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Ibm pc jx

vwestlife said:
The JX was quite obviously an attempt to compete with the NEC PC-98 series, no? Both had optional hi-res graphics and Kanji support. But by 1985, NEC added 8 and 10 MHz V30 processors and FM synthesis sound to the PC-98 series, while the JX was stuck with a 4.77 MHz 8088 and 3-voice PCjr sound.
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From a random Japanese page I found, it did seem like buying an NEC PC-98 system was the smarter move back then.

And once you knock off the specialised Kanji support - you're left with a bit of an unfocused mess for the Aus/NZ market. Priced too high for the average home computer at the time (8 bitter), and it's advantages didn't make sense for the small business market it aimed at.

For the office...
- no choice in video options, so you'll be stuck doing 640x400 and 320x200 stuff on RGB* instead of crisp MDA
- no real use for 3 voice sound
- no real use for two joystick ports
- no real use for wireless keyboard
- once the serial port is installed, you're out of slots

But one thing to keep in mind is I don't think this was a very big venture for IBM, but rather them dumping a bunch of stuff at Panasonic and seeing what they could do with it and then reusing it as a cheap entry level setup for AU/NZ. So I'm not sure if it earns a "fail" or a "flop" - it's possible it did all it was expected to do.

NB: Just my thoughts, if anyone disagrees feel free to reply.

* just a side note about the display, it has a light grey tube, which makes it feel more like an Amiga 1084S than an IBM 5153

Oh and for anyone who hasn't seen it, the IBM JX advert (probably from Australia)
 
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I imagine the $1,100 rebate was only if you bought ten of them :p

But I was doing a little digging and I think the IBM JX was somewhat price competitive here in 1986 - but was in that "in between zone" between home computer and IBM clones. Looking at Bits & Bytes I can see 256K XT clones in the 2 to 3K range - many with only a 3 month warranty.
 
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So what are the QFP chips on the board?

Curious if the system requires a patch to boot later DOSes or if the video RAM is separate from system RAM.
 
MikeModifed said:
FWIW (NOT mine!): http://www.ebay.com/itm/VINTAGE-IBM...18?pt=LH_DefaultDomain_15&hash=item487c3264de

Mike
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I ended up buying this if anyone was curious. The owner still wanted full price as (understandably) the machine isn't much use without the floppy drives, but was willing to pull them out to save on shipping. I just paid the full shipping price, might as well get a few spare parts while I'm at it. Postage ended up costing the same as the system unit, which is more than I wanted to spend, however I was a little pessimistic that I'd get any more JX parts opportunities in the future at lower prices, and given the condition of my machine, I really wanted it on display with disk storage.

Once the second JX unit arrives and the drive module is out, I'll pop the blanking plate in it, so it'll still be an operational unit but reverted back to a JX1 configuration.
 
Postage ended up costing the same as the system unit, which is more than I wanted to spend, however I was a little pessimistic that I'd get any more JX parts opportunities in the future at lower prices
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Outrageous shipping; but I think is the right move. Now you have a lot of valuable spares.

Please tell me someone tried to grab this! A JX program would likely run on the PCjr, and finding new PCjr-specific programs is pretty rare these days.
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I missed this one, I'm low budget lately; but if I'm not wrong it ended up for 4800JPY, about $40 ;-)
 
Just before six AM this morning, my dog went completely bananas, but then suddenly a JX appears...

CC-Z6UXUgAApDSh_zpsjavsqtlp.jpg


Something that may make some of you smirk - yesterday I found a third, in NZ, with the 3.5" drives AND 5519 5.25 attachment.
I just wish I could see the future before I hit Buy Now on ebay. Trying to get that third unit as well - for the 5519 hat - but may end up selling a unit as 3 feels a bit greedy - just as long as I can find a keyboard/display solution for it.

But we'll be rocking some JR games tonight :cool:
 
Nice find!

My keyboard is now disassembled and I'm trying to figure out the pinout. I suppose it'll be very close to the one found in the JR.
 
Awesome :) Would be a very handy piece of information for other people too (the keyboard port that is).

Well the Australian JX does not beep, it just kind of makes a squeal noise out the speaker, the upshot to this was I didn't feel bad about stealing it's floppy module.
I've reassembled mine with the original 85 BIOS, and the new floppy module.

Some things I noticed:
- The BIOS ticks over 384KB, but like the JR you need to run a program to see more than 128KB in DOS
- It starts in 40 column mode for no good reason, there is no TV out, add "MODE CO80" to your boot disk I guess - it displays nice and clear
- the BIOS isn't limited to 40 tracks, it double steps on purpose, so you can't even boot off a 720KB disk because "Track 1" is now "Track 2"
To create a boot disk I took a 360KB image of MS DOS 3.2, and used ImageDisk to write with Double Step turned on

It sort of seems like they didn't fix anything, and added another annoyance? Will test out the 1986 BIOS and see what changes.

I'm going to switch the BIOS for the 1986 version that was inside the Australian JX - and see what changes.

Edit: upgraded BIOS to 1986 version, I can now boot from 720KB floppies OR double stepped 360KB - however if the machine starts from a double-stepped 360KB floppy it appears it retains the "double step" setting. So if you want to use 720K, you need to boot from 720K.
 
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That BIOS upgrade sounds great!. I need to check my own BIOS version; but I'm sure that it will be the old one, if so I would love to burn the new one into my JX.
 
Some more fun facts:

- uses a standard twisted 34 pin floppy cable - but the drive selects are also switched on the controller - so straight + DS1 jumper = A drive, and twisted + DS1 jumper = B drive.
- you can plug an everyday 1.44Mb drive in and it'll work as a 720Kb with no problems (just not quite tall enough to fill the gap correctly)
- drives are easily removed by sliding the drive backwards and lifting out, well they should be, but some engineer (at least on mine) made the bracket about 3mm too long so it hits the FDC PCB (genius).

I've also not been able to get it to format 720KB, just boot and read 720KB disks.
One of my floppy drives appears to be on the point of failure - working correctly on my 386SX, but in the JX the motor rarely turns on and when it does, only one head works - capacitors perhaps?

I'll make some images of the ROMs at some point.
Would be keen to get a copy of JX DOS 2.1 if anybody has it? Currently booting generic MS DOS 3.20. Will be trying out "JRCONFIG" soon to see if I can get more than 76KB RAM Free in DOS for the mean time :)

Update: JRConfig does work, however do not use the /S0 option, bad things happen if you do. Started up Leisure Suit Larry - 3 voice sound + 16 color - no problem.
 
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On a PCjr, it is possible to do some low-level debug by holding down a combination of joystick buttons. Doing this it will spit out some post codes to the serial port if your display is dead. Not sure if the JX has this facility or not, but it wouldn't surprise me since they seem fairly similar. I used this while resurrecting my PCjr. On it though it would at least beep, but display was dead. It ended up being the CAS delay line.
 
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