Image Map Image Map
Page 1 of 2 12 LastLast
Results 1 to 10 of 19

Thread: Z80 speed

  1. #1
    Join Date
    Mar 2020
    Location
    Wayne National Forest
    Posts
    126

    Default Z80 speed

    Roy Soltoff once said to me that main reason for xlr8 was additional RAM.

    If it were speed only the user wanted, there were Z80s faster than 64180. I have been looking around and fastest chip I see for Z80 is 10 Mhz made by Zilog.

    For a real Z80, does this sound like fastest chip? I did read a rumor of a 20 Mhz but have been unable to find this chip.

    Thanks

    Daniel

  2. #2

    Default

    The Z84C0020 is a 20MHz Z80 available in DIP-40, PLCC-44 & QFP-44 footprints.

    Rather than the original 64180, there is the Z180 available in speeds up to 33MHz (Z8S18033*) and it's approximately 12% faster than a Z80 at the same MHz on the benchmarks I've tried. For even faster speeds there's the eZ80 at 50MHz which has reduced instruction cycles and pipelining which yields about the equivalent of a 160-200MHz Z80 depending upon instruction mix.

  3. #3
    Join Date
    Mar 2020
    Location
    Wayne National Forest
    Posts
    126

    Default

    Quote Originally Posted by WSM View Post
    The Z84C0020 is a 20MHz Z80 available in DIP-40, PLCC-44 & QFP-44 footprints.

    Rather than the original 64180, there is the Z180 available in speeds up to 33MHz (Z8S18033*) and it's approximately 12% faster than a Z80 at the same MHz on the benchmarks I've tried. For even faster speeds there's the eZ80 at 50MHz which has reduced instruction cycles and pipelining which yields about the equivalent of a 160-200MHz Z80 depending upon instruction mix.
    Yes, I had excluded eZ80 and other because they are not 100% binary compatible. I am not sure but I think Z180 is binary compatible per Zilog.

  4. #4
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,060

    Default

    I think the big issue with the eZ80 is less that it's not strictly binary incompatible, it's that its internal I/O stomps on top of the addresses used by the TRS-80 and isn't relocate-able. The Z180 also has built-in I/O but my vague recollection is it all resides starting at ports 0x00h, which doesn't conflict with the TRS-80's internal hardware. (It might conflict with some devices that connect externally.)
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  5. #5
    Join Date
    Mar 2020
    Location
    Wayne National Forest
    Posts
    126

    Default

    Quote Originally Posted by Eudimorphodon View Post
    I think the big issue with the eZ80 is less that it's not strictly binary incompatible, it's that its internal I/O stomps on top of the addresses used by the TRS-80 and isn't relocate-able. The Z180 also has built-in I/O but my vague recollection is it all resides starting at ports 0x00h, which doesn't conflict with the TRS-80's internal hardware. (It might conflict with some devices that connect externally.)
    undocumented instruction binary compatibility was not maintained.

    Normally that should not be a problem but sometimes you will find it used especially in older code.

    Yes, for Z180 and eZ80 alike, any added I/O would not be strictly binary compatible since Z80 had none. No matter where they located it, someone would have a conflict. Best would be to allow user to relocate onboard I/O.

  6. #6
    Join Date
    Jan 2014
    Location
    Western North Carolina, USA
    Posts
    1,403

    Default

    Quote Originally Posted by Eudimorphodon View Post
    I think the big issue with the eZ80 is less that it's not strictly binary incompatible, it's that its internal I/O stomps on top of the addresses used by the TRS-80 and isn't relocate-able.
    Speaking from the point of view of having a little bit of experience with the eZ80, this is indeed the greatest obstacle; there are ways of forcing addressing external-to-the-chip I/O ports, but if you want to output a 0 to an external-to-the-chip port you can't use the straight OUT instruction. The total lack of DRAM refresh also makes it less than ideal for a Z80 replacement.

    The Z180 also has built-in I/O but my vague recollection is it all resides starting at ports 0x00h, which doesn't conflict with the TRS-80's internal hardware. (It might conflict with some devices that connect externally.)
    HD64180/Z80180/Z8S180 can have their internal device addresses set to one of a few starting addresses, but otherwise you have to do special magic to address off chip I/O in that range (special magic = make sure A<>0 for IN/OUT instructions using A, and B<>0 for I/O instructions using C register indirect).

    And even though I have a soft spot in my heart for the grand old Z800/Z280, the fact is, other than the lack of RAS-only row-address-counter DRAM refresh of the Z80 and '180, the ultimate Z80 with the most compatibility is the current production ( https://www.digikey.com/en/products/...8018FSG/928902 ) 16/32 bit Z380 MPU @ 18MHz, like these:

    Z80380-lro.jpg

    Yeah, Z380 can address 4GB of RAM, although at 18MHz you probably wouldn't want to. Highly efficient, almost as efficient as eZ80, but tops out at 18MHz to eZ80's 50MHz. But, Z380 is currently stocked and is an active item in Zilog's catalog. It's a CPU only, so no on-chip peripherals to speak of. I wish I had time to put together a Z380 system with my hand-soldered sample you see in the photo; Real Life (TM) prevents much of that for me right now. Maybe one day; I have four chips, two not soldered to carriers, and some schematics drawn. Likewise the eZ80; I have the beginnings of an eZ80 with VGA output and PS/2 input built on the Zilog modules, a hand-wired interposer, and an Altera DE1 FPGA board. Maybe one day I'll get enough time to finish it.
    --
    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

  7. #7

    Default

    Yeah, there are definitely proper Z80s running at high speeds. IIRC my Zeta SBC has a 20MHz Z80 in it.
    Computers: Amiga 1200, DEC VAXStation 4000/60, DEC MicroPDP-11/73
    Synthesizers: Roland JX-10/SH-09/MT-32/D-50, Yamaha DX7-II/V50/TX7/TG33/FB-01, Korg MS-20 Mini/ARP Odyssey/DW-8000/X5DR, Ensoniq SQ-80, E-mu Proteus/2, Moog Satellite, Oberheim SEM
    "'Legacy code' often differs from its suggested alternative by actually working and scaling." - Bjarne Stroustrup

  8. #8
    Join Date
    Jan 2014
    Location
    Western North Carolina, USA
    Posts
    1,403

    Default

    Yeah, 20MHz Z80 in DIP, QFP, and PLCC are also current production. Plasmo has gotten the 20MHz Z80 overclocked quite a ways.
    --
    Thus spake Tandy Xenix System III version 3.2: "Bughlt: Sckmud Shut her down Scotty, she's sucking mud again!"

  9. #9
    Join Date
    Aug 2017
    Location
    New Mexico, USA
    Posts
    143

    Default

    Zilog specifications were very conservative. I routinely overclocked Zilog parts and found surprises.

    I've designed rev 1.3 of ZRCC with fast RAM to check out overclocked Z80, https://www.retrobrewcomputers.org/d...o:zrcc:zrcc1_3

    The fastest Z80 is 33MHz, it takes 24 minutes to complete zexall.com under CP/M2.2

    Bill

    PS, I have a Z280 on my desk right now driving a VGA text display and the oscillator is 35.96MHz or 17.98MHz CPU clock (the rated CPU clock is 12.5MHz).

  10. #10
    Join Date
    Mar 2020
    Location
    Wayne National Forest
    Posts
    126

    Default

    But if I read correctly some instructions on Z180 were removed such as halt, IM 0 etc. So in a pure definition it is not binary compatible.

    That leaves only Z80 line that is 100% compatible. I am guessing 33 Mhz version did not change anything as far as instructions go.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •