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PC SPRINT CARD OVER CLOCK FOR 8088 XT PC COMPUTER 5160 8 bit xt IBM 5150 5160

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gerrydoire

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Aug 25, 2008
Messages
1,145
There is one of these things for sale on Ebay:

April 14th, 2012

Item number:

261000764118


My question is: Does this thing actually work?

If it does, by the looks of it, it don't look like it would be hard to reproduce, improve?

Maybe a project for the IDE XT Guys, jusy putting that thought out there :D
 
Yes, it works.

Original docs can be found here:



I created PDFs for the artwork files, which are designed for an Epson compatible printer in graphics mode.

Matt Carpenter did a version of this a few years ago for the PCjr. It is fairly well understood.


Mike
 
FWIW,. the seller's a good guy - I've been communicating with him privately for about two weeks. We swung a good trade for an Adlib card that he had listed. He thought it was great to find someone to talk tech with, and then I told him about this place - to my knowledge he hasnt' joined yet, but he says he will... we'll see!

Either way... he's a good guy to deal with. And I can tell you, the BIN was just as test of the waters, to see if he'd get a bite (most of his prices are that, I think - that's not to say that he doens't have a specific value in mind for them, but his BINs are what he'd like to get in a perfect world, not what he'd accept)
 
I was hoping that by posting that, I would dramatically move the market for the used versions. ;-0
 
The auction may be slightly misleading, because using a 20MHz clock would give a CPU effective clock speed of 6.66MHz. The 8284 divides the clock crystal by 3. Moreover, it only works in systems with a discrete 8284.
 
gerrydoire said:
Is one of these things worth using, any major drawbacks?
Click to expand...

That depends on how wedded you are to the original speed of your machine. The worst possibility is that you shear a pin off an 8284 or 8088/V20. However, as mbbrutman has schematics available, you could easily build one for $30 worth of parts.
 
I wanted to see how the PC SPRINT worked to see if it could be used with a 6502 cpu, when I found it years ago and only recently got a dot-matrix printer to have a go printing it, no need now, lol am I right it just overclocks the motherboard ram and cpu?
 
rorypoole said:
I wanted to see how the PC SPRINT worked to see if it could be used with a 6502 cpu
Click to expand...

It is not, unless your 6502 system uses 8284 clock generator to generate CPU clock :)

rorypoole said:
am I right it just overclocks the motherboard ram and cpu?
Click to expand...

Yes it does overclock everything except of system timer and OSC clock (which present on ISA and used by some extension cards, e.g. CGA and Adlib).

The board replaces 8284 clock generator with two. First one generates clocks based on 14.31818 MHz crystal (just as the standard IBM PC / XT do), this clock is used to generate PCLK (used by timer), and for normal (non-turbo) CPU clock. The second one generates clocks based on the second (22 MHz?!) crystal, which is used for turbo mode CPU clock. Remember that the CPU clock is derived by dividing the frequency by three, so the actual CPU frequency will be 4.77 MHz and 7+ MHz respectively.

It still makes me wonder how it works with DMA... 8237 DMAC is rated for 5 MHz and overclocking it doesn't work really well. Perhaps 7 MHz is not that much of overclock.
 
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