| Re: ZRCC, Z80+RAM+CPLD+Compact Flash [message #7953 is a reply to message #7695] |
Tue, 08 September 2020 16:17   |
plasmo
Messages: 916
Registered: March 2017
Location: New Mexico, USA
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Senior Member |
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What has started out as discovery of a forgotten batch of fast RAM and my desire to check the design margin of ZRCC are becoming a long exercise in Z80 overclocking. RAM speed was the first limit, but at 30MHz or greater, the CF disk becomes the limit. This is what a 33MHz ZRCC looks like after 2 iteration of pc boards. The 25ns 128KB RAM is fast enough for Z80 to run zero wait state at 33MHz and replacing CF disk with disk-on-module also allow zero wait access of the mass storage. The pc board is 2-layer, 50mm X 76mm.
To verify the board really work at 33MHz, I run memory diagnostic, run CP/M, do disk copy with verify in CP/M, and run the instruction test zexall.com. 4 out of 5 boards passed at 33MHz. The 5th board failed zexall.com tests. Once the Z80 of the 5th board is replaced with another, it passed all tests at 33MHz. So I think I've reached speed limit of Z80.
Power consumption is 160mA at 5V.
https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:zrcc:zrcc1_3
[Updated on: Tue, 08 September 2020 16:20] Report message to a moderator |
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| Re: ZRCC, Z80+RAM+CPLD+Compact Flash [message #7985 is a reply to message #7953] |
Fri, 25 September 2020 10:48 |
jaevans
Messages: 2
Registered: October 2018
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Junior Member |
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Hopefully, this is an appropriate question for this thread.
I am trying to transfer files through Teraterm to the ZRCC but have not gotten xmodem on the ZRCC (in either CP/M 2.2 or 3.0) and xmodem through Teraterm by manually typing the commands to transfer a file. If I create a macro file similar to the newCF.ttl file to transfer a simple small text file, the transfer succeeds.
So, I am looking for help in using xmodem on the ZRCC to transfer files to the drives.
Thanks in advance.
John - Colorado Springs, CO
[Updated on: Fri, 25 September 2020 10:50] Report message to a moderator |
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| Re: ZRCC, Z80+RAM+CPLD+Compact Flash [message #8210 is a reply to message #7987] |
Tue, 19 January 2021 17:35 |
plasmo
Messages: 916
Registered: March 2017
Location: New Mexico, USA
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Senior Member |
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As mentioned in the original post, some 20MHz Z80 can run to 33MHz, but as I lowered the supply voltage toward 4.75V, fewer and fewer Z80 can pass memory test, CP/M disk copy, and zexall instruction test at 33MHz. Roughly 10% is good to 33MHz at 4.75V. However, at 29.5MHz about 9 out of 10 Z80 are good. Because I believe 29.5MHz ZRCC is producible, I have added a new section of software in ZRCC v1.3 homepage specifically for 29.5MHz as well as automated software installation. I also listed the testing procedures to verify proper operation.
https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:zrcc:zrcc1_3#software_for_295mhz_clock
Bill
PS, I have built up all ten rev 1.3 boards and auction them off on eBay starting from $1; one a week until they are all gone. They are selling well, but you guys know how to order the pc board and build them yourselves. I'm happy to help you with construction and debugging if you've ran into problems.
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