Mike's PCjr Page

I use braid sometimes, but prefer a soldersucker, the braid uses alot of heat transfer to suck out the solder, this can lift pads and damage the chip. But it does work for some instances.

I am going out on a limb here, but spent the better part of the day reviewing the original Sprint design, and I think I may have found an issue.... Not willing to say for certain, I need to do a ground up design to see if I am right. Also need to find a complete data sheet for the 8284 chip.

more to come.

OK i am satisfied that the original Doug Design is good and my layout is ok..
I am getting a quote for boards then will get a batch and build up a few...
I also have a few V20-10 chips that I want to try a higher crystal, just to push the limit, and see how stable it is..

bagelswitch wrote:

Chuckphd53 wrote: (Below is a picture of Bagleswitch's PCSprint board install from an earlier post, this shows the hole in the mother board
that the DiskDrive plastic leg snaps into the hole
SO: the only way to install the original design for the IBM515x is to use the IC1 position with headers.

My board _just_ clears the drive support leg in the front, the fan shroud in the back, and the side of the case on the right. There's really no other way these components could be placed above the the existing 8284 location without obstructing anything, so that's what I did. I followed the Severson schematic exactly, only swapped the part locations in the physical layout (and let Eagle figure out the trace routing, I'm a novice) - I'll share the schematic and layout files I created somewhere later this weekend.

Eagle layout: https://1drv.ms/u/s!AqVrKLbX9W2f33vPB8P ... V?e=QcGFlG
Eagle schematic: https://1drv.ms/u/s!AqVrKLbX9W2f33ydk-I ... 9?e=1RAF56
Gerbers (these should work as-is at PCBWay): https://1drv.ms/u/s!AqVrKLbX9W2f33qoZON ... r?e=5ZHOYT

The new PC-SPRINT boards came in, I will be testing it this weekend and give a report on how it is working..

Ok here is the testing results using TOPBENCH test tool

Basic system w/ sidecar 512K mem
DOS boot V4.0

8080 Processor Original
Sprint OFF Score 4
Sprint ON Score 6

V20-10 Processor
Sprint OFF Score 5
Sprint ON Score 8

So it looks like a success.

I Still want to try a larger Crystal with the V20 chip, I will try this next week.

I know there are a number of folks that want this board, so I can do this two ways.
one is a kit, I will solder all the smt parts, but the thru hole header etc will come as parts to be done by you.
This will make it easier to mail and not get damaged.
If you do not want to solder the headers I will have to mail the completed unit in a USPS priority Box.
this will ensure it does not bet pins bent etc. But this is $7 just for shipping...

I have some of the 8284 chips coming but guessing I will need more.

Let me put a package together and get a price for these..
just FYI I will not Mark up the cost, It will be my cost, its for the Jr Folks ! (as it should be)

Also I have ordered some solder wick and solder suckers from China, these are cheapys but thought
there may be something the folks may want in the kit, I think I have 5 each coming.
Also I can include a small length of solder in the kit, I will put one together and take a picture...

I used my solder sucker to get the 8284 chip out, and still had to work it a little to free it up...just FYI.

Lastly I have a couple V20-10 chips, but depending on the tests with the larger freq crystal results I may only
include these with the high end Sprint brds, if they work...
(anyone have a memory tester for this high speed test)


Parts are still in ship mode hope to have items next week then I will post another email
with email to send kit requests..

any questions let me know..

Chuck

YMMV of course, but with my boards I haven't had any success above 8MHz (using a 16MHz-capable V20).

With any crystal I tried faster than 24MHz, the system will cold boot, and even run topbench, but anything that involves much disk or memory access results in a hang.

w/ a 24MHz crystal, things are rock-solid.

What flavor V20 are you using ?

Also, only the 8284A1 can be used for the V20-10 the 8284's pulled from the Jr won't handle the higher speeds..

bagelswitch wrote:YMMV of course, .

Maybe my age is showing, but YMMV ?????

hope we are not getting so lazy that shortcuts on this board exclude some from understanding what the hell we are all doing .... Grin

Your Mileage May Vary . . .

And yes, I'm using 8284A1 clock generators for attempts above 8MHz.

The V20 I'm using is a D70108HCZ-16: https://www.alldatasheet.com/datasheet- ... CZ-16.html