new 512k side car

Hardware questions and modifications

new 512k side car

Postby Iudex » Mon Aug 26, 2013 5:11 pm

I just purchased a modified 512k side car off ebay. It seems as though it could be bad. When I use jrconfig.sys it only displays the ram on the post screen 384k but says ram above 640K is available and to use /L in my config.sys.

config.sys looks like:
device=jrconfig.sys /L

and still no luck.

Any suggestions?
Iudex
 
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Re: new 512k side car

Postby James » Tue Aug 27, 2013 7:44 am

Modified in what way? 128K to 512K? Starting Memory Address?

Is this your only memory sidecar? If it was just a total memory modification it is still hardwired to start a 129K

Assuming this is your only memory sidecar there should be no memory above 640K. 128K + 512K = 640.
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
James
 
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Re: new 512k side car

Postby Iudex » Tue Aug 27, 2013 8:10 am

According to it's ebay description it was an ibm 128 side car modified to 512k. It came without an outer cover (just the board) so I put it in a spare out cover. jrconfig need 256k to run so I have tried the 512k sidecar with tecmar captain (128k) and cadet (also 128k). In addition to this I have tried the setup with my legacy "blinkenlights" drive (which includes 256k). Either configuration should give me a total ram of 896K.
I am aware that the pcjr will not post more than 640K and jrconfig should not post more than 768K. Regardless I only see 384k in the intial post screen and 384K in jrconfig with the message ram above 640k detected.

Off topic, but for some reason the tecmar side cars and the legacy drive both attached (for a total of 512k itself) only ever posts 384k where either one or the other is not recognized.

Thanks for the reply
Iudex
 
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Re: new 512k side car

Postby James » Tue Aug 27, 2013 8:52 am

Unless the IBM sidecar was specifically modified to start at 385K, it is not compatible with the Tecmar Capatain and Cadet. Both the Tecmar's and IBM sidecar's memory is hardwired to start at 129KB . I don't know how hard it would be to modify the IBM Sidecar to start at 385K but I believe that is what would be required to have these two work together. I believe it is the same situation with the Legacy "blinkenlights".
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
James
 
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Re: new 512k side car

Postby jmetal88 » Tue Aug 27, 2013 9:19 am

James wrote:Unless the IBM sidecar was specifically modified to start at 385K, it is not compatible with the Tecmar Capatain and Cadet. Both the Tecmar's and IBM sidecar's memory is hardwired to start at 129KB . I don't know how hard it would be to modify the IBM Sidecar to start at 385K but I believe that is what would be required to have these two work together. I believe it is the same situation with the Legacy "blinkenlights".


Yup, I agree with that. If your board was modified to have 512k, you should be running it by itself without those other sidecars if you want to really test it.
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Re: new 512k side car

Postby Iudex » Tue Aug 27, 2013 1:10 pm

Thanks for all the replies. My original question was: since this new sidecar is not posting when the pcjr starts and jrconfig will not recognize it but says that I do not have enough ram, does this mean the sidecar is not working or should I try something else? Thanks.
Iudex
 
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Joined: Fri Oct 26, 2012 6:11 am

Re: new 512k side car

Postby James » Tue Aug 27, 2013 2:17 pm

Take all the sidecars off the PCjr except the IBM memory sidecar. If the PCjr counts to 640K, then it is working. JrConfig should recognize the 640K too at that point.
-PCjr (1989)-DOS 3.3, Racore Drive II, jrIDE-128 MB DOM, jrExcellerator, Tandy Mod, Serial Card, Combo v2, Config Plus, IBM Parallel Port, Megaboard, Xircom PE3-10BT
-PCjr (2001)-DOS 3.3, jrIDE-128 MB DOM, NEC v20, Parallel Port, Comswap, Xircom PE3-10BT
James
 
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Re: new 512k side car

Postby Iudex » Tue Aug 27, 2013 3:02 pm

Thank you for all your help.
Iudex
 
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Joined: Fri Oct 26, 2012 6:11 am


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