-8 for
plastic and ceramic packages, respectively).

Only problem I've had using a V30 in place of an 8086 is a couple of
programs that use those brain-damaged s/w timing-loops I mentioned earlier.
Gurrrr!!!


Disclaimer:  I don't work for (or have any connection with) Intel, NEC, BYTE,
             or Micro/Systems Journal in any way except that I've used their
	     chips and read both magazines.  I *do* think that $15-$20 for a
	     10%-15% performance boost on a 8086/8088 based machine is one
	     of the best values around today.

/kim
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